ICOS and systemic lupus erythematosus: The results demonstrated ICOS’s significant discriminative capacity between pSS and RA or SLE, with mean AUC values of 0.9705 and 0.9349 (Figure 6B), and the expression levels of ICOS in RA and SLE were almost close to that of non-pSS while significantly lower than that of pSS (Figure 6H).