Transmission of maternal antibody prenatally and from milk into serum of neonatal rabbits.

Rabbit dams fed 0.1% BSA for various periods before and during lactation produced anti-BSA of low avidity and IgG isotype in serum and milk. Milk anti-BSA and IgG concentrations were one-third to one-half of those in the serum. At birth, kits had IgG and anti-BSA serum concentrations approximately equal to their dams. Both fell rapidly for the first 10-20 days, levelling off at about 1 mg IgG/ml. Kits born to unimmunized dams and suckled by dams with anti-BSA in the milk showed increasing anti-BSA in serum for the first 12-16 days, falling by 20 days. Foster-suckling on immunized dams beginning at various times after birth showed antibody uptake from birth through 12 days of age. Thus immunoglobulins are among factors absorbed from milk that have potential for regulating the immune responses of rabbit neonates.