Population of lungs by mast cells

Mast cells are tissue-resident cells that are localized particularly in the skin, gastrointestinal tract and respiratory tract. They are mainly recognised for their role in adaptive immunity and allergy where cross-linking of surface-bound IgE results in acute mediator release giving early symptoms, and cytokine production contributing to chronic changes. The mast cell is now also increasingly recognized for its role in innate immunity conferred by its repertoire of complement and Toll receptors. Thus, mast cell deletion has been shown to suppress certain innate immune responses in murine models. Our interest is in the mechanisms involved in population of tissues by mast cells, particularly the airways. Mast cells are released from the bone marrow into the blood as committed precursors. These cells circulate in very low numbers and accumulate in tissues where they proliferate and mature under the influence of local cytokines and growth factors that define the mature phenotype appropriate for their location. Chemoattraction is important at critical phases in the life history of the mast cell, i.e. movement towards and through the bone marrow sinus endothelium, recruitment to tissues and movement within the tissues to the location of the mature cell. These phases are dependent on chemoattractants generated at specific locations acting on cell surface receptors whose repertoire evolves as the mast cell matures.