Figure 3.

Proliferative response of peripheral blood T cells to ICOS co-stimulation. Peripheral blood T cells isolated from patients with active SLE (n = 14), patients with inactive SLE (n = 16), and normal control individuals (n = 14) were cultured for 72 hours with or without stimulation and pulsed with [³H]thymidine during the last 8 hours. (a) [³H]thymidine incorporation without stimulation. The median value of each group was as follows: active SLE, 78.9 counts/min; inactive SLE, 15.9 counts/min; and normal control individuals, 9.9 counts/min. (b) Inhibition of ICOS co-stimulation by B7RP-1. Peripheral blood T cells from normal control individuals were stimulated with either anti-CD3 mAb plus JTA009 or anti-CD3 mAb plus anti-CD28 mAb in the presence of various concentration of B7RP-1-Fc. Proliferation of peripheral blood T cells with ICOS co-stimulation, but not that with CD28 co-stimulation, was dose dependently inhibited by the addition of B7RP-1-Fc to cell culture medium. (c) [³H]thymidine incorporation with ICOS co-stimulation. The median values in each group for ICOS co-stimulation were as follows: active SLE, 8063 counts/min; inactive SLE, 6050 counts/min; and normal control individuals, 1481 counts/min. Bars indicate median values in each group. *P < 0.05, **P < 0.01, ***P < 0.005 by Mann-Whitney U-test. B7RP, B7-related protein; ICOS, inducible co-stimulator; mAb, monoclonal antibody; NC, normal control; SLE, systemic lupus erythematosus.