Interleukin-1a (IL-1a) is largely responsible for inflammation, fever and sepsis. It activates TNF-a and the work very closely together. Their cofunctions include PGE2 synthesis, nitric oxide production, insulin resistance and IL-8 and chemokine production.
Interleukin-1b (IL-1b) has been implicated in several autoinflammatory syndromes. It is also important in cell proliferation, differentiation and apoptosis. Its induction of COX2 cytokine in the nervous system contributes to inflammatory pain hypersensitivity.
Interleukin-2 (IL-2) is crucial in prevention of autoimmune disease by regulating T cell differentiation. It is also thought to be involved in itchiness and psoriasis. IL-2 is used in the treatment of cancers.
Interleukin 3 (IL-3) drives the differentiation of multipotent hematopoietic stem cells into myeloid progenitor cells. If IL-7 is also present, they can work synergistically to trigger differentiation into lymphoid progenitor cells. IL-3 induces proliferation of all myeloid cells (including mast cells) along with other cytokines like IL-6. It supports growth and differentiation of T cells from bone marrow when an immune response is triggered.
Interleukin 4 (IL-4) changes naïve T cells to T helper cells, which secrete chemicals to drive actions of other immune cells. T helper cells then secrete additional IL-4 to perpetuate the cycle. IL-4 participates in the airway inflammation seen in allergic asthma.
Interleukin 5 (IL-5) encourages growth of B cells and antibody secretion as well as eosinophil activation. It is heavily involved in allergic diseases, particularly those in which eosinophils are notably increased. Mepolizumab is a monoclonal antibody against IL-5 that can reduce excessive eosinophils.
Interleukin 6 (IL-6) mediates fever and the acute phase inflammatory response. It is secreted to stimulate bone resorption and inhibitors of IL-6 are used to treat osteoporosis (including estrogen.) It inhibits TNF-a and IL-1. Unusually, it also has anti-inflammatory behaviors, particularly during exercise in the muscle.
Interleukin 9 (IL-9) increases cell proliferation and impedes apoptosis, cell death, of hematopoietic cells. It is particularly important in asthma and bronchial hyperresponsiveness.
Interleukin 10 (IL-10) is an anti-inflammatory molecule involved in regulating the JAK-STAT pathway. It counteracts many of the inflammatory effects of mast cells, often by interfering with production of substances like interferons and TNF-a. Exercise increases levels of this molecule.
Interleukin 13 (IL-13) is critical in initiation of airway disease. It induces matrix metalloproteinases to act. IL-13 can also induce IgE release from B cells. It is effectively a link between allergic inflammatory cells and the non-immune cells they interact with. Excessive , IL-13 causes airway hyperresponsiveness, goblet cell metaplasia and oversecretion of mucus.