Immune reconstitution is intact in Cdk5^−/−Chematopoietic chimeras. The spleen, LNs, and thymus were harvested from naive, fully engrafted, Cdk5^+/+C (WT), and Cdk5^−/−C (KO) mice and either sectioned and stained for anatomical evaluation (spleen and LN [A]) or enzymatically digested, dispersed into single-cell suspensions, stained for CD4 and CD8, and examined by flow cytometry (spleen and thymus [B]). No differences between groups were noted in architecture, cellularity, or CD4⁺ and CD8⁺ phenotypes. The numbers of nTregs in spleen were determined by staining single-cell suspension with CD4 and CD25 on surface followed by intracellular staining of FoxP3 (C). Vβ usage in T-cell populations was determined by staining single-cell suspensions of splenocytes with Vβ antibodies in combination with anti-CD4 and anti-CD8 (D). No differences in splenic Treg numbers or Vβ usage were noted. N = 3 to 6 mice per group. CD4⁺ and CD8⁺ T cells from or Cdk5^−/−C mice were cultured with B6D2F1 splenic DCs for 96 hours and examined for proliferative capacity (E) and cytotoxicity (F) when ³H-thymidine–labeled, allogeneic (P815) or syngeneic (EL4) tumor cells were added. Data are representative of 1 of at least 3 replicate experiments. *P < .05. CPM, counts per minute.