Differential induction ofSOCS1gene expression in thymocyte subsets. Sorted DN, DP, CD4⁺, or CD8⁺ thymocyte subsets from SOCS1^-/-IFNγ^-/- mice and SOCS1^+/+IFNγ^-/- controls were stimulated with indicated cytokines or were left untreated in medium alone. After 16 hours of incubation, total RNA was isolated and first-strand cDNA was synthesized. cDNAs encoding SOCS1 and G3PDH genes were amplified by PCR, as described in “Materials and methods.” The SOCS1 transcript was absent in SOCS1^-/-IFNγ^-/- cells (not shown).