SKG mice failed to develop RA‐ILD under specific‐pathogen‐free (SPF) conditions despite the fact that thymic production of autoimmune CD4+T cells persisted in the periphery, but intraperitoneal injection of zymosan especially β‐glucans can cause the development of an RA‐ILD clinical phenotype in the same condition above mentioned.41 This evidence concerns the gene CD4 and interstitial lung disease.