Anti-CD26 aAbs are naturally present in serum and seem related to other functional aAbs targeting GPCRs (Cabral-Marques and Riemekasten 2017) because its antigen, soluble DPP4 (sCD26) binds to the GPCR PAR-2 at least in neutrophils (White et al. 2018) and monocytes (not shown), and also because they are dysregulated in patients with rheumatic (Cabral-Marques and Riemekasten 2017) and other autoimmune diseases (Shah 2012). This evidence concerns the gene DPP4 and autoimmune disease.