Expression of beta 2 integrin (CD18) in embryonic mouse and chicken heart

Integrins are heterodimeric receptors composed of á and â transmembrane subunits that mediate attachment of cells to the extracellular matrix and counter-ligands such as ICAM-1 on adjacent cells. â2 integrin (CD18) associates with four different á (CD11) subunits to form an integrin subfamily, which has been reported to be expressed exclusively on leukocytes. However, recent studies indicate that â2 integrin is also expressed by other types of cells. Since the gene for â2 integrin is located in the region of human chromosome 21 associated with congenital heart defects, we postulated that it may be expressed in the developing heart. Here, we show the results from several different techniques used to test this hypothesis. PCR analyses indicated that â2 integrin and the áL, áM, and áX subunits are expressed during heart development. Immunohistochemical studies in both embryonic mouse and chicken hearts, using antibodies directed against the N- or C-terminal of â2 integrin or against its á subunit partners, showed that â2 integrin, as well as the áL, áM, and áX subunits, are expressed by the endothelial and mesenchymal cells of the atrioventricular canal and in the epicardium and myocardium during cardiogenesis. In situ hybridization studies further confirmed the presence of â2 integrin in these various locations in the embryonic heart. These results indicate that the â2 integrin subfamily may have other activities in addition to leukocyte adhesion, such as modulating the migration and differentiation of cells during the morphogenesis of the cardiac valves and myocardial walls of the heart.

The Effect of rhG-CSF and rhGM-CSF on Expression of Fc gamma Receptors and beta2 Integrin and Respiratory Burst Function in Human Granulocytes

PURPOSE: Receptors for the Fc of IgG(FcvR) and a beta2 integrin molecule, CD11c/CD18 are important in clearance of microbes by granulocytes. We performed an in vitro study on the effect of recombinant human granulocyte colony-stimulating factor(rhG-CSF), or granulocyte-macrophage colony-stimulating factor(rhGM-CSF) on the expression of Fc R II, Fc R III, CD11c and CD18 and respiratory burst function of granulocytes. METHODS: Peripheral blood was collected from six healthy adults. The isolated granulocytes were stimulated with rhG-CSF, 250mg/mL, rhGM-CSF, 100ng/mL or both of them for 1, 3, 9, 24, and 48 hours. Using flow cytometry, we compared the expression of the Fc R II, Fc R III, CD11c and CD18 of granulocytes before and after stimulation. We also the studied respiratory burst of granulocytes with chemiluminescence assay. RESULTS: Fc R II and CD18 expression were not changed significantly after stimulation. Fc R III expression was decreased significantly after stimulation with rhG-CSF, rhGM-CSF, or both of them. CD11c expression was increased initially but was found to decrease significantly after 9 hours of stimulation. Granulocytes treated with rhG-CSF, rhGM-CSF, or both displayed enhanced respiratory burst. Our results suggest that exposure of granulocyte to growth factor results in granulocyte activation. CONCLUSION: We have shown that rhG-CSF and rhGM-CSF resulted in an activation of peripheral blood granulocytes immunophenotypically and functionally.