CD40LG and digestive system infectious disorder: These maternal milk antibodies include IgA, IgG and IgM isotypes as well as the secretory forms of IgA and IgM.4 Although all three major classes of immunoglobulins are present in human colostrum and milk, only IgA and IgM are locally produced in the human mammary gland.5 These immunoglobulins protect neonates and infants against infection, particularly IgA protects against respiratory tract and gastrointestinal infections.6 IgG may play a protective role in the mucosal immune system and may be the most important immunoglobulin in the lower respiratory tract in the newborn period.