ICOS and systemic lupus erythematosus: The functional alterations of cTfh cells in SLE are not well understood, though several studies have reported an increased frequency of activated ICOS+ cTfh cells in active SLE (8), or a shift in the balance of cTfh subsets, with cTfh2 and cTfh17 being overrepresented compared with cTfh1 in adult SLE (11).