Human milk anti-E. coli antibodies: Relationship to maternal parity

Fifty samples of human milk obtained on the third day after delivery were analysed for antibody titers against E. coli antigens, using the passive haemagglutination test (PHA). Antigens were prepared from two "enteropathogenic" E. coli strains (0111:B4 and 0.26:B6) and one "saprophitic" strain (088) by two methods of extraction for each bacterial strain: 1. with water at 100°C, and 2. with veronal buffer, pH 8.4. The milk samples were classified into three groups: after the first parturition [17], after the second parturition [14], and after the third or subsequent parturition [19]. The mean antibody titer was highest in the first group and lowest in the third group. The immunoglobulins in the milk samples, characterized by the radial immunodiffusion test, were found to be IgA and IgM. The concentration of IgA was relatively higher than that of IgM in all the groups; no IgG was detected. The third group showed the lowest concentrations of immunoglobulins. In an attempt to characterize the type of anti-E. coli antibodies, several samples were fractionated on DEAE-cellulose. Using the PHA test, it was possible to demonstrate that only the IgA fraction contained E. coli antibodies. These results suggest that the anti-E. coli antibodies in human milk are mianly of the IgA type and that a decrease of immunoglobulin concentration can be observed after three or more parturitions.