Expression of MHC II, B-cell markers, and plasma cell markers in DLBCL. Chromogenic IHC was performed as described in “Chromogenic IHC” to visualize proteins as marked. Original magnification ×40. The full range of expression (intensity and percentage of positive cells) varied for each protein; images selected show the upper range of expression for that marker. (A) MHCII marker HLA-DR. (B) B-cell marker CD20, and (C) plasma-cell markers CD138, MUMI, PRDM1/Blimp1, XBP1s. Inset: positive staining for CD138 in tonsil control.