[Immunoglobulins A and G in the intestinal secretions of rats in different microbiologic conditions].

Experiments were made with 3 groups of inbred CDF (F344) Crl rats: 30 germ-free, 30 conventional and 18 germ-free animals infected orally with Shigella flexneri 2aN 516. Secretory IgA (S-IgA) was isolated from gut secretion of the conventional rats to obtain rabbit antiserum against it. The levels of S-IgA, IgA and IgG in blood serum and gut secretion were determined. It was shown that gut secretion of the germ-free rats contained no less S-IgA than that from the conventional rats, at the same time IgG was not found in the germ-free rats. After injection of the germ-free rats with Shigella flexneri the content of S-IgA in gut secretion did not rise but there appeared IgG which differed immunochemically from serum IgG2. Within the first week after the injection, gut secretion showed specific antibodies to Shigella flexneri, which was ascertained with the aid of the hemagglutination inhibition test. The titers of antibodies exceeded 1:4096 by day 21. Antibodies in serum appeared much later and in low titers (1:16, 1:32). Therefore, the local immune response was marked to a greater degree than the generalized one. In spite of the presence of specific antibodies in high titers, Shigella flexneri persisted in the hosts, i. e. one could observe a clinically normal bacterial carriage.