Role of laminin in localization of human dermal mast cells

Human connective tissue type mast cells (CTMC) are frequently located in close proximity to microvascular and neural basement membranes (BM). We have explored the interaction between human dermal connective tissue-type (chymase positive) mast cells and laminin, a component of BM. In this report, we document that normal CTMC express laminin receptors and are intimately associated with laminin of BM in vivo and pericellular laminin complexes in vitro. Upon degranulation in vitro, CTMC-laminin complexes dissociate and CTMC do not adhere to laminin substrates. In cutaneous mastocytosis/urticaria pigmentosa, CTMC do not express laminin receptors detectable by immunohistochemistry, and are frequently not in close association with laminin of vascular BM. These same features could be induced by degranulation of normal mast cells in organ culture. These findings indicate that CTMC-laminin interactions may be important determinants of mast cell localization in tissue compartments.