Xia et al. found that increased histone H3 acetylation of the IL17a promoter could promote Th17 and γδ T17 cell differentiation, which contributed to the immune imbalance and development of psoriasis.281 Using a mouse model, Li et al. found that TNF could inhibit both G9A and CLP, which are methyltransferases of H3K9, by altering the level of phosphorylation of related proteins in keratinocytes, thereby decreasing the level of H3K9 methylation and increasing the level of IL-23.337 Recently, medications targeting histone modifications have become a hot spot of studies. The gene discussed is IL17A; the disease is psoriasis.