We did not find any correlation between BTLA expression by lupus aTregs and circulating TFH frequencies (not shown), but this result is consistent with the fact that there was no significant altered distribution of cTFH (defined as CD45RA-CXCR5+ CD4+ T cells) in our lupus cohort compared to HC. Here, CXCR5 is linked to systemic lupus erythematosus.