Interleukin Family (IL)

Jennifer Fries

The Interleukins comprise a disparate group of cytokines and growth factors that are produced by and released from leukocytes. Interleukin-1β (1L-1β) is released primarily from stimulated macrophages and monocytes and plays a key role in inflammatory and immune responses and may induce anti-tumor immunity. It activates T cells to proliferate and secrete IL-2. IL-2 is also known as T cell growth factor since it promotes longterm growth of activated T cells, activation and proliferation of natural killer (NK) cells and induction of INF-γ and B cell growth factor secretion. IL-3 is a colony-stimulating factor that induces colony formation of macrophages, neutrohils, mast cells, and megakaryocytes from hematopoietic progenitor cells. IL-3 also interacts with IL-2 to stimulate growth of T cells and to induce IgG secretion from activated B cells. IL-4 is produced by T cells and stimulates the growth and differentiation of immunologically competent cells and activates helper T cell (Th2) function. IL-5 is a hematopoietic cytokine that stimulates the proliferation, differentiation, and survival of eosinophils. It is also involved in B cell growth and antibody production and in the generation of cytotoxic T cells. IL-6 is a multifunctional cytokine that is involved in the regulation of the acute-phase immune system response to infection and injury. IL-7 is a lymphoid cell growth factor that induces proliferation of pre-B, pro-B, and early T cells as well as certain leukemia and lymphomas. IL-8 is a chemokine of the CXC family that is chemotactic for neutrophils and induces the release of hematopoietic progenitor cells from bone marrow. IL-10 is produced by the Th2 cells, B cells, macrophages and keratinocytes. It is anti-inflammatory in that it inhibits the synthesis of cytokines in target cells at the mRNA transcription or translation level. However, it also enhances the function of B cells and cytotoxic T cells. IL-12 is produced predominantly by monocytes and NK cells and induces T cells and NK cells to produce IFN-γ. IL-12 has antiangiogenic properties. IL-13 is produced predominantly by Th2 cells and induces B cell proliferation and differentiation. IL-15 is a cytokine produced in macrophages and T cells that enhances T cell proliferation and maintains CD8 (+) cytotoxic T cell survival.

Figure 1. Interleukin 16 (IL-16), also know as lymphocyte chemoattractant factor LCF, is a proinflammatory cytokine that is chemotactic for CD4+ T lymphocytes, monocytes, and eosinophils.

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