Regulatory Role of T Cells in IgG Antibody Formation and Immune Memory to Type III Pneumococcal Polysaccharide

Abstract

Mice immunized with Type III pneumococcal polysaccharide (S3) produce only IgM antibodies and there is no evidence for immune memory after a second challenge with the antigen. However, when mice undergoing an allogeneic effect are immunized with S3, IgG antibody is produced by some, but not all, strains of mice. Mice also produce IgG antibody specific for S3 when they are immunized twice with a thymus (T) dependent form of antigen, S3 coupled to sheep erythrocytes (S3-SRBC), and these mice develop S3-specific immune memory. Since the allogeneic effect and immunization with S3-SRBC would be expected to result in activation of alloantigen-specific or carrier-specific T cells, the results suggest that T cells play an important regulatory role in IgG antibody formation and immune memory for a presumably T-independent antigen. IgG antibody was also produced when mice were immunized with S3 and treated with anti-lymphocyte serum (ALS). Since ALS presumably removes suppressor T cells it is suggested that S3-specific “helper” T cells may exist but that suppressor cells normally prevent them from being expressed when mice are immunized with S3 alone.