Naïve and memory B cells in the rhesus macaque can be differentiated by surface expression of CD27 and have differential responses to CD40 ligation

The rhesus macaque (RM) model has the potential to be an invaluable tool for studying B cell populations during pathogenic infections, however, to date, there has been no definitive delineation of naïve and memory B cell populations in the RM. This has precluded a rigorous analysis of the generation, persistence and resolution of a pathogen-specific memory B cell response. The present study utilized multiple analyses to demonstrate that CD27 expression on B cells is consistent with a memory phenotype. Compared to CD20+CD27- B cells, CD20+CD27+ B cells were larger in size, and preferentially accumulated at effector sites. Direct sequence analysis revealed that CD20+CD27+ B cells had an increased frequency of point mutations that were consistent with somatic hypermutation and at a functional level, CD40 ligation improved CD20+CD27- but not CD20+CD27+ B cell survival in vitro. These data provide definitive evidence that the naïve and memory B cell populations of the RM can be differentiated using surface expression of CD27.