Maturation of regulatory factors influencing magnitude of antibody response to capsular polysaccharide of type III Streptococcus pneumoniae.

Mice of different ages were evaluated for their ability to give a plaque-forming cell response to the capsular polysaccharide of Streptococcus pneumoniae (SSS-III). The response of amplifier and suppressor thymus-derived (T-) cells was also evaluated. The responses to an optimally immunogenic dose of SSS-III for two-and three-week-old mice were only 7% and 14%, respectively, of that produced by adult mice; values comparable to those of adult mice were attained by four weeks of age. Activity of amplifier T-cells, which was minimal at two to four weeks of age, matured slowly and did not reach a maximum until eight to 10 weeks of age. However, activity of suppressor T-cells was found to be fully developed as early as two weeks of age. These findings indicate that the inhibitory effects of suppressor T-cells are predominant in young mice and that such cells may play an active role in determining the ease with which immunological unresponsiveness is induced in neonates.