Functional capacitiy of T cells isolated from ATXBM PVG rats repopulated with small T-cell numbers and treated with CD28 superagonist or isotype control antibody. (A) Proliferative response to allogeneic (LEW) stimulator cells. (B) Proliferative recall response to KLH (▪ indicates isotype control; ▴, CD28 superagonist). Means and SDs are shown (n = 6). *P < .05; **P < .01. (C) Cytokine production after KLH restimulation.