Cytokines

Synopsis

Cytokines: An Encyclopedic Reference on Identity, Biology, Pharmacology, and the Natural-Ingredient Supplement Context

Preliminary Clarification: Cytokines as Biological Targets vs. Dietary Ingredients

Cytokines are not themselves botanical or dietary supplement ingredients in the conventional sense. Cytokines are small soluble factors with pleiotropic functions that are produced by many cell types as part of a gene expression pattern that can influence and regulate the function of the immune system. They are endogenous proteins generated within the human body. However, the term "cytokines" appears prominently in the dietary supplement marketplace in two distinct ways: first, as a reference to biological targets — meaning that certain natural plant-derived compounds are studied for their ability to modulate cytokine production or signaling; and second, in the context of exogenous cytokine preparations that have been developed for clinical pharmaceutical use. This article addresses both contexts comprehensively, beginning with the scientific identity of cytokines themselves, proceeding through their biological functions and classification, and then examining the evidence base for natural dietary ingredients studied in relation to cytokine modulation.

1. Identity and Chemical Nature

1.1 Definition and Nomenclature

The term cytokine (from the Greek cyto, meaning cell, and kinos, meaning movement) was proposed by Stanley Cohen in 1974 and refers to peptides, proteins, and glycoproteins which play a role in controlling the survival and death of cells, their growth and differentiation, as well as the effector functions in tissues and immune cells. Cytokines are a group of small proteins or glycoproteins, usually less than 30 kDa in molecular weight, produced by a broad range of cells, such as immune cells and fibroblasts.

Cytokines are produced by immune cells (such as macrophages, T cells, B cells, and natural killer cells) or other types of cells (such as endothelial cells, fibroblasts, and epithelial cells). They transmit signals between cells and regulate various biological processes, including immune responses, inflammatory responses, cell growth, differentiation, development, and death.

The term cytokine is a general name; other names are defined based on their presumed function, cell of secretion, or target of action. For example, lymphokines are cytokines produced by activated lymphocytes, monokines are cytokines produced by monocytes or macrophages, chemokines are cytokines with chemotactic activity, and interleukins were initially named for their ability to mediate interactions between leukocytes.

1.2 Molecular Characteristics

Cytokines are soluble extracellular proteins or glycoproteins that are crucial intercellular regulators and mobilizers of cells engaged in innate as well as adaptive inflammatory host defenses, cell growth, differentiation, cell death, angiogenesis, and development and repair processes aimed at the restoration of homeostasis. They represent small secreted proteins (10–30 kDa) that are typically produced by cells of the immune system upon activation, and which play pivotal roles in the development and control of immune responses.

Cytokines are usually too large to cross cell membranes and enter cells. They typically function by interacting with specific cytokine receptors on the surface of target cells. Cytokines mediate many important physiological functions including growth, development, wound healing, and the immune response. They act by binding to their cell-specific receptors located in the cell membrane, which allows a distinct signal transduction cascade to start in the cell, which eventually leads to biochemical and phenotypic changes in target cells. Generally, cytokines act locally.

1.3 Classification and Major Types

The classification of cytokines is problematic because so much remains to be learned about them, but they can be divided into five categories: interleukins, interferons, colony-stimulating factors, tumour necrosis factors, and growth factors. A more expanded classification is also used:

Interleukins (ILs): Interleukins are a large family of cytokines that function as key mediators of immune cell communication, regulating cell proliferation, differentiation, motility, and survival across both innate and adaptive immunity. The term interleukin was first introduced in the late 1970s to describe leukocyte-derived cytokines, with IL-1 identified as a leukocytic pyrogen and IL-2 as a T-cell growth factor. Since then, more than 60 cytokines have been designated as interleukins, and to date, at least 38 have been formally recognized (IL-1 through IL-38).
Interferons (IFNs): Interferons were first identified in 1957, where they were found to interfere with a viral infection. IFNs possess several important properties, including antiviral, anticancer, and immunomodulatory properties. Based on primary structures and target receptors, IFNs are categorized into three subtypes: types I, II, and III.
Tumor Necrosis Factors (TNFs): TNF helps regulate inflammation in the body. TNF also signals to immune cells that kill tumor cells.
Chemokines: Cytokines with chemotactic activity, directing cellular migration to sites of infection or injury.
Colony-Stimulating Factors (CSFs): Types include granulocyte colony stimulating factor (G-CSF), macrophage colony stimulating factor (M-CSF), and granulocyte macrophage colony stimulating factor (GM-CSF).

