Loss of Cdk5 expression results in fewer donor-derived, cytokine-producing T cells early after HCT. Lethally irradiated B6D2F1 received HCT from either syngeneic (B6D2F1) or allogeneic Cdk5^+/+C (Cdk5 wt) or Cdk5^−/−C (Cdk5 ko) donors as described in Figure 2. HCT recipients were sacrificed and single-cell suspensions were prepared from spleen of mice 3, 7, 14 days posttransplant. Total numbers of donor-derived, CD4⁺ and CD8⁺ T lymphocytes were determined in K^d− or K^d+ cell populations in spleens of mice receiving allo- or syngeneic HCT, respectively (A). Cells were also incubated on anti-CD3–coated plates for 6 hours in RPMI1640 + 10% fetal bovine serum (FBS) containing 1 µg/mL brefeldin A, subsequently stained with anti-CD4 and anti-CD8, and incubated with fluorescent anti-cytokine antibodies. Total numbers of donor-derived, CD4⁺ and CD8⁺ T cells were counted and examined for the production of IFNγ, IL-2, and TNFα (B). Data are representative of 1 of 3 replicate experiments. N = 3 to 4 mice per group. *P < .01, #P < .05 or as otherwise noted.