Reduced SOCS3 but not SOCS1 expression in gcsfr-d715 mice. WT mice and gcsfr-d715 littermates were injected with vehicle or G-CSF for 4 consecutive days. (A-B) RNA was isolated, and SOCS1 (A) and SOCS3 (B) transcript levels were measured by quantitative RT-PCR. Expression of ribonuclease inhibitor was used for normalization of the data. SOCS levels were expressed relative to untreated WT mice. Data shown are mean + standard error of the mean (SEM) of 3 experiments. *Difference between WT and G-CSF-R–d715 is significant; P < .05 by Student t test. (C) SOCS3 expression in bone marrow cells deprived of growth factor for 4 hours and then stimulated with G-CSF in vitro for the indicated times. SOCS3 levels were expressed relative to growth factor–deprived cells. Data shown are mean + SEM of 4 experiments; differences between WT and G-CSF-R–d715 are significant (Student t test, P < .05).