Source and protective function of coproantibodies in intestinal disease

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Abstract
This paper describes studies of the mechanisms by which intestinal antibody may be delivered to the lumen of the intestine. The results indicate that in all animals studied (conventional mice, conventionalized mice, and germfree mice), antibody may appear in the intestine as a result of local synthesis or may be derived from serum antibody. Serum antibody was degraded in the intestine of all types of mice studied, but degradation in germfree mice was so rapid that no serum antibody was detectable in the intestine. The presence, and probably the quality, of intestinal flora was therefore shown to affect the host by a new mechanism: the sparing of intestinal antibody. High antibody titers in the intestine of orally vaccinated germfree mice were due to secretory IgA antibodies that appeared to be more resistant to intestinal degradation than the IgG and IgM fractions derived from the serum. Purified intestinal IgA antibody was shown to protect in vivo isolated intestinal loops of mice against experimental cholera. The implications of these findings for the problems of prophylactic immunity to bacterial enteric pathogens and of immunological control of normal enteric bacterial flora were disscussed.