Antibody-forming cells in human colostrum after oral immunisation

IT has been suggested that feeding infants with human milk reduces the incidence of gastrointestinal infections¹. Although macrophages, lymphocytes and antibodies in the milk are probably important in this protection^2,3, the mechanism for the development of specific immunity to enteric pathogens is not known. Human colostral cells synthesise IgA (ref. 4), and we have used the haemolysis-in-gel technique to demonstrate that human colostrum contains numerous cells which produce IgA antibodies against the O antigens of commonly encountered Escherichia coli bacteria⁵. This suggested that the sensitised lymphocytes had either undergone antigen-induced clonal proliferation within the mammary gland or had homed to that organ from another site after becoming sensitised. Because of reports that gastrointestinal immunisation of germ-free mice led to local⁶ and systemic ⁷ production of IgA antibodies, and that cells from Peyer's patches effectively repopulate the ileum of lethally-irradiated rabbits with IgA-producing cells⁸, we have examined the effect of gastrointestinal immunisation on the development of antibody-producing cells in colostrum of humans. We found that oral administration of a non-pathogenic strain of E. coli led to the rapid appearance of colostral cells producing antibodies against the O antigen of the organism.