Impaired expression of cyclin D3 and cdk4 in stimulated T cells cultured in the absence of l-Arg. (A-B) Whole-cell lysates were obtained from 3 × 10⁶ activated T cells cultured in the presence or the absence of l-Arg for various lengths of time (hours) or from activated T cells cultured in the absence of l-Arg for 24 hours and then replenished with l-Arg at 48 or 72 hours. The expression of cyclin and cdks was tested by Western blotting. (C) Lysates from stimulated T cells cultured for 24 hours were prepared and 100 μg was immunoprecipitated with agarose-conjugated anti–cyclin D3 and anti-cdk4. Immunoprecipitates were then tested for cyclin D3 and cdk4 expression by Western blotting.