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
Immunoglobulin A is the most prevalent and is also called "secretory IgA" (sIgA). sIgA is the main immunoglobulin found in mucous secretions, including tears, saliva, sweat, colostrum and secretions from the genitourinary tract, gastrointestinal tract, prostate and respiratory epithelium. It is also found in small amounts in blood. The secretory component of sIgA protects the immunoglobulin from being degraded by proteolytic enzymes, thus sIgA can survive in the harsh gastrointestinal tract environment and provide protection against microbes that multiply in body secretions. sIgA can also inhibit inflammatory effects of other immunoglobulins. IgA is a poor activator of the complement system, and opsonises