Proinflammatory cytokines promote inflammation, whereas anti-inflammatory cytokines help control and resolve inflammation to prevent excessive tissue damage. Cytokines can act alone, work together, or work against each other to achieve biological functions.

2. Historical Discovery and Scientific Development

2.1 Early History

The first steps of cytokine discovery were taken in the 1920s, when it was shown that the mechanism underlying "bacterial allergies" differed from protein anaphylaxis and that the supernatants of tissue sensitized to tuberculin amplified the reaction to old tuberculin. Approximately 30 years later, the fundamental class of proteins leading to these phenomena started to be unraveled when the first individual cytokines were discovered as the "endogenous pyrogen" (later classified as IL-1) and "interferon."

The field advanced significantly in 1966 when David, Bloom, and Bennett employed the capillary tube technique to demonstrate that antigens could stimulate sensitized lymphocytes in cultures to produce migration-inhibitory factor (MIF). This was followed by Dudley Dumonde's introduction of the term "lymphokine" in 1969, defined as "non-antibody mediators of cellular immunity generated by lymphocyte activation."

Stanley Cohen's proposal of the term "cytokine" (from Greek cyto, cell, and kinos, movement) in 1974 encompassed these soluble mediator substances produced by both lymphoid and nonlymphoid cells, recognizing their fundamental role in host defense mechanisms. A significant milestone in immunology and oncology came with the discovery of TNF in 1975 by Carswell et al., who identified it as a macrophage-derived factor.

The term cytokine was proposed by Cohen et al. in 1974 to replace "lymphokine," a term coined in the late 1960s to denote lymphocyte-derived soluble proteins that possess immunological effects. Since the latter designation misleadingly suggested that lymphocytes were the only source for these secreted proteins, the term cytokine slowly became preferred. Following the introduction of this general term, the Second International Lymphokine Workshop held in 1979 proposed the interleukin (IL) system of nomenclature to simplify the growing list of identified cytokines.

2.2 Modern Era

Coined by Stanley Cohen in 1974 to describe cellular substances that induced immune-cell-directed migration (chemotaxis) and activation, since that time there have been many new insights into these molecules and cytokines are now defined as regulatory proteins that modulate the immune system and inflammation. Cytokines are currently known to be more than 130 in number, and are small molecular weight (<30 kDa) key signaling proteins that modulate cellular activities.

There have been extensive developments on cellular and molecular mechanisms of immune regulation in allergy, asthma, autoimmune diseases, tumor development, organ transplantation, and chronic infections during the last few years. Better understanding the functions, reciprocal regulation, and counterbalance of subsets of immune and inflammatory cells that interact through interleukins, interferons, TNF-α, and TGF-β offer opportunities for immune interventions and novel treatment modalities in the era of development of biological immune response modifiers particularly targeting these molecules or their receptors.

3. Key Biological Functions and Mechanisms of Action

3.1 Cellular Communication

Cytokines are small cell-signaling protein molecules with several functions. Intracrine actions involve intracellular regulation of events within the cytoplasm and/or nucleus. Autocrine action is produced within the cell through surface cell receptors. Intercrine communication occurs between cells. Paracrine signaling is produced by soluble mediators through neighboring cells. Matricrine signaling occurs when cytokines are immobilized in the extracellular matrix by binding to proteoglycans, where they are stored in an inactive form.

Furthermore, cytokines have overlapping actions characterized by a very broad range of functions, including hematopoiesis, cell growth and differentiation, angiogenesis, tissue remodeling, wound healing, effector immune cell activity, and life/death decisions. Moreover, cytokines with endocrine action circulate in picomolar concentrations, but under the influence of strong immune activation circumstances, they can surge up to 1,000-fold (cytokinemia).

3.2 Signaling Pathways

Cytokines exert their effects by binding to specific cell surface receptors, which are typically transmembrane proteins responsible for transmitting extracellular signals into the cell and activating downstream signaling pathways. One popular cytokine signaling mechanism used by cytokines such as IL-2, IL-4, IL-6, IL-7, IL-10, IL-12, IL-13, IL-15, and the interferons begins with dimerization of receptor subunits.

