CD28 and rheumatoid arthritis: To test the hypothesis that genetically driven GNG4 expression modulation may be associated with differential RA susceptibility, we reanalyzed data from a recent expression quantitative trait locus (eQTL) study—which relates genetic variation to gene expression levels—in human nnCD4 T cells before and after anti-CD3/CD28 stimulation (data file S9) (158).