CD4 and systemic lupus erythematosus: In patients with SLE, peripheral CD4+ CXCR5+ PD-1+ Tfh cells (regarded as a GC-Tfh counterpart) are increased and are associated with a more serious disease phenotype, and CCR7− PD-1hi CXCR5+ CD4+ T cells (regarded as an activated Tfh cell phenotype) are associated with elevated autoantibody titers and the disease activity (13, 14).