ANTIBODIES TO <i>ESCHERICHIA COLI</i> O ANTIGENS AND THE IN‐VITRO BACTERIOSTATIC PROPERTIES OF HUMAN MILK AND ITS IgA

Abstract

Only a very small part of the iron-reversed bacteriostatic activity of milk against Escherichia coli, demonstrable in vitro, is due to its anti-O antibody. Most of its growth-inhibitory activity is due to another lactoferrin-dependent, non-specific system. IgA prepared from milk is bacteriostatic for E. coli in the presence of lactoferrin, if it contains O-antibody for the indicator strain and if the strain is susceptible. Susceptibility depends to some extent on virulence, since those inhibited by IgA antibody to their own O-antigens were enteropathogenic or enterotoxigenic, whereas the growth of commensal strains was inhibited only slightly or not at all.