(A and B) Proliferative response of Ba/F3–gp130–IL-6R cells cultured for 2 days in the presence of exogenous rhCTRP4 (100 ng/mL), OSM (100 ng/mL), IL-6 (10 ng/mL), IL-3 (10 ng/mL), rhCTRP4 plus IL-6, or OSM plus rhCTRP4, or left untreated (A). (B) Proliferative response of Ba/F3-gp130 cells cultured for 2 days with OSM (100 ng/mL), IL-6 (10 ng/mL), rhCTRP4 (100 ng/mL), hyper–IL-6 (10 ng/mL), a combination of IL-6 (10 ng/mL) and IL-6R (10 ng/mL), a combination of IL-6 and IL-6R plus rhCTRP4, hyper–IL-6 plus rhCTRP4, or IL-3 (10 ng/mL). The proliferation in indicated culture conditions was determined by the colorimetric CCK8 assay. Results are shown as RLUs and normalized to the growth of cells cultured in medium. (C) Purified WT CD4⁺ cells were activated with hyper–IL-6 (10 ng/mL) prior to treatment with rhCTRP4 for 1 hour or without treatment as control. Western blot was performed to analyze the activation of STAT3. (D) Naive CD4⁺ T cells were differentiated toward Th17 cells with TGF-β plus the combination of IL-6 (10 ng/mL) and IL-6R (10 ng/mL) in the presence or absence of rhCTRP4 (100 ng/mL) or differentiated toward Th17 cells with TGF-β and hyper–IL-6 (10 ng/mL) in the presence or absence of rhCTRP4 (100 ng/mL). Data are represented as mean ± SEM and are from 1 of 3 independent experiments with similar results. (A, B, and D) Statistical significance was determined using 1-way ANOVA with Tukey’s post test.**P < 0.01.