Human Cardiac Mast Cells and Their Role in Severe Allergic Reactions

Publisher Summary Within human heart tissue, mast cells lie between myocytes and in close contact with blood vessels. Mast cells are also localized in the coronary adventitia and in the shoulder region of coronary atheroma. The density of cardiac mast cells is higher in patients with dilated and ischaemic cardiomyopathy than in subjects without cardiovascular diseases. Intriguingly, in some of these conditions there is in situ evidence of mast cell activation. Observations by different groups of investigators, suggest that HHMCs play complex and significant roles in various pathophysiological conditions that involve the cardiovascular system. Direct activation of HHMCs by circulating antigens, autoantibodies and therapeutic and diagnostic substances injected intravascularly can explain some of the anaphylactic/anaphylactoid reactions caused by these agents. HHMCs possess Fc ɛ RI, C5a receptors and IgE on their surface, which could explain the direct involvement of cardiac mast cells in systemic and cardiac anaphylaxis. Of particular interest is the observation that the eosinophil cationic proteins ECP and MBP can activate HHMCs to release preformed and de novo synthesized mediators. This novel observation suggests that, in allergic patients with eosinophilia, eosinophilic infiltration and the deposition of eosinophil granule proteins might, through direct activation of HHMCs, contribute to the cardiac derangements observed in some of the patients.