Full-length STAT5α proteins are expressed in both FDC-P1 and FDC-P1(M) cells. (A) FDC-P1 and FDC-P1(M) cells were grown in IL-3–containing medium (Med) or starved for 20 hours (−) and stimulated with IL-3 (+) for 30 minutes. Cytosolic extracts were analyzed by Western blotting using anti-STAT5 antibodies (89p). (B) The nitrocellulose filter shown in (A) was stripped and reprobed with anti-STAT5 antibodies directed against the C-terminus of STAT5. Locations of full-length (α) and truncated (β) STAT5 proteins are indicated on the right.