Statin treatment inhibits the antigen-presenting function of CD40-activated B cells. (A) Purified B cells were activated through CD40 in the presence of simvastatin (0.1, 1, or 10 μM) or vehicle as a control (Contr). Addition of simvastatin to the culture medium prevented activation and homotypic adhesion. Photographs were taken at 100× magnification using a TELEVAL 31 microscope (Carl Zeiss, Jena, Germany fitted with a Canon EOS 350D digital camera. (B) The surface expression of MHC class II and the costimulatory molecules CD80 and CD86 was reduced in a dose-dependent fashion. Expression levels are expressed relative to vehicle-treated controls (n = 4). (C) The immunostimulatory function of CD40-activated B cells was assessed in a mixed lymphocyte reaction (MLR) with carboxyfluorescein diacetate succinimidyl ester (CFSE)–labeled CD4⁺ T cells as responders and CD40-activated B cells, which have been treated with vehicle or 1 μM simvastatin, as stimulators. FACS plots representative of 4 separate experiments are shown. (D) CFSE-labeled CD4⁺ T cells (n = 4) were stimulated with CD3/CD28-coated beads at a ratio of 1:1. Addition of simvastatin at the indicated concentrations interfered with the T cell proliferation. Error bars in panels B and D represent SD.