CD58, also known as lymphocyte function-associated antigen (LFA-3) is a cell-bound immunoglobulin superfamily receptor with only one known ligand, CD2. CD58 is widely expressed on human hematopoietic and non-hematopoietic tissues, leukocytes, erythrocytes, endothelial and epithelial cells, and fibroblasts. The engagement of CD58 with CD2 optimizes immune recognition and initiates T cell expansion and activation. These contact activities can occur between helper T cells and antigen-presenting cells and cytolytic effectors and target cells.