Background: Data on the influence of immunosuppressive drugs on the generation and functions of the B cell subpopulations including B-1a, B1b, and conventional B2 are limited. B1 cells are important cell population producing natural antibodies and involved in antibacterial humoral responses. Among them B1a subset expresses the pan-T cell surface glycoprotein CD5. This molecule is known to modulate lymphocyte activation and differentiation processes. Compared to B2 cells, B1a are long-lived, non-circulating, with reduced BCR affinity.
Material/Methods: The aim of this study was to compare the effects of two
commonly used immunosuppressive drugs, i.e. cyclosporine A (a calcineurine inhibitor) and rapamycin (a cell division inhibitor), on the induction of the B cell subpopulations. Mononuclear cells were obtained from the whole peripheral blood of healthy blood donors. PBMCs were cultured for five days in the presence or absence of either drug. Then the percentages of CD19, CD11b, and CD5 positive cells on PWM-activated and non-activated cells were determined using appropriate monoclonal antibodies. Flow cytometry was performed with a FACSCalibur (BD Biosciences) and data were analyzed using Cell Quest software.
Results: Although both investigated drugs decreased the percentages of B-1a and B1b cells, the difference was statistically significant only in the B-1a subpopulation. On the other hand, neither drug affected the percentage of B2 cells.
Conclusions: The present study is preliminary and we intend to pursue this
line of research by evaluating the influence of immunosuppressive drugs on the functions of the major B cell subpopulations, especially their capability to produce antibodies.

Keywords: Immunosuppression