Reduced cell-surface expression of MHC class II in C3^-/-macrophages. (A-B) Thioglycollate-elicited macrophages were prepared from C3^+/+ (n = 6) and C3^-/- (n = 6) mice. Cells from each mouse were then stained for surface molecule MHC class II using PE-conjugated anti-mouse Ig or isotype control Ig. (A) Representative histogram plots for C3^+/+ and C3^-/- peritoneal macrophages. The control peak (dashed line) corresponds to staining cells with the isotype control antibody. The detection peak (solid line) shows surface binding of specific antibody. (B) Expression levels (mean fluorescence intensities, MFI) of MHC class II on macrophages. Data were analyzed by Student t test. (C) C3^+/+ and C3^-/- peritoneal macrophages prepared from 4 mice in each group were pooled and used for RNA extraction and cDNA synthesis and subsequently for semiquantitative PCR. A typical agarose gel shows PCR products for MHC class II, Cd40, Icam1, B7.2, and GAPDH (internal control). Results are representative of 3 independent experiments.