In another study, the frequency of CD4+CXCR4+ T cells was increased in the blood, and bronchoalveolar lavage fluid of MDA5+ DM patients, and these T cells can promote pulmonary fibroblast proliferation via interleukin-21 (IL-21), suggesting a potential pathogenic role in MDA5+ DM18. The gene discussed is IFIH1; the disease is dermatomyositis.