In some cases, one cytokine can interact with a variety of different cell types and elicit different responses from each cell. In other cases, different cytokines can elicit the same response from a cell. Some cytokines are known to induce or augment the activities of other cytokines, and sometimes their interactions occur through a cascading effect; however, the regulation of and cooperation between these various chemical signals still remain unclear in many cases.

3.3 Pro-inflammatory vs. Anti-inflammatory Balance

During an infection, the body naturally produces pro-inflammatory cytokines as part of its defense mechanism. The healthy body balances pro-inflammatory cytokines with anti-inflammatory cytokines. However, if pro-inflammatory cytokines such as IL-1, IL-6, IL-8, IL-17, IL-23, Tumor Necrosis Factor-alpha (TNF-α), or Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) continue in the "on position" after the immune threat has ended, inflammation levels remain high. Long-term or chronic inflammation can negatively impact overall health, contributing to chronic pain, poor sleep quality, and unhealthy cardiovascular function.

In the context of immunoregulation and autoimmune diseases, cytokines can play either a pro-inflammatory or anti-inflammatory role, mediate a particular T and B cell response, or drive a disease process. Autoimmune diseases may be caused in part by cytokine- and chemokine-mediated dysregulation of T-helper (Th) cell subset differentiation.

4. Cytokine Storm: Definition and Pathophysiology

A cytokine storm (CS) is a rapidly occurring, complex, and highly lethal systemic acute inflammatory response induced by pathogens and other factors. The cytokine storm, a hyperinflammatory response, is characterized by the excessive release of pro-inflammatory mediators such as TNFα, INFγ, IL-1β, IL-6, and GM-CSF, and has been identified as a critical factor in the progression and severity of acute inflammatory conditions.

Patients with a dysfunctional immune response exhibit higher levels of pro-inflammatory and modulatory cytokines and chemokines like TNFα, INFγ, IL-1β, IL-2, IL-4, IL-6, IL-7, IL-9, IL-10, IL-12, IL-13, IL-17, G-CSF, GM-CSF, MCSF, HGF, and chemokines CXCL8, MCP1, IP10, MIP1α, and MIP1β. Targeting this cytokine storm is a novel, promising treatment strategy to alleviate this excess influx of cytokines observed at the site of infection and their subsequent disastrous consequences.

5. Body Systems and Health Areas Associated with Cytokine Activity

5.1 Immune System

Cytokines include chemokines, interferons, interleukins, lymphokines, and tumour necrosis factors, but generally not hormones or growth factors (despite some overlap in the terminology). Cytokines are especially important in the immune system, including in immune responses and inflammation. These interacting biological signals have remarkable capabilities, such as influencing growth and development, hematopoiesis, lymphocyte recruitment, T cell subset differentiation, and inflammation.

5.2 Cardiovascular System

Resveratrol from red wine has shown anti-atherogenesis properties mainly due to its anti-inflammatory properties. In vivo and in vitro studies (in murine and rat macrophages) showed that resveratrol inhibited COX and peroxisome proliferator-activated receptor gamma (PPARγ), and activated eNOS (endothelial nitric oxide synthase). Clinical studies have shown that dietary supplementations containing combinations of quercetin, riboflavin, resveratrol, pterostilbene, morin hydrate, tocotrienol, as well as nicotinic acid significantly decrease cardiovascular risk factors in humans.

5.3 Central Nervous System

The role of cytokines in the central nervous system (CNS) and neurological diseases remains understudied. The introduction of interferon-beta and anti-interleukin 6 (IL-6) or anti-tumor necrosis factor-alpha (TNF-α) therapies in clinical practice advanced the field of autoimmune neurology and provided direct support for the critical involvement of cytokines in CNS diseases.

5.4 Cancer and Oncology

Interleukins are key communicators between immune and non-immune cells, playing an important role in cancer development, progression, and control. They shape the tumor microenvironment by either promoting cancer growth or activating immune responses against tumors. These dual properties of ILs present opportunities to improve advanced immunotherapies, improving their effectiveness while minimizing side effects. IL-2 is being researched to be included in combination therapies for cancer treatment.

5.5 Autoimmune and Inflammatory Diseases

Natural products have been studied for their role in directed immune modulation, including in the management of Crohn's disease, ulcerative plaque psoriasis, rheumatoid arthritis, and colitis, among other immunological and inflammatory diseases.

