Figure 3.

CTLA-4 is expressed constitutively on CD25⁺CD45RB^low CD4⁺ cells. (a–c) CTLA-4 staining on permeabilized (a) CD45RB^highCD4⁺, (b) CD25⁺CD45RB^lowCD4⁺, and (c) CD25⁻CD45RB^lowCD4⁺ splenocytes. SSC, side scatter. (d–f) CTLA-4 expression on the progeny of (e) CD25⁺CD45RB^lowCD4⁺ and (d and f) CD45RB^highCD4⁺ cells after transfer into immunodeficient mice. C57BL/6 recombination activating gene (RAG)2^−/− mice received CD45RB^highCD4⁺ cells from C57BL/6 mice (CD45.2) (d) alone or (e and f) in combination with 10⁵ CD25⁺CD45RB^lowCD4⁺ cells from C57BL/6.SJL.CD45 congenic mice (CD45.1). 4 wk after transfer, cells from the mesenteric lymph nodes were stained for CTLA-4 and congenic marker expression. Results are representative of four mice (CD45RB^high alone) and seven mice (CD45RB^high plus CD25⁺) from two independent experiments.