Phenotype and function of CD25+CD4+ regulatory T cells from human peripheral blood. (a) CD25+CD4+ T cells are anergic. Purified CD25+ and CD25-CD4+ T cells from the peripheral blood of a healthy individual were stimulated with a monoclonal antibody against CD3, and proliferation was assessed by incorporation of 3H-labeled thymidine into newly synthesized DNA after 96 hours of culture. (b) CD25+CD4+ T cells inhibit the proliferation of autologous peripheral blood mononuclear cells (PBMC). Human PBMC were stimulated with monoclonal antibodies against CD3 in the absence or presence of autologous purified CD25+ or CD25-CD4+ T cells. Proliferation was assessed as described in (a). (c) The regulatory capacity of CD25+CD4+ T cells is inhibited by exogenous IL-2. Human PBMC were stimulated as in (b) in the presence of a non-mitogenic concentration of human IL-2. Proliferation was assessed as in (a). (d) Suppression by CD25+CD4+ T cells is contact-dependent and independent of regulatory cytokines. Human PBMC were stimulated with a monoclonal antibody against CD3 in the presence of autologous CD25+CD4+ T cells and neutralizing monoclonal antibodies against IL-10 (αIL-10) or IL-4 (αIL-4), or separated from CD25+CD4+ T cells by an insert ('transwell'). Proliferation was assessed as described in (a).
Leipe et al. Arthritis Research & Therapy 2005 7:93 doi:10.1186/ar1718