Abstract
Mast cell progenitors arise in bone marrow and then migrate to peripheral tissues where they mature. It is presumed that integrin receptors are involved in their migration and homing. In the present study, the expression of various integrin subunits was investigated in three systems of adherent and nonadherent mast cells. Mesentery mast cells, freshly isolated bone marrow-derived mast cells (BMMC) and RBL-2H3 cells grown attached to tissue culture flasks are all adherent mast cells and peritoneal mast cells, and cultured BMMC and RBL-2H3 cells grown in suspension represent nonadherent mast cell populations. Pure populations of mast cells were immunomagnetically isolated from bone marrow, mesentery and peritoneal lavage using the mast cell-specific monoclonal antibody AA4. By immunomicroscopy, we could demonstrate that all of these mast cells expressed alpha 4, alpha 5, alpha 6, beta 1 and beta 7 integrin subunits. The expression of the alpha 4 integrin subunit was 25% higher in freshly isolated mesentery mast cells and BMMC. Consistent with the results obtained by immunomicroscopy, mesentery mast cells expressed 65% more mRNA for the alpha 4 integrin subunit than peritoneal mast cells. In vitro studies were also conducted using the rat mast cell line RBL-2H3. RBL-2H3 cells grown attached to the tissue culture flasks or as suspension cultures expressed the same integrin subunits identified in bone marrow, mesenteric and peritoneal mast cells ex vivo. Similarly, the expression of alpha 4 integrin was higher in adherent cells. Therefore, alpha 4 integrins may play a critical role in the anchorage of mast cells to the extracellular matrix in bone marrow and in peripheral tissues.
Highlights
Mast cells are important immunoregulatory and inflammatory cells preferentially found in perivascular connective tissues of multiple organs
We investigated the expression of α4, α5, α6, ß1 and ß7 integrin subunits on adherent and nonadherent populations of mast cells isolated from mouse bone marrow, rat mesentery and rat peritoneal lavage and RBL-2H3 cells, a mast cell line
Integrin subunit expression was analyzed by immunological methods on adherent and nonadherent populations of mast cells isolated from mesentery, peritoneal lavage, and bone marrow and on the mast cell line, RBL2H3
Summary
Mast cells are important immunoregulatory and inflammatory cells preferentially found in perivascular connective tissues of multiple organs. Committed mast cell precursors derived from bone marrow migrate to peripheral tissues where they complete their maturation into phenotypically distinct mast cells [1,2,3,4]. The mechanism underlying differentiation, migration and tissue-specific homing of mast cell precursors is not completely understood. It is presumed that the interaction of specific cell adhesion receptors expressed on the surface of mast cells with extracellular matrix proteins plays an important role [5,6,7]. Integrins are αß heterodimeric transmembrane receptors widely expressed on migratory cells, that mediate cell-extracellular matrix adhesion [8] and are involved in signal transduction pathways modulating diverse cellular processes such as cell migration, differentiation and proliferation [9,10,11,12]. Using the monoclonal antibody (mAb) AA4 [18] that recognizes two derivatives of the ganglioside GD1b [19], which are unique to the surface of rodent mast cells [20], pure populations of mast cells can be isolated [21]
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