The growth and differentiation of mast cells

Mast cells (MCs) are local immune cells involved in host defense mechanisms and allergic response. They usually develop from MC committed progenitor cells which in turn are derived from uncommitted hemopoietic stem cells. MC precursors are supposed to develop in the bone marrow (bm) cavities as well as in extramedullary tissues. MC precursor cells also have the potential to circulate in the blood stream. After homing in the tissues they give rise to mature MCs. Recruitment and differentiation as well as terminal maturation of MCs is regulated by a complex network of factors. Two major arms of control have been delineated based on in vitro studies and experimental animal models. The first involves the response of the progenitor cells to growth inducing cytokines, such as IL-3. This type of control promotes the generation of MC precursor cells. The second arm of control involves the microenvironmental network interacting with the MC progenitors. It consists of both stroma cell- and immune cell-derived differentiation factors and the direct interaction of cells. It may be important for homing of MC progenitors during embryogenesis and probably throughout life. The stromal component also determines terminal differentiation towards a particular type of MCs and also supports in vitro development of MCs in long term cultures. Growth and function of the mature MCs in the various tissues may be triggered by additional factors including the interactions of MCs with other leukocytes and nerve cells. The coupling of MC activation processes with subsequent proliferation may be a triggering factor in allergic disease. This article attempts to provide a synthesis of current knowledge on MC development.(ABSTRACT TRUNCATED AT 250 WORDS)