CD200R1 and systemic lupus erythematosus: We found that, while the effect of the CD200-CD200R1 pathway on the T cells in HCs was negligible (see Additional file 6), CD200-Fc but not anti-CD200R1 reduced the percentage of Th17 cells (P < 0.05; Figure 4) in SLE patients, suggesting a role for CD200/CD200R signaling in regulating Th17 cell differentiation.