FIG. 3.

Both IRS-2 and Stat6 contribute to IL-4-induced proliferative responses. (A) FACS-purified CD4⁺/CD62L-high T cells were cultured in submitogenic PMA (2 ng/ml) supplemented with increasing doses of IL-4 (open symbols) or with plate-bound anti-CD3 and anti-CD28 (solid symbols). The proliferative response was determined by [³H]thymidine incorporation from a 48-h culture. The error bars indicate standard deviation. (B) Enriched T lymphocytes were cultured for 48 h in the presence of submitogenic PMA and 10 ng of IL-4/ml or 50 ng of PMA/ml and 500 ng of ionomycin/ml (P+I). p27kip1 (p27) protein levels were detected in whole-cell extracts by immunoblotting. The blot was stripped and reprobed with antibody specific for cdk2. Unt, untreated. (C) Enriched T lymphocytes were cultured in the presence or absence of submitogenic PMA (2 ng/ml) and 10 ng of IL-4/ml for 1 h. RNA was prepared, and c-myc expression was determined by Northern blot analysis. The blot was stripped and reprobed with γ-actin.