Transfer Factor is a term used for small immune messenger molecules derived from colostrum or egg yolk. It has been studied for its potential to modulate immune responses. The use of Transfer Factor to support the bronchial system (i.e., respiratory health) is based on its purported ability to enhance immune defenses, which may be beneficial in respiratory tract infections or in supporting overall respiratory health.

Scientific evidence for Transfer Factor in supporting the bronchial system is limited and primarily consists of small clinical trials, case reports, and in vitro studies. Some early studies from the 1970s and 1980s investigated Transfer Factor's ability to reduce the frequency or severity of respiratory infections, especially in immunocompromised individuals or children with recurrent respiratory tract infections. These studies reported modest benefits, but most lacked rigorous controls, were underpowered, and have not been widely replicated.

More recent literature focuses on Transfer Factor’s general immunomodulatory effects, such as enhancing natural killer cell activity and modulating cytokine responses, rather than specific effects on the bronchial system. Systematic reviews and meta-analyses are lacking, and major clinical guidelines do not currently recommend Transfer Factor for respiratory or bronchial health.

In summary, while there is some limited scientific evidence suggesting Transfer Factor may support immune function and, by extension, respiratory health, robust clinical validation for bronchial support specifically is lacking.