6. Exogenous Cytokines: Pharmaceutical Preparations and Clinical Use

Although cytokines were originally identified as substances produced naturally in the body or endogenously by cells and components of the immune system, several types of cytokines are now obtained in large quantities from sources outside the body, exogenously, by means of genetic engineering and cell culture methodologies, which has made the treatment of many diseases possible. The main types of cytokines used in clinical practice are interferons, interleukin-2 (IL-2), interleukin-12 (IL-12), and granulocyte-macrophage colony-stimulating factors (G-CSF and GM-CSF).

Given their essential role in various important biological processes, cytokines have been identified as therapeutic candidates to treat a variety of diseases. However, native cytokines usually have a narrow therapeutic window and short circulating half-life, which largely hampers their therapeutic efficacy. The pleiotropic nature of cytokines also makes non-target cells activate and become involved, causing undesired toxicities.

The clinical use of cytokines has been restricted. This clinical translational challenge comes from two major characteristics of cytokines: they are highly pleiotropic, and in normal physiology, they are generally produced and act very locally in tissues.

7. Natural Dietary Ingredients Studied for Cytokine Modulation

The following is a review of the principal natural ingredients studied in the peer-reviewed scientific literature for their capacity to modulate cytokine production or activity. This is not an endorsement of these ingredients as equivalent to pharmaceutical cytokine therapies; it represents the state of scientific evidence as published in indexed journals.

7.1 Curcumin (Curcuma longa)

Curcumin is the main polyphenol in turmeric. It is a highly potent antimicrobial agent with antioxidant, anti-inflammatory, anticancer, and antidiabetic properties. Curcumin has been shown to decrease the secretion of various critical pro-inflammatory cytokines including IL-1, IL-2, IL-6, IL-8, IL-10, IL-11, IL-12, IL-17, tumor necrosis factor alpha (TNF-α), and interferon-gamma (INF-γ), and chemokines such as monocyte chemoattractant protein 1, macrophage inflammatory protein 1α, nuclear factor kappa-light-chain enhancer of activated B cells (NFĸB), cyclooxygenase, plasminogen activator inhibitor-1, and caspase-3.

Curcumin and its chemical analogues were shown to inhibit NF-κB activated by several different inflammatory stimuli. Moreover, curcumin and analogues reduced the expression of inflammatory cytokines including TNF and IL-1, and adhesion molecules like intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in human cell systems.

Clinical Evidence (Curcumin — Nano-Curcumin in COVID-19): In Iran, a randomized, double-blind, placebo-controlled study was carried out on COVID-19 patients from the Imam Reza Hospital of Tabriz University of Medical Sciences. This study aimed to evaluate the efficacy of nano-curcumin (dose: 160 mg in four 40 mg capsules daily for 14 days) in modulating the levels of inflammatory cytokines IL-1β, IL-6, TNFα, and IL-18 in 40 patients.

Clinical Evidence (Curcumin + Quercetin): An exploratory, pragmatic, open-label, randomized controlled clinical trial was conducted at the Department of Pathology, Liaquat University of Medical and Health Sciences, Jamshoro, Pakistan. The study compared the treatment effect of an oral curcumin-quercetin (CUR-QUE) supplement plus standard of care vs. standard of care alone in early-stage, mild to moderately symptomatic COVID-19 outpatients. Patients were randomized in a 1:1 ratio to CUR-QUE (n = 25) and control (n = 25) treatment groups. The CUR-QUE supplementation consisted of a daily intake of 168 mg curcumin and 260 mg quercetin, as two soft capsules, to be taken twice a day at home for 14 days. After one week of treatment, most of the patients in the CUR-QUE group showed expedited clearance of the viral infection (72.0% vs. 24.0% in the control group tested negative for SARS-CoV-2, p = 0.0002). COVID-19-associated acute symptoms were also more quickly resolved in the CUR-QUE treated patients. The CUR-QUE supplementation therapy was well-tolerated by all 25 patients and no treatment-emergent effects or serious adverse events were reported.

Several other clinical trials in hospitalized COVID-19 patients have revealed the immunomodulatory (anti-inflammatory) effects of curcumin therapy, including reduction in the serum levels of IL-1β, IL-6, INF-γ, TNF-α, IL-17, IL-10, IL-35, and TGF-β; reduction in the expression levels of IL-1β and IL-6; as well as upregulation of the frequency of regulatory T cells, reduction in the number of Th17 cells, and Th17 cell-related cytokines levels.

