Colostrum is a highly-concentrated source of immune and growth factors produced from mammary glands shortly after giving birth. Pure Encapsulations Colostrum is derived from BSE-, hormone-, pesticide- and antibiotic-free USDA certified dairy farms in the U.S. It is collected after the first 24 hours, defatted and standardized to contain 40% IgG. Colostrum contains immunoglobulins G (IgG), A (IgA), E (IgE), D (IgD), and M (IgM). Each has a specific role in immune health. IgG is naturally found in the highest concentration. Other naturally occurring immune support compounds include lactoferrin, proline-rich polypeptide (PRP), lymphokines, interferons, interleukins, oligosaccharides, lysozymes, insulin growth factors (IGF-1 and IGF-2) and transforming growth factors (TGF-A and TGF-B).*