CD28 and Stroke: Moreover, five stroke patients appeared to have increased baseline CD137 expression (CD4+: 6.7 ± 2.0%; CD4+CD28–: 3.8 ± 0.6%) compared with the rest of the population, but all of these patients demonstrated a continuous decrease in CD137 expression on CD4+ and CD4+CD28– T cells at 3 and 14 days posttreatment, while the lymphocytes presented irregular variations (Figure2).