GC and immunodeficiency disease: The γc family of cytokines, including IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21, holds a crucial position in lymphocyte development, growth, and survival, impacting immune responses across a spectrum of conditions, from cancer to immunodeficiency, allergies, and autoimmune disorders.217,239,240 The γc gene is located on the X-chromosome and expressed in the majority of lymphocyte populations.