CD86 is critical for autoantibody and GC formation in BXD2 mice. Spleens from BXD2 and BXD2-Cd86−/− mice (10-mo-old) were harvested. A, Spleen weight and the total cell count, as determined by a hemocytometer, between BXD2, and BXD2-Cd86−/− mice are shown. B, Titers (O.D. absorbance units) of serum autoantibodies to histone, BiP, and DNA from B6, BXD2, and BXD2-Cd86−/− mice. C, Representative (1 of N=6) histological analysis of spleen tissue sections from BXD2 and BXD2-Cd86−/− immunohistochemically stained as described in Materials and Methods with anti-IgG antibody at 10× and 20× objective lens magnifications. D, Left: Flow cytometry analysis of splenic GC B cells (Fas+PNA+, gated on CD19+ B cells first) from BXD2 and BXD2-Cd86−/− mice with indicated percentages of Fas+PNA+ cells. Right: The corresponding representative (1 of N=6) histological analysis of spleen sections from BXD2 and BXD2-Cd86−/− mice at 20× and 40× objective lens magnifications. All results are shown as mean ± SEM (** p<0.01, ***p<0.001 between BXD2 vs BXD2-Cd86−/−, N=6).