Elderly immune response to a TI-2 antigen: heavy and light chain use and bactericidal activity to Neisseria meningitidis serogroup C polysaccharide.

Previous studies of the elderly immune response to TI-2 antigens failed to correlate specific antibody levels with function and to compare responses with those of young adults. Neisseria meningitidis serogroup C capsular polysaccharide (MCPS) was used as a model TI-2 antigen. Anti-MCPS antibody levels were determined in elderly individuals and correlated with bactericidal activity. The anti-MCPS response in most persons was characterized by predominant IgG usage, with IgG2>IgG1. No light chain or IgA subclass predominated, but some responses showed a particular chain type. Bactericidal activity correlated best with IgG2 levels. Elderly subjects had lower anti-MCPS responses than the young adults did in all chain-specific anti-MCPS levels, and levels declined more rapidly. Bactericidal activity following immunization was significantly lower in the elderly persons. These results suggest the anti-MCPS antibody repertoire in the elderly is likely maintained, and the lower level of function is related to the lower antibody levels.