Interleukin 9, also known as IL-9, is a cell signalling molecule belonging to the group of interleukins.
IL-9 is produced by variety of cells like mast cells, NKT cells, Th2, Th17, Treg, ILC2, and Th9 cells in different amounts.
Th9 cells are regarded as the major CD4+ T cells that produce IL-9.
Il-9 is a cytokine secreted by CD4+ helper cells that acts as a regulator of a variety of hematopoietic cells.
Il-9 cytokine stimulates cell proliferation and prevents apoptosis.
It functions through the interleukin-9 receptor (IL9R), which activates different signal transducer and activator (STAT) proteins connecting this cytokine to various biological processes.
This cytokine is a determining factor in the pathogenesis of bronchial hyperresponsiveness.
It gives rise to hematologic neoplasias and also Hodgkin’s lymphoma.
IL-9 also has antitumor properties in solid tumors and melanoma.
The human IL-9 gene is located on the long arm of human chromosome 5 at band 5q31-32, a region which is not found in a number of patients with acquired chromosome 5q deletion syndrome.
Interleukin 33 (IL-33) induces IL-9 expression and secretion in T cells.
IL-9 has direct and indirect effects on multiple cell types that affect the development of immunity and inflammation.
IL-9 expression varies in different types of tumours such as Large cell anaplastic lymphoma (LCAL) and Hodgkin’s Disease (HD).