IL15 and sarcoidosis: Furthermore, the process of T cell activation has been observed to stimulate the formation of granulomas via the actions of IL-12, IL-15, and monocyte colony-stimulating factor, which are generated from macrophages.[1,2] Research has indicated that MHC-2 gene variation is associated with the susceptibility, phenotype and prognosis of patients with sarcoidosis.[3] Nevertheless, the question of whether other genes have an impact on sarcoidosis, and the manner in which they might do so, remains unresolved.