The γc family of cytokines is not required for transition to the CD4⁺CD8⁺ stage.

(A) The IL-7–dependent cell line B23 was infected with the MIEV–SOCS-1 retroviral vector or with the empty MIEV vector as control. Stably infected cells were obtained by sorting for GFP expression. Cells were then cultured for the indicated time and pulsed with [³H]thymidine for 6 hours to measure cell proliferation. Mean values ± SD for triplicate samples are given. (B) Newborn RAG2^−/− andRAG2^−/− × γc^−/− mice were injected with anti-CD3ε mAb or with control Ab (Armenian hamster [Ahm] IgG). After 3 days, single-cell suspensions were prepared from the thymus and analyzed for surface expression of CD4 and CD8 by flow cytometry; percentages of cells in each quadrant are shown. Absolute cell numbers were calculated (mean ± SD) from 3 to 6 mice of each genotype. (C) Role of SOCS-1 during early T-cell development. A simple scheme of early T-cell development is shown that is adapted from Di Santo et al36; solid and dashed lines indicate where overexpression of SOCS-1 affects a complete or partial block in T-cell development, respectively. Bold circles represent cycling cells.