The HM48-1 monoclonal antibody specifically reacts with mouse CD48, a GPI-anchored molecule in the Ig superfamily. CD48 was previously known as BCM1 in mice, Blast-1 in humans, and OX-45 in rats. Its ligands are CD2 and CD244 and it is expressed on leukocytes to the exclusion of non-hematopoietic cells. The utilization of the HM48-1 antibody has been reported to prolong cardiac allografts survival in in vivo studies. The antibody blocks the interaction of CD2 and CD244, inhibits CTL priming, and blocks the binding of soluble CD2 to CD48 expressing cells.