CXCR5 and oral lichen planus: A more recent study found that the peripheral blood of OLP patients has significantly increased CXCR5+CD4+ Tfh-like cell and B cell levels, along with significantly reduced serum IL-21 levels, suggesting that increased circulating Tfh-like cells may participate in OLP pathogenesis via the abnormal regulation of B cell proliferation and IL-21 production [51].