Figure 2.

A pronounced T cell immunostimulatory effect is detected very early in polymorphonuclear neutrophil granulocytes supernatants (PMN-SN), while arginase-mediated inhibition of T cell proliferation needs much longer PMN-SN incubation time. Human T cells and PMN were isolated from whole blood of healthy donors. PMN were incubated in cell culture medium for (A) 24 h, (B) 48 h, or (C) 72 h in the presence or absence of the arginase inhibitor nor-NOHA (1 mM; n=4 experiments). (D) PMN were incubated in cell culture medium for only 5 min, 10 min, 15 min, or 30 min. Supernatants from these short incubations were collected and PMN were incubated for another 72 h in fresh medium in the presence or absence of nor-NOHA (1 mM; n=3). (A–D) T cells were stimulated with anti-CD3/anti-CD28-tagged beads and cultured in PMN-SN for 48 h. T cell proliferation was determined by [³H]thymidine incorporation over 16 h and values of control stimulated cells in the presence of arginine were set as 100%. Unless otherwise stated, statistical analysis refers to the control conditions of activated T cells in the presence of L-arginine and nor-NOHA. Statistical calculations were performed with one-way ANOVA and Tukey´s post hoc test (***p < 0.001, *p < 0.05).