Circulating polysaccharide specific B cells in the elderly display a dominant switched memory response to pneumococcal vaccination

Sumbmitted to Blood November 2, 2012

Department of Medicine, University of Toledo, Toledo, OH 43614, USA.
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 these cells as CD27+IgM+ B cells, in healthy young volunteers. However the PPS responding B cell population has not yet been identified in high risk populations, such as the elderly. Previous studies have shown that the elderly have a lower percentage of IgM memory B cells compared to healthy young adults. In this study we directly characterized the phenotype of PPS-specific B cells pre- and post-vaccination with the 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, post-vaccination IgM concentrations were not significantly increased in this population and the opsonophagocytic response was decreased compared to young adults. These findings identify a significant shift in the phenotype of responding B cell population in response to PPV with age.