CD8⁺CD38^high T cells suppress effector CD4⁺ T cell proliferation.

<p>(A) CFSE-labelled CD4⁺ OTII T cells were used as responder and stimulated with OTII^323–339 peptide in the presence of DCs. Either CD8⁺CD38^high (CD38^high) or CD8⁺CD38⁻ (CD38⁻) T cells were added to the culture at different CD8:CD4 ratios. Histograms show the CFSE dilution of the CD4⁺ OTII T cells after three days of culture (gated on CD4⁺ T cells). Numbers represent the percentage of proliferating cells. Proliferation of CD4⁺ T cells incubated with DC only, or in addition with OTII^323–339 peptide are shown as a negative (neg ctrl) and positive control (pos ctrl), respectively. One of at least four independent experiments is shown. (B) Quantification of CD8⁺ T cell-mediated suppression of CD4⁺ T cell proliferation. Values represent the mean±SEM of four independent experiments. Percentage of suppression was calculated as: proliferation in the positive control-proliferation in the probe/proliferation in the positive control×100. *p<0.05 (Mann-Whitney test). (C) Suppression of human CD4⁺ T cell proliferation by CD8⁺CD38⁺ T cells. Anti-CD3 stimulated proliferation of CD4⁺ T cells (pos ctrl) in addition of CD8⁺38^high or CD8⁺38⁻ T cells, or left unstimulated (neg ctrl) was measured by CFSE dilution after four days of incubation. One out of four independent experiments is shown. (D) Quantification of CD8⁺ T cell-mediated suppression of CD4⁺ T cell proliferation. Values represent percentage of suppression of four independent experiments.