Background. Untreated human immunodeficiency virus (HIV) disease leads to abnormalities in all major lymphocyte populations, including CD4⁺ T cells, CD8⁺ T cells, and B cells. However, little is known regarding the effect of antiretroviral therapy (ART)-induced decrease in HIV viremia on B cell numbers and subpopulations.

Methods. We conducted a longitudinal study to evaluate changes in B cell numbers and subpopulations that occur during the course of 12 months of effective ART in a group of individuals with chronic HIV infection.

Results. ART-induced decrease in HIV viremia was associated with a significant increase in B cell counts, similar to increases in CD4⁺ T cell counts yet distinct from the lack of increase in CD8⁺ T cells. The increase in B cell counts was accompanied by a significant decrease in the frequency of apoptosis-prone B cell subpopulations, namely mature activated and immature transitional B cells, which are overrepresented in untreated HIV disease. The increase in B cell counts was reflected by a significant increase in naive and resting memory B cells, both of which represent populations that are essential for generating adequate humoral immunity.

Conclusions. Normalization of B cell counts and subpopulations may help to explain the improvement in humoral immunity reported to occur after an ART-induced decrease in HIV viremia.