Figure 7.

CMF-mediated suppression of IL-2 production by CD3-/CD28-activated CD45RA⁺ CD4⁺ T cells is reversed by blockade of PD-L1 or PD-L2. CD45RA+CD4+ T helper cells (Naïve T cells) were preactivated with anti-CD3/anti-CD28 mAbs bearing beads (Activ T cells). (A) Activated T cells were co-cultured with primary culture of CMFs in the presence/absence of anti-human PD-L1 (clone M1H1) or anit-PD-L2 (clone M1H18) blocking mAbs. IL-2 production was measured in 48-hour culture supernatant using a standard IL-2 specific ELISA kit (Pharmingen). Values were expressed in ng/mL and represent the mean ± standard error (SE) of triplicate cultures of T cells isolated from one donor. A representative experiment is shown (n=4 donors, two experiment replicates each). *p < 0.05. (B) Activated T cells were co-cultured with primary culture of CMFs in the presence/absence of different concentrations of human recombinant IL-2. T cell proliferation was measured 72-hour after co-culture by using [3H]-thymidine incorporation (c.p.m.). Values represent the mean counts per minute (c.p.m.) ± standard error (SE) of triplicate cultures of T cells isolated from four donor, *p < 0.05.