CXCR4 and autoimmune disease: Moreover, compared to rN and IM cells, aN and dnCS B cells in APs expressed a lower level of CXCR4, which is critical for GC reaction, and higher level IL‐21R (Figure 1E,F), which promotes B cells to differentiate into PBs through the EF pathway in autoimmune disease.35, 36, 37, 38