CD4+CD28null T cells are rare in the synovial membrane. Representative immunostaining of one patient, using three-colour immunofluorescence microscopy, to identify CD4+CD28null T cells in the inflamed synovial membrane. The four photographs depict each marker alone or superimposed of the same area of Patient 3 (Table 1): CD3 (blue), CD4 (red) and CD244 (green). Arrows indicate CD4+CD28null (CD3+CD4+CD244+) T cells. Original magnification, ×32. Inserted flow cytometry panel displays the expression CD244 and CD28 on CD3+CD4+ T cells in peripheral blood.