Induction of CXCR5, ICOS, and BCL6 by IL-12 in CD4⁺ T cells is independent of STAT3. (A-D) Naive CD4⁺ T cells isolated from healthy donors and STAT3_MUT patients were cultured with anti-CD2/CD3/CD28 Abs in the absence (nil) or presence of Th1-polarizing conditions (+IL-12). After 4 days the cells were harvested, and surface expression of CXCR5 and ICOS was determined by flow cytometry and of TBX21 and BCL6 by qPCR. (A,C) representative histogram plots from 1 healthy donor and 1 STAT3_MUT patient. Expression of (B) CXCR5 (n = 3), (D) ICOS (n = 3), (E) TBX21 (n = 4), and (F) BCL6 (n = 5) after Th1 polarization is presented as fold-increase compared with the nil culture in each experiment. (B,D-F) The graphs represent the mean ± SEM of the indicated number of experiments.