Anti-CD45 is a combination in equal amounts (weight for volume) of two monoclonal antibodies that are directed to non-overlapping epitopes on human CD45. It is a purified, concentrated, and sterile gamma globulin, primarily monomeric IgG, produced from the supernatant of the two rