As the TC lupus-prone model (16), W.Yaa mice presented an expanded population of CD4+CD44+FOXP3–CXCR5+BCL6+CD162lo/–PD-1+ Tfh cells as well as follicular Tregs (CD4+CD44+FOXP3+CXCR5–BCL6–CD162lo/–PD-1+ Tfr), with a skewed Tfh/Tfr ratio, none of which were altered by DON (Figure 2, A–C). Here, CD4 is linked to systemic lupus erythematosus.