["An accumulation of late-differentiated CD8+ T-cells together with fewer B-cells and seropositivity for cytomegalovirus (CMV) characterises an 'immune risk profile' associated with mortality in elderly people and represents one of the hallmarks of 'immunosenescence'.", 'While differences in memory T-cell phenotypes between young and old people have been intensively studied, and the role of CMV is well-accepted as a driving force in this regard, the impact of CMV on B-cells, if any, has been relatively neglected thus far.', 'Here, we avail ourselves of blood samples from participants of the Berlin Aging Study II (BASE-II) to compare peripheral blood B-cell differentiation phenotypes of 140 age- and gender-matched CMV-seronegative or -seropositive adults aged between 24 and 85 years using multicolour flow cytometry analysis.', 'We found that the frequencies of naïve B-cells within the CD19+ population were not significantly different in younger and older CMV-seronegative people. This was also true in CMV-seropositive subjects. The frequencies of late-differentiated B-cells were also not different in CMV-negative elderly and young. However, in marked contrast to the T-cell compartment, this was also true for late differentiated B-cells. Within age groups, the most marked differences in the distribution of B-cell phenotypes were between CMV-seronegative and -seropositive subjects, for both genders.'] Does cytomegalovirus Infection Minimally affect the Frequencies of B-Cell Phenotypes in Peripheral Blood of Younger and Older Adults?