CD28 and B-cell chronic lymphocytic leukemia: The mean percentage of CD3+/CD8+/CD28+ cells was also significantly lower in B-CLL patients than in controls before stimulation (P=0.005), and after 24 h (P=0.001), 48 h (P=0.001), 72 h (P=0.01) and 96 h (P=0.01) of stimulation (Table 1).