One of a group of related proteins made by leukocytes (white blood cells) and other cells in the body. Interleukin-10 is made by activated macrophages and by some T lymphocytes. It reduces inflammation by blocking production of cytokines by immune cells. Interleukin-10 also increases antibody production by plasma cells and helps them live longer. Interleukin-10 made in the laboratory is used as a biological response modifier to boost the immune system. It is a type of cytokine. Also called IL-10.