Remarkably, Treg subsets were consistently upregulated in all diseases relative to HV, except for the percentages of Inducible T-cell Costimulator (ICOS)+ Tregs among Tregs that were downregulated in 10 diseases (APLS, CD, CS, FMF, GPA, OA, RA, SLE, TA, and UC). Here, ICOS is linked to systemic lupus erythematosus.