Lymphocytes Utilize CD11b/CD18 for Adhesion toCandida albicans

Large granular lymphocytes require adherence to hyphae ofCandida albicansto inhibit growth of this fungus. This study was undertaken to identify the lymphocyte surface structures that mediate this adhesion. Monoclonal antibodies specific for epitopes of the α subunit (CD11b) and the β2subunit (CD18) of Mac-1 eliminated lymphocyte adhesion toC. albicanshyphae. Significant inhibition of lymphocyte adhesion toC. albicanswas also achieved with known protein ligands of Mac-1. These proteins included the extracellular matrix proteins vitronectin, laminin, and fibrinogen as well as two engineered peptides containing RGD (arginine–glycine–aspartic acid) sequences. Carbohydrates includingN-acetyl-D-glucosamine which have been demonstrated to inhibit Mac-1-mediated adhesion to whole yeast and yeast zymosan also blocked lymphocyte adhesion to hyphae. These results identify Mac-1 (CD11b/CD18) as the surface structure that mediates lymphocyte adhesion toC. albicans.A model is proposed for lymphocyte Mac-1 activation by microbial ligands.