The immune response to pneumococcal polysaccharides 14 and 23F among elderly individuals consists predominantly of switched memory B cells

Abstract

The phenotype of B cells that respond to vaccination with the purified pneumococcal polysaccharide (PPS) has been a topic of debate. We have recently identified the phenotype of cells from healthy young volunteers as CD27(+)IgM(+) B cells. However, the PPS-responding B-cell population has not yet been identified in high-risk populations, such as elderly individuals. Previous studies have shown that elderly individuals have a lower percentage of immunoglobulin M memory B cells than healthy young adults. In this study, we directly characterized the phenotype of PPS-specific B cells before and after vaccination with PPS vaccine (PPV) in elderly adults, using fluorescently labeled PPS14 and PPS23F. In contrast to our observations in healthy young volunteers, the PPS-responding B-cell population consisted primarily of switched memory (CD27(+)IgM(-)) B cells. In concurrence with these findings, postvaccination immunoglobulin M concentrations were not significantly increased in this population, and the opsonophagocytic response was decreased, compared with that in young adults. These findings identify a significant shift in the phenotype of the B-cell population in response to PPV among elderly individuals.

Keywords: 23F; B cell; CD27; Pneumococcus; Streptococcus pneumoniae; elderly; flow cytometry; human; polysaccharide; vaccine.

Figure 1.

Pre- and postimmunization pneumococcal polysaccharide (PPS)–selected B-cell phenotypes in elderly individuals. The phenotypes of B lymphocytes that respond to vaccination with PPS vaccine were determined by flow cytometry. Before and 7 days after vaccination, circulating peripheral blood mononuclear cells were isolated and labeled fluorescently with different anti-surface marker antibodies. The phenotype of unselected and PPS14- and PPS23F-selected B cells were compared in elderly individuals. In each sample, 100 000 events were recorded. Abbreviation: IgM, immunoglobulin M

Figure 2.

Pneumococcal polysaccharide (PPS)–labeled B-cell phenotypes in elderly individuals, compared with young adults. The phenotypes of B lymphocytes that respond to vaccination with PPS vaccine were determined by flow cytometry. Before vaccination and 7 days after vaccination, circulating peripheral blood mononuclear cells were isolated and labeled fluorescently with different anti-surface marker Abs. The phenotype of pre- and postvaccination PPS14-selected (A) and PPS23F-selected (B) B cells was compared in young and elderly individuals. In each sample, 100 000 events were recorded. Abbreviation: IgM, immunoglobulin M.