Rheumatoid arthritis (RA) molecular phenotypes reflect cellular and biological differences. (A) Immunohistochemical detection of T cells (CD3) and B cells (CD20) in synovial tissue sections. Columns correspond to representative sections for each of the RA molecular phenotypes designated by color-coordinated bars on top. Scales on images refer to a length of 500 microns. (B) Fluorescence activated cell-sorting analysis of fresh synovial tissue samples. Cells were stained with CD3- and CD20- gated by forward and side-scatter lymphocyte parameters and fluorescent intensities plotted in a scatter-plot with T cells (CD3) on the y-axis and B cells (CD20) on the x-axis (top panel). Contour-plots from the same patients above showing macrophages (CD45+, lymphocyte-gate exclusion) along the y-axis and fibroblasts (CD90) along the x-axis (bottom panel). Samples are arranged left to right according to their phenotype membership as in panel A. (C) Bar plots of the percentages of patient synovial tissues that contained non-aggregated (Agg-) or aggregated (Agg+) cellular infiltration as determined by immunohistological assessment of CD3- and CD20-positive cells.