Immunity to Salmonella gallinarum during ontogeny of the chicken: IV. Immunocyto-adherence and a cytophilic antibody

Enhanced numbers of immunocyto-adherent (ICA) cells were found in spleens only after two injections of Salmonella gallinarum and then only if the chicken were at least 4 weeks old at the time of the second injection. There was a steady increase in the proportion of ICA cells elicited by a second injection of S. gallinarum during 6–14 weeks of age. As young chickens are quite resistant to infection with this organism by 5 weeks of age, ICA does not appear to be a protective immunological reaction. Increase in spleen cell populations exhibiting ICA were not always correlated with high titres of cytophilic antibody in the circulation of such birds. In fact, a single injection of S. gallinarum elicited high titres of cytophilic antibody in adult serum, when there was no increase in the level of ICA cells. Titres of cytophilic antibody were closely similar to those of agglutinins; however, these antibodies may be separate entities.