Milk immunoglobulins and complement factors

The importance of colostrum for the growth and health of newborn offspring is well known. In bovine colostrum, the antibody (immunoglobulin) complemen t system provides a major antimicrobial effect against a wide range of micr obes and confers passive immunity until the calfs own immune system has mat ured. Bovine serum and lacteal secretions contain three major classes of im munoglobulins: IgG, IgM and IgA. The immunoglobulins are selectively transp orted from the serum into the mammary gland, as a result of which the first colostrum contains very high concentrations of immunoglobulins (40-200 mg/ ml). IgG1 accounts for over 75% of the immunoglobulins in colostral whey, f ollowed by IgM, IgA and IgG2. All these immunoglobulins decrease within a f ew days to a total immunoglobulin concentration of 0.7- 1.0 mg/ml, with IgG 1 representing the major Ig class in milk throughout the lactation period. Together with the antibodies absorbed from colostrum after birth, the compl ement system plays a crucial role in the passive immunisation of the newbor n calf. The occurrence of haemolytic or bactericidal complement activity in bovine colostrum and milk has been demonstrated in several studies. This r eview deals with the characteristics of bovine Igs and the complement syste m to be exploited as potential ingredients for health-promoting functional foods.