MIF and rheumatoid arthritis: Studies have shown that the shedding of CD74 extracellular domain may lead to a marked increase in serum CD74 levels in RA patients (29).Therefore, we hypothesized that the activation of MIF signaling pathway (MIF-CD74 + CXCR4) in the microenvironment of RA patients affects the communication between T cells and other immune cells, and that the high expression of CD74 in the cell population warrants further investigation as a key mediator of cell signaling.