IL-7 stimulation suppresses IL-7Rα gene expression, and mRNA levels increase upon cessation of cytokine treatment. (A) The levels of IL-7Rα transcripts were assessed in CD4⁺ RTEs stimulated with doses of rIL-7 ranging from 0.01 to 100 ng/mL. After 0, 24, 72, and 120 hours of culture, total RNAs were extracted and reverse transcribed. cDNAs were amplified with primers specific for IL-7Rα and GAPDH. The relative level of mRNA transcripts was assessed by real-time PCR in duplicate samples and the mean number of molecules of IL-7Rα (±SD) relative to GAPDH at each time point are shown on semilogarithmic graphs. (B) IL-7Rα mRNA levels were monitored in nonstimulated and IL-7–stimulated (10 ng/mL) RTEs after 0, 1, 24, 72, and 120 hours of culture. After 24 hours and 72 hours of culture in the presence of rIL-7 (10 ng/mL), some cultures were washed and incubations were continued for an additional 48 hours in the absence of rIL-7. IL-7Rα mRNA was assessed at the indicated time points and is labeled as “IL-7 withdrawal.”