Interleukin are small proteins that are produced by a variety of cell types, especially T cells and other white blood cells, that regulate many aspects of inflammation and the immune response, including stimulating the production of white blood cells and platelets. The function of the immune system depends in a large part on interleukins and rare deficiencies of a number of them have been described, all featuring autoimmune diseases or immune deficiency. The majority of interleukins are synthesized by helper CD4 T lymphocytes, as well as through monocytes, macrophages and endothelial cells. They promote the development and differentiation of T and B lymphocytes and hematopoietic cells. Interleukin may be used to combat some forms of cancer.