Expression of CTLA-4 and CD25 as regulatory T-cell markers. Analysis of representative Tr clone P8(1) (left), showing CTLA-4 up-regulation when the clone is specifically stimulated with APCs presenting peptide 72H-86L, Rh protein autoantigen, or anti-CD3/CD28 stimulatory antibody. Conversely, CD25 is down-regulated by the clone after specific stimulation with APCs presenting cognate autoantigen in the form of peptide 72H-86L or Rh protein (right) but is up-regulated, as expected, by anti-CD3/CD28 stimulation. Number of IL-10 positive cells are represented in upper right quadrant as a percentage of the total CD4⁺ T-cell poplation. Experimental detail is described in Figure 2.