DEVELOPMENT OF MAST-CELLS AND BASOPHILS - PROCESSES AND REGULATION MECHANISMS

Mast cells and basophils are offspring of the multipotential hematopoi etic stem cell. Although mast cells sometimes are misunderstood as bas ophils that have invaded connective or mucosal tissue, these two kinds of basophilic cells are distinguishable by morphology and surface ant igenicity. Developmental processes of mast cells and hasophils are dif ferent. Basophils complete their differentiation within the bone marro w, but precursors of mast cells leave the bone marrow, invade connecti ve or mucosal tissue, proliferate, and differentiate into mast cells. The mechanisms regulating development are different between mast cells and basophils. Both T cell-dependent and fibroblast-dependent mechani sms are involved in the development of rodent mast cells, but only the fibroblast-dependent mechanism is known for development of human mast cells and only the T cell-dependent mechanism for the development of basophils of both rodents and humans. The most important cytokine for the T cell-dependent mechanism appears to be interleukin-3, whereas fo r the fibroblast-dependent mechanism it appears to be the ligand for t he c-kit receptor (ie, stem cell factor).