Recipient CD4⁺ T cells, CD8⁺ T cells, and NK cell-independent proliferation of activated donor T cells by IL-10.

C57BL/6 mice were injected intravenously with 300 μg rat IgG (control IgG), anti-CD4, anti-CD8, or anti-asialo–GM1 mAbs 2 day before they received activated OT-1 T cells, followed by IL-10 administration. Mice were killed 1 week later. Complete depletion of the relevant lymphoid subset was confirmed by CD4, CD8, and NK cell staining monitored by flow cytometry (data not shown). (A) Efficacy of T- or NK-cell depletion was evaluated by anti-CD8 mAb (FITC) and OVA-specific tetramer (PE) staining of spleen cells from treated and healthy mice. The number indicates the percentage of OVA-specific activated T cells (CD8⁺ CD44^hi population). OVA-specific tetramer-staining showed that prior antibody-mediated depletion of CD4⁺ and CD8⁺ T cells did not affect the ability of IL-10 to trigger the increase in numbers of transferred activated OT-1 T cells. (B, C) Functional efficacy (cytotoxicity) by depletion of CD8⁺ T cells or NK cells did not show significant differences; however, depletion of CD4⁺ T cells increased the number of spots for EG.7-OVA (B) and OVA-peptide (C). (Mice with control IgG vs mice with control IgG and IL-10 [P < .0001], and mice with control IgG and IL-10 vs mice with anti-CD4 and IL-10 [P < .005]), determined in ELISPOT assays.