Evidence strength: The majority of mechanistic data for curcumin are from in vitro and animal models. Human clinical evidence is preliminary, with most trials being small, open-label, or limited in scope. Bioavailability of standard curcumin is known to be low; nano-formulations and combination supplements have been used in some trials to address this.

7.2 Quercetin

Quercetin (2-(3,4-dihydroxyphenyl)-3,5,7-trihydroxychromen-4-one) is a polyphenolic flavonoid found in abundance in many plants including broccoli, red onions, eggplant, potatoes, and green leafy vegetables including celery and lettuce; fruits including apples, citrus fruits, red grapes, and tomatoes; and berries including cranberries and raspberries.

Quercetin exhibits diverse anti-inflammatory mechanisms, including the inhibition of lipid peroxidation, pro-inflammatory mediators such as lipoxygenase and phospholipase A2, and the NLRP3 inflammasome-mediated IL-1β production, and diverse proinflammatory cytokines such as IL-1β, IL-6, IFN-γ, and TNF-α. Quercetin has an immunosuppressive effect; this molecule inhibits cytokine production and induces suppression of NLRP3 inflammatory activation. Moreover, the simultaneous administration of quercetin induces immunomodulatory regulation and enhances the antiviral response.

The possible adjuvant effect of quercetin has been investigated in several clinical trials in mild to moderately symptomatic COVID-19 patients, and have revealed beneficial effects including speedy viral clearance, early resolution of COVID-19-associated acute symptoms, and improvement in the serum levels of inflammatory biomarkers such as CRP, LDH, and alkaline phosphatase (ALP).

Evidence strength: Quercetin has a growing body of clinical and preclinical data for anti-inflammatory cytokine modulation, but as with curcumin, the majority of high-quality evidence derives from infectious disease contexts and trials with methodological limitations (open-label design, small sample sizes). Mechanistic in vitro data is strong; human clinical evidence for non-infectious inflammatory conditions remains preliminary.

7.3 Resveratrol

Resveratrol is found in Vitis vinifera, Vaccinium myrtillus, and Vaccinium macrocarpon. It significantly reduced the levels of inflammatory cytokines such as TNF-α, IL-2, MCP-1, IFN-γ, and IL-6 in murine models. Interestingly, the levels of TGF-β increased after resveratrol treatment.

Resveratrol modulates NF-κB/JNK/MAPK signaling, SIRT1 activation, and microglial cytokine release, offering neuroinflammatory and anti-amyloid benefits — though clinical outcomes remain mixed and oral bioavailability is low (~0.5%), prompting exploration of improved formulations.

Despite a large number of in vitro and in vivo studies showing the promissory pharmacological potential of resveratrol, so far there is no real evidence of its effectiveness in clinical human studies.

Evidence strength: Predominantly preclinical. Clinical translation is limited by extremely poor oral bioavailability (~0.5%) and inconsistent human trial outcomes. Most human studies have used various formulations and dosages, limiting comparability.

7.4 Epigallocatechin Gallate (EGCG) — Green Tea Extract

EGCG is the principal bioactive catechin from Camellia sinensis (green tea). In vitro studies show that EGCG markedly suppresses the expression of inflammatory cytokines such as TNF-α, IL-6, IL-8, and IL-1β. In the supplement marketplace, EGCG is frequently combined with other cytokine-modulating ingredients. One commercially available formulation contains EGCG from green tea extract (leaf) at 300 mg per capsule, combined with mung bean extract (coat) at 240 mg providing 24 mg vitexin and 24 mg isovitexin.

Evidence strength: In vitro and animal model data are substantial. Robust human clinical trials examining EGCG's effect specifically on cytokine levels are limited in number and scope; the evidence for its isolated use as a cytokine modulator in humans is preliminary.

7.5 Mung Bean Extract (Vigna radiata)

Mung bean seed coat extract, rich in the flavone glycosides vitexin and isovitexin, has been studied for its potential to inhibit inflammatory cytokines like HMGB1 (high-mobility group box 1 protein). It is most commonly encountered in commercial cytokine-support supplements combined with EGCG. The evidence base for isolated mung bean extract as a cytokine modulator in humans is preliminary and largely derived from in vitro and mechanistic data.

7.6 Flavonoids: Kaempferol, Fisetin, Rutin, Myricetin, Luteolin

Several flavonols, including kaempferol, fisetin, rutin, and myricetin, can inhibit cytokine expression and synthesis. Key polyphenols like quercetin and luteolin, found in plants such as Achyrocline satureioides and Mangifera indica, demonstrate the downregulation of NF-κB and inhibition of pro-inflammatory cytokines.

