The human immunomodulatory CD25+ B cell population belongs to the memory B cell pool

Abstract

We have shown that human CD20+25+ B cells display immunomodulatory properties. The aim of this study was to investigate if CD25+ B cells are found within the CD27 memory B cell population, and to analyse pattern of their cytokine production. B cells isolated from healthy subjects, rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) patients were analysed regarding the frequency of CD25+ B cells within certain B cell subsets. Purified CD25+ B cells from healthy subject were used in vitro to evaluate their production of immunomodulatory cytokines. In healthy subjects the majority (60%) of memory B cells (CD20 +27+) also co-expressed CD25 while only 10-20% of the naïve B cells (CD20+27-) and plasmablasts (CD20-27+) expressed CD25. In RA and SLE patients, we found that 51% and 48%, respectively, co-expressed CD25 in the memory population, whereas only 11% and 9% co-expressed CD25 in the naïve B cell population. Phenotypic analysis of the CD20+25+27+ and CD20 +25+27- cells using CD10, CD24, CD38, CD45, CD71, CD80, CD86, CD95, CD138, BAFF-R, TACI, IgA, IgD, IgG and IgM showed that CD20+25+27+ B cells preferentially represent highly activated, Ig class switched memory B cells. Cytokine profile analysis showed that CD25+ B cells secreted significantly higher levels of IL-10 versus CD25- B cells. In contrast, TGF-β1 secretion was similar between the CD25+ and CD25- sub-populations. In conclusion, CD20+25+ B cells constitute a unique subpopulation preferentially occurring among CD20+27+ memory B cells. We suggest that CD25 can be used as a marker for a memory B cell subset. © 2007 The Authors.