Given that the frequency of foxp3+ CD4+ T cells in PBMC of HC was comparable to that in RA PBMC and was even significant lower than that in RA SFMC, impaired expression of IL-1RII in RA memory CD4+ T cells was not likely to be caused by the reduced frequency of Foxp3+ Treg cells (Figure 7—figure supplement 1). Here, CD4 is linked to rheumatoid arthritis.