Evidence strength: Data are primarily from in vitro and preclinical animal models. Human clinical evidence for these individual flavonoids as standalone cytokine modulators is sparse and preliminary.

7.7 Omega-3 Fatty Acids

Using specific nutrients such as omega-3 fatty acids and antioxidant vitamins in extraordinary doses modulates the host immune response and ameliorates the cytokine storm associated with viral diseases. Omega-3 fatty acids (EPA and DHA) are among the most well-documented dietary supplements for influencing cytokine production, largely through modulation of arachidonic acid metabolism and the NF-κB signaling pathway.

Evidence strength: Omega-3 fatty acids have a comparatively stronger clinical evidence base than many plant polyphenols for modulating inflammatory markers, including cytokines. However, studies specifically focused on cytokine storm modulation are largely from acute infection contexts and require further investigation.

7.8 Colostrum- and Egg-Based Peptides

Immune protection associated with consuming colostrum-based peptides has been studied in the context of bacterial and viral insults. A double-blind, randomized, placebo-controlled, cross-over pilot study involved healthy participants attending two clinic visits, with blood draws performed pre-consumption and at 1, 2, and 24 hours after consuming a blend of bovine colostrum- and hen's egg-based low-molecular-weight peptides (CELMPs) versus a placebo. The consumption of CELMPs was associated with rapid changes to blood levels of selected cytokines and chemokines. Specifically, the reduced levels of the pro-inflammatory cytokines IL-6, IL-13, and TNF-α suggest an anti-inflammatory effect. The effects were mild and within the spectrum of normal daily changes in the immune system that occur during the circadian cycle.

Evidence strength: Preliminary. This is a small feasibility study. Results need replication in larger, longer-duration controlled trials before conclusions can be drawn about clinical significance.

7.9 Antioxidant Nutrient Combinations

Modulation of cytokine production using immunonutrition is a relatively novel concept to improve outcomes among patients, and is now hypothesized to help manage clinical inflammatory states; however, clinical evidence is still limited. A prospective, double-blinded, randomized parallel-controlled interventional clinical trial investigated the effect of antioxidant supplements on inflammatory cytokines and disease progression in non-critically ill patients. A total of 87 hospitalized COVID-19 patients were randomized using computer-generated randomization into the supplement group (n = 18) and the placebo group (n = 16) for 10 days. Levels of alkaline phosphatase, IL-6, TNF-α, and MCP-1 were significantly lower in the supplement group. In conclusion, antioxidant oral supplementation significantly reduced the cytokine storm and led to partial improvements in clinical parameters among patients with non-critical COVID-19.

Evidence strength: This trial, like others of its kind, used a combination supplement, making it impossible to attribute effects to any single ingredient. Sample sizes were small, and the context (acute infectious disease) limits generalizability to chronic inflammatory conditions.

8. Dosage Forms and Reported Dosages

Because cytokines themselves are not orally administered dietary supplements under normal circumstances, dosage data in this section refers to natural ingredients studied for cytokine modulation and to pharmaceutical cytokine preparations:

Nano-curcumin (clinical trial): 160 mg daily (administered as four 40 mg capsules) for 14 days, as used in a randomized, double-blind, placebo-controlled COVID-19 trial.
Curcumin + Quercetin (clinical trial): 168 mg curcumin and 260 mg quercetin daily as two soft capsules taken twice per day for 14 days.
EGCG (commercial supplement): 300 mg EGCG from green tea extract per capsule, with a suggested use of one capsule daily.
Mung bean extract (commercial supplement): 240 mg mung bean seed coat extract providing 24 mg vitexin and 24 mg isovitexin per capsule.
Pharmaceutical interferon beta (clinical use): Interferon beta-1a at 30 µg given intramuscularly once per week, and interferon beta-1b at 44 µg subcutaneously every other day, have been compared in clinical trials of multiple sclerosis.

These dosages are reported as stated in published sources and should not be extrapolated beyond their original study contexts.

