A. B6 recipients of BALB/c heart allografts were treated with mATG (d. 0, 4) with or without additional CD4 T cell depletion (d. −3, −2, −1). T cell recovery was monitored in peripheral blood and in the spleen. B. Spleen CD8 T cell reconstitution in B6.CD4−/− mice transplanted with BALB/c heart allografts and treated with mATG. C. Kaplan-Meier plot represents heart allograft survival in recipients depicted in (A). D. Numbers of graft infiltrating CD8 T cells on day 10 posttransplant. Graphs represent mean ±SD in two independent experiments with total of 6-9 animals per group. E. Recipient spleen cells were tested in a recall IFNγ ELISPOT assay against donor BALB/c or third party SJL stimulator cells. The results are presented as frequencies of donor-reactive IFNγ secreting cells in individual recipients and are representative of two independent experiments with total N = 6-9 mice per group. F-G. B6 recipients of BALB/c heart allografts were treated with depleting anti-mouse CD8 mAb (d. −3, −2, −1) with or without CD4 T cell depletion and evaluated for CD8 T cell recovery (F) and heart allograft survival (G). Data are presented as mean ±SD, N = 6-9 animals per group. *P < 0.05; **P < 0.01; ***P < 0.001.