SDC1 and systemic lupus erythematosus: Peripheral blood mononuclear cells (PBMCs) from 42 SLE patients and 22 matched healthy subjects were collected to assess proportions of circulating CXCR5+PD1+/CD4+ T cells (Tfh), CD4+CCR6+ T cells (Th17-like) and CD19+CD138+ plasma cells by flow cytometry.