Fig. 3.

Cdc42 deletion leads to T-cell hyperproliferation and hyperactivation. (A and B) Depletion of Cdc42 causes hyperproliferation in vitro. Purified splenic naive T cells were cultured with or without the indicated dosage of plate-bound anti-CD3 antibody together with 2 μg/mL anti-CD28 antibody. Culture supernatant was collected for analysis of IL-2 by ELISA at day 1 (B). The cells were cultured for another 48 h and assessed for cell growth rate as described in the text. The data were normalized to that of WT T cells in the absence of anti-CD3 and anti-CD28 antibodies (A). (C) Cdc42 depletion up-regulates the T-cell activation marker CD69. Splenocytes were stained with anti-CD4, anti-CD8, anti-TCRβ, and anti-CD69 antibodies. CD69 expression in T cells was analyzed by flow cytometry. (D) Cdc42 deficiency results in accelerated cell proliferation in vivo. Cdc42-deficient and WT Mice were injected i.p. with BrdU. Splenocytes were isolated 12 h later and analyzed for BrdU incorporation in CD4⁺ and CD8⁺ naive T cells. Data are shown as means ± SD; n = 5. *P < 0.05; **P < 0.01.