In this context, excessive amounts of IL-15 ﻿lead to increased expression of major histocompatibility complex class (MHC) II and ﻿reduced expression of the suppressor of cytokine signaling (SOCS) 3 in macrophages, which activate the proliferation of autoreactive CD4+ T cells in RA (36). Here, IL15 is linked to rheumatoid arthritis.