As such, experiments using blood CD4+ T-cells showed no (low levels of) detectable basal expression of cytokines by intracellular flow cytometry (IL2, IL10, IFN, TNF, or IL17) between HC and RA, while following activation, a higher percentage of positive cells were indeed observed in RA [46,47,48]. Here, IFNA1 is linked to rheumatoid arthritis.