Role of mast cells in innate and adaptive immune response

Mast cells are well known as mediators of potentially life-threatening anaphylaxis. Beneficial functions of these cells are far less understood. Most of current textbook knowledge on mast cell in vivo functions stems from experiments in mast cell-deficient kit mutant mice as models of mast cell-deficiency and their reconstitution with in vitro-differentiated mast cells. Using novel Cre/loxP-based (and kit independent) models of mast cell-deficiency and mast cellspecific gene inactivation, which we recently generated, we found that mast cells are essential promoters of the T cell response to organic haptens. This finding is at conflict with published literature reporting, based on experiments in kit mutant mice, that mast cells suppress these responses. We conclude that results obtained in kit mutant mice, even if validated by mast cell reconstitution, do not necessarily reflect the situation in normal mice. Therefore, we consider the important question whether mast cells play relevant roles in innate immunity as well as T cell and humoral responses still open. The aim of the project is to re-address the contribution of mast cells in classical models of innate defense against bacterial pathogens and adaptive immune responses.