Figure 4.

T cell proliferation is altered by IL-2 and NOS activity in splenocytes derived from WT and IDO^−/− mice. Splenocytes were isolated from naïve or T. gondii ME49-infected wild-type (WT) and indoleamine 2,3-dioxygenase 1-deficient (IDO^−/−) mice (WT naïve: n = 7; IDO^−/− naïve: n = 5; WT infected: n = 8; IDO^−/− infected: n = 10). Splenic T cell cultures were stimulated with the mitogen concanavalin A (ConA, 1 μg/ml) ex vivo. Supplementation of human interleukin-2 (IL-2, 5 ng/ml) and the nitric oxide synthase (NOS) inhibitor N^G-monomethyl-L-arginine (N^GMMA, 100 μg/ml) was done as indicated (A,B). Lymphocyte proliferation was determined with the ³H-thymidine method. (A). Nitrite accumulation in the supernatant of ex vivo cultured splenocytes was detected using the Griess reaction (B). Data were represented as means of triplicate measurements ± standard error of the mean. The Student's t-test (unpaired, two-tailed) was used to determine statistical differences marked with asterisks (n.s. = not significant; *p ≤ 0.05, **p ≤ 0.001, and ***p ≤ 0.0001).