CXCR5 and systemic lupus erythematosus: A similar population of PD‐1+CXCR5− extrafollicular Th cells, termed Tph cells, have been reported as driving autoantibody production in a mouse model of rheumatoid arthritis and in human SLE (Odegard et al, 2008; Rao et al, 2017; Lin et al, 2019; Makiyama et al, 2019).