IL15 is a pleiotropic cytokine that orchestrates innate and adaptive immune responses through a distinctive signaling mechanism. Unlike most cytokines, IL15 associates with its high-affinity receptor IL15RA during biosynthesis and is trans-presented to target cells expressing IL2RB and IL2RG receptor subunits, triggering JAK1/JAK3-dependent phosphorylation of STAT3 and STAT5. This architecture enables IL15 to stimulate proliferation of natural killer cells, T cells, and B cells, and to promote production of chemokines such as IL8 and CCL2 in monocytes. IL15 is implicated in multiple autoimmune and inflammatory conditions, including coeliac disease, where overexpression in gut epithelium and lamina propria drives villous atrophy in the presence of gluten and HLA-DQ8 1. IL15 also plays a pathogenic role in psoriasis, where dysregulated signaling contributes to dendritic cell-mediated inflammation 2. Clinically, IL15 has emerged as a potent enhancer of cell-based cancer immunotherapy. IL15-engineered CAR T cells targeting GPC3 demonstrated a 66% disease control rate and 33% objective response rate in patients with solid cancers 3, while IL15-secreting CAR-NK cells prolonged survival in acute myelogenous leukaemia models 4. Combination therapy with checkpoint inhibitors, monoclonal antibodies, and CD40 agonists amplifies IL15's anti-tumour effects 5. The IL15-targeting monoclonal antibody ordesekimab represents the first approved therapeutic targeting this pathway.