CD18^−/− T cells have intact activation and expansion in response to alloantigen in vivo. WT or CD18^−/− T cells (CD25⁻CD62L⁺) were labeled with CFSE and then injected intravenously into lethally irradiated BALB/c mice at 5 × 10⁶ cells/mouse. Cell division and expansion were determined 4 days after cell transfer. (A) Mean of percentage donor (H2^b+) CD4 (top panels) and CD8 T cells (bottom panels) are shown in spleens of recipients given WT (left panels) or CD18^−/− (middle panels) T cells. CFSE profiles are shown on gated CD4 and CD8 cells (right panels) from WT (black lines) or CD18^−/− (gray lines) donors. (B) Mean of absolute numbers of CD4 or CD8 cells per spleen in recipients that were given WT (■) or CD18^−/− (▩) donor T cells as shown in panel A. Brackets show SEM from 3 mice each group, and data represent 1 of 2 replicate experiments. (C) WT or CD18^−/− T cells (CD25⁻CD62L⁺) were injected intravenously into lethally irradiated BALB/c mice at 2 × 10⁶ cells/mouse, and cell expansion was determined 19 days after cell transfer. Mean of absolute numbers of CD4 or CD8 cells per spleen was shown in recipients given WT (■) or CD18^−/− (▩) donor T cells. Brackets indicate standard errors of the mean from 3 to 4 mice each group, and data represent 1 of 4 replicate experiments.