Transfer factor factors are contraindicated for women who are pregnant or breastfeeding. When human- and bovine-derived transfer factor are generated from blood cells they carry the potential for blood-borne disease such as HIV/AIDS and Hepatitis C. Colostrum is a form of milk produced by the mammary glands of mammals (including humans) in late pregnancy. Colostrum also contains multiple immune modulating molecules, including high antibody levels. Based on studies noting an overlap in the observed in vitro effects between a molecule contained in colostrum called colostrinin and the dialyzable leukocyte extract mentioned above, a hypothesis formed that the two were the same. There
Colostrum on adult gut health in several recent well controlled published studies. Evidence for the beneficial effect of colostrum on extra-gastrointestinal problems is less well developed, due in part to the limited number of randomised double-blind studies published, although a variety of possible uses have been suggested. Dairy cattle are naturally exposed to pathogens and produce immunoglobulins against them. These antibodies are present in the cow’s bloodstream and in the colostrum. These immunoglobulins are specific to many human pathogens, including "Escherichia coli, Cryptosporidium parvum, Shigella flexneri, Salmonella "species", Staphylococcus" species, and rotavirus (which causes diarrhea in infants). Before the development of