LFA-3 is ligand of the t-lymphocyte cd2 glycoprotein. This interaction is important in mediating thymocyte interactions with thymic epithelial cells,antigen-independent and dependent interactions of t-lymphocytes with target cells and antigen- presenting cells and the t-lymphocyte rosetting with erythrocytes. In addition,the lfa-3/cd2 interaction may prime response by both the cd2+ and lfa-3+ cells.