9. Safety Considerations and Known Adverse Effects

9.1 Exogenous Pharmaceutical Cytokines

Underlying each adverse event profile of therapeutic cytokines is their pleiotropism, potency, and capacity to release other cytokines producing cytokine "cocktails." Side effects, some serious, occur despite cytokines being endogenous proteins, and this therefore demands caution in attempts to introduce individual members into the clinic. This caution is reflected in the relatively small number of cytokines currently approved by regulatory agencies, and by the fact that 14 of the FDA-approved preparations carry warnings, with 10 being black box warnings.

A large body of clinical experience on the adverse consequences of cytokine administration has accumulated. Side-effects reported after the therapeutic use of cytokines has provided evidence that activation of the immune response may sometimes have deleterious consequences. Several effects appeared as a direct consequence of the immune activation induced by cytokines, including flu-like reactions and vascular leak syndrome. Cytokine-induced exacerbation of underlying diseases or immune dysregulation were other complications of growing concern.

A major difficulty in using exogenous IL-2 and other exogenous cytokines in vivo is their high toxicity. Side effects are of considerable magnitude, particularly cardiac symptoms and dysfunctions, septic shock, and fever. This requires intensive care for adverse effects remediation or control, and may also lead to discontinuation of treatment.

A flu-like illness is the most commonly occurring adverse event following administration of the interferon beta proteins. The questions of the production of neutralizing antibodies to interferon beta and whether they reduce the therapeutic effectiveness in treated patients, especially in the treatment of multiple sclerosis, are important ones. Such antibodies are found in about a quarter of patients treated with subcutaneously administered interferon beta-1b, and the consensus is that they neutralize or reduce the cytokine's activity.

9.2 Natural Cytokine-Modulating Ingredients

In the curcumin-quercetin clinical trial, the CUR-QUE supplementation therapy was well-tolerated by all 25 patients and no treatment-emergent effects or serious adverse events were reported. However, this was a small, short-duration study and cannot establish a comprehensive safety profile.

Some synthetic drugs, including IFN-γ and IL-1 blockers, have been found to be clinically applicable in treating cytokine storm-related diseases. Although these drugs do have certain clinical effects, they also have various side effects, such as thrombocytopenia and abnormal liver enzyme levels. In recent years, numerous studies have shown that natural products exhibit excellent anti-inflammatory biological activity and have fewer reported side effects.

Controversy has been raised about scaffold promiscuity rather than the real polypharmacological effect of polyphenols like resveratrol. Some molecular docking and dynamic studies have shown that resveratrol displays similar binding modes and target interactions with various proteins; thus, special precaution is required concerning the possible off-target effects.

9.3 Key Safety Principles

The vital role of the immune system in many pathologies makes cytokines promising therapeutics for many disease states. Nevertheless, the dual role of cytokines — essential for defense yet potentially injurious when dysregulated — means that any attempt to pharmacologically elevate or suppress cytokine levels carries inherent complexity. In the context of immunoregulation and autoimmune diseases, cytokines can play either a pro-inflammatory or anti-inflammatory role, mediate a particular T and B cell response, or drive a disease process. Interventions designed to suppress cytokine activity (e.g., to address chronic inflammation) could potentially interfere with the body's normal immune surveillance; conversely, attempts to stimulate cytokine production could exacerbate pre-existing autoimmune or inflammatory conditions.

10. Current State of Evidence: Summary Assessment

Currently, no clinical therapeutic drugs are available with a significant effect and minimal side effects for cytokine storm. Given the pathogenesis of cytokine storm, natural products have become important resources for bioactive agents in the discovery of anti-cytokine storm drugs. Research has aimed to provide guidance for preventing and treating cytokine storm-related diseases by reviewing the natural products identified to inhibit cytokine storm.

Plant extracts and their bioactive ingredients are promising candidates for further research on their safety and effectiveness in preventing cytokine storm symptoms in SARS-CoV-2 patients. Despite the many difficulties in developing bioactive products into COVID-19 drugs, there are increasing efforts to develop antiviral agents from bioactive products in clinical studies.

The overall evidence can be summarized as follows: mechanistic (in vitro and animal model) data for polyphenols such as curcumin, quercetin, resveratrol, EGCG, and related flavonoids is substantial and consistently suggests cytokine-modulating activity. Human clinical evidence, while growing, remains largely preliminary, limited in sample size, frequently conducted in the context of acute infectious disease, and often employing combination formulations that preclude attribution of effects to single ingredients. Rigorous, large-scale, placebo-controlled randomized trials specifically designed to test cytokine endpoints in diverse populations are still needed for most natural cytokine-modulating ingredients.