Cytokines involved in growth and differentiation of human basophils and mast cells.

Mast cells and basophils are multifunctional effector cells of the immune system. Both are myeloid cells and originate from multipotent hemopoietic progenitor cells. Usually, human basophils complete their differentiation in the bone marrow. In contrast, mast cells usually undergo differentiation in extramedullary organs. During the past few years, growth factors for human basophils and a growth factor for human mast cells have been identified. Interleukin-3 is the most potent differentiation factor for human basophils and activates mature basophils via high affinity binding sites. Other basophil agonists are GM-CSF, IL-5, NGF and certain chemokines (IL-8, MCP-1). Mast cells apparently loose cytokine binding sites during mastopoiesis and as mature cells, do not express detectable amounts of IL-3R, GM-CSFR or IL-8R. However, in contrast to other myeloid cells, mast cells express SCF receptor/c-kit during mastopoiesis and on mature cells. Furthermore, the ligand of c-kit, SCF, induces differentiation of human mast cells from their progenitor cells and upregulates effector functions in mature mast cells.