Overexpression of SOCS-1 hinders pre-TCR–driven expansion of immature thymocytes.

Fetal thymic lobes from RAG2^−/− mice were infected with the indicated retrovirus constructs for 2 days and subsequently cultured for a further 6 days in the presence of anti-CD3ε mAb. Single-cell suspensions were obtained from fetal thymic lobes and analyzed for surface expression of CD4 and CD8; percentages of cells in each quadrant are shown. Results obtained for uninfected (GFP⁻) and infected (GFP⁺) donor cells are presented; cell counts for the absolute number of GFP⁺ cells per lobe are shown in parentheses. The ratio—calculated from the total thymic cellularity—of infected cells (GFP⁺) to uninfected cells (GFP⁻) expressing CD4/CD8 coreceptors is provided.