Western blot analysis with anti-phospho-CrkL, anti-phospho-Jak1, and anti-CrkL polyclonal antibodies. A, Murine T cells purified from lymph nodes as described in Materials and Methods were incubated with or without IL-7 for the indicated times. Representative of 3 experiments; B, Human T lymphocytes purified as described in Materials and Methods were incubated with or without IL-7 for the indicated times. Representative of 3 experiments; C, Pro-B cells purified from spleens of Rag1-deficient mice as described in Materials and Methods were incubated with or without IL-7 for 15 min. Representative of 3 experiments; D, Coimmunprecipitation on cell lysates from unstimulated and IL-7 stimulated human T cells was performed with anti-CrkL antibody as described in Materials and Methods. Blots were probed with anti-Stat5 and anti-CrkL antibodies. Representative of 3 experiments.