CD8 Tregs suppress Th1- and Th2-associated immunity in vivo. (A-B) C57BL/6 mice were immunized with 400 μg OVA/alum + PBS (OVA alone) or 2.5 × 10⁶ OT-1 Tc1 and Treg cells intraperitoneally. Serum anti-OVA IgG1 (A) and IgE (B) antibodies were monitored by serial bleeding. Antibody titers are shown in arbitrary units. (C-G) Alloantigen-primed CD8 Tregs prevent development of chronic GVHD. Tc1 cells or Tregs were generated in MLRs as in Figure 2D. GVHD was induced by injection of CB6F1 mice with 7 × 10⁷ BALB/c splenocytes, ± Tc1 cells or Tregs (3 × 10⁶). Control F1 mice received PBS only. After 7 weeks spleens were harvested and weighed to assess splenomegaly (C) and engraftment of donor BALB/c cells in each spleen measured by staining for H-2K^b (D). Donor cells lack H-2K^b; the percentage of donor engraftment in CD4 and CD8 populations is indicated. (E) Kidneys harvested at 7 weeks were sectioned and stained with anti–IgG1-FITC before fluorescence microscopy. Deposition of IgG1 immune complexes in glomeruli is indicated by the green fluorescent structures. (F-G) Suppression of autoantibody production (F) and hyper-IgE syndrome (G) by CD8 Treg cells. Mice as in panel C were monitored for anti-DNA IgG2a autoantibodies (F) and total serum IgE (G). Data shown are means ± SEMs from groups of 4 mice (A-C and F-G) or are representative of groups of 4 mice (D-E). Similar data were obtained in a further experiment with groups of 3 mice. *P < .05 when comparing Tregs with the Tc1 control group.