ROLE FOR INTERLEUKIN-3 IN MAST-CELL AND BASOPHIL DEVELOPMENT AND IN IMMUNITY TO PARASITES

The cytokine interleukin-3 (IL-3), which can be derived from T cells a nd other sources, is a potentially important link between the immune a nd haematopoietic systems(1). IL-3 may be particularly critical for th e development, survival and function of tissue mast cells(1-6) and blo od basophils(7,8), which are thought to be important effector cells in immunity to parasites and other immunological responses, such as alle rgic reactions(9). Here we show using IL-3-deficient mice(10), that IL -3 is not essential for the generation of mast cells or basophils unde r physiological conditions, but that it does contribute to increased n umbers of tissue mast cells, enhanced basophil production, and immunit y in mice infected with the nematode Stronglyoides venezuelensis, Para site expulsion and mast-cell development are impaired even more severe ly in IL-3-deficient mice that also show a marked reduction in signall ing by c-kit, These findings establish a role for IL-3 in immunity to parasites and indicate that one of the functions of IL-3 in host defen ce against infection is to expand populations of haematopoietic effect or cells.