Antigens in Immunity

Abstract

When newborn rats were injected intraperitoneally with 1 µg or more of Salmonella adelaide flagellin on the day of birth and thereafter twice per week until adult life, they developed immunologic tolerance to this powerful bacterial antigen. Similarly, a single injection into newborn rats of a larger amount (100 µg) of flagellin induced complete tolerance, though this was not as long-lasting as the tolerant state following multiple injections.Rats rendered tolerant to monomeric flagellin also showed a marked degree of partial tolerance to the particulate antigens, polymerized flagellin and intact flagella.When these particulate antigens were injected repeatedly during the newborn period, it was shown that multiple doses of polymerized flagellin produced nearly complete tolerance; on a weight basis, polymerized flagellin was 10 times less efficient than monomeric flagellin. Only a slight degree of tolerance could be produced by multiple injections of intact flagella.The chief value of the study was twofold: First, it showed that convincing tolerance can be induced toward highly “foreign” microbial antigens. Second, elucidation of the minimum amount of antigen capable of giving complete tolerance has set the stage for a meaningful study of the cellular distribution and persistence of antigen molecules responsible for tolerance induction, using radioactively-labeled flagellin and autoradiography.