The interleukins are a family of cytokines (chemical messengers) that include IL-1, IL-d (sometimes called T-cell growth factor), IL-10 and IL-12. IL-1 activates CD4 cells, mediates acute systemic immune symptoms (e.g., fever), and acts on the hyupothalamus (a gland in the brain that helps regulate metabolic rate) to decrease appetite.
- IL-2 promotes the proliferation and activity of CD4 cells, cytotoxic T-lymphocytes, and natural killer cells. IL-2 is associated with cell-mediated immune response. Recombinant IL-2 (aldesleukin, Proleukin) is used for cancer therapy and continues to be studied as an immunomudulatory treatment for Kaposi's sarcoma and HIV disease. Side effects include flu-like symptoms (fever, chills), decreased blood pressure, and anorexia.
- IL-3 is a hematopoietic (blood growth) factor that promotes the growth and differentiation of several types of blood cells (red, white, and platelets).
- IL-4 is released by a subset of CD4 cells, and helps stimulate antibody production.
- IL-6 is produced by macrophages and mediates acute systemic immune responses (e.g., fever).
- IL-8 stimulates the growth of new blood vessels.
- IL-10 stimulates the proliferation and activity of B-cells (which produce antibodies), modulates macrophage function, and enhances humoral macrophage function, and enhances humoral (TH2) immunity, while suppressing cell-mediated immune function.
- IL-12 is produced by various immune cells (e.g., monocytes, macrophages, dendritic cells, and neutrophils), and activates natural killer cells and cytotoxic T-lymphocytes and induces the production of interferon-gamma. IL-12 is associated with the cell-mediated immune response.