Kinetics of surface expression of CD154 in stimulated T lymphocytes (a) CD154 kinetic expression in CD4+ T lymphocytes from patients with rheumatoid arthritis (RA) after stimulation with anti-CD3/anti-CD28, according to CD154 genotype. Peripheral blood mononuclear cells from patients with RA (24CAs group, n = 19; non-24CAs group, n = 16) were stimulated in vitro with anti-CD3/anti-CD28 for 24, 48, 72, and 92 hours. After this, the surface expression of CD154 was measured by flow cytometry. The graph shows the median percentage of CD154 expression in CD4+ T lymphocytes from each group at the indicated times. *P = 0.046, comparing the 24CAs group with the non-24CAs group. (b) Cytometry histograms showing CD154 staining (thick line) compared with non-specific staining (isotype control mAb, thin line) in CD4+ T lymphocytes from representative patients with RA (upper panel, 24CAs; lower panels, non-24CAs), after 24 hours (left panels) and 48 hours (right panels) of stimulation with anti-CD3/anti-CD28. PE, phycoerythrin.