CXCR5 and systemic lupus erythematosus: Our data showed that the absolute numbers of CD4+CXCR5+PD-1+ Tfh cells were not significantly increased in SLE patients than in healthy controls, however the percentage of CD4+CXCR5+PD-1+ Tfh cells were expanded in active SLE patients and that Tfh cell-derived IL-21 contributed to autoantibody production.