PDCD1 and Arthritis: Intracellular phospho-STAT3 measurements indeed correlated strikingly with paired BCL3, SOCS3 and PIM1 gene expression in ex vivo CD4+ T cells of early arthritis patients (Fig. 1D–F), but not with that of other genes in the signature such as PDCD1 or IGFL2, which are not known to be induced by STAT3 (supplementary Fig. S1, available at Rheumatology online).