Anti-Pneumococcal Capsular Polysaccharide Antibody Response and CD5 B Lymphocyte Subsets

ABSTRACTThe role of CD19+CD5+and CD19+CD5−B cell subpopulations in the antibody response to pneumococcal capsular polysaccharides (caps-PSs) is controversial. In the present study, we evaluated the role of human CD19+CD5+and CD19+CD5−cell populations in the serotype-specific antibody response to caps-PS. After vaccination of 5 healthy human adults with Pneumovax (23-valent pneumococcal polysaccharide vaccine [PPV23]), IgG anti-caps-PS serotype 4 antibody-producing cells resided mainly in the CD19+CD5−B cell subset, as assessed by enzyme-linked immunosorbent spot (ELISpot) analysis. Moreover, in a humanized SCID mouse model, CD19+CD5−B cells were more effective than CD19+CD5+cells in producing IgG anti-cap-PS antibodies. Finally, an association was found between the level of IgG anti-caps-PS antibodies and the number of CD19+CD5−B cells in 33 humans vaccinated with PPV23. Taken together, our data suggest that CD5 defines a functionally distinct population of B cells in humans in the anti-caps-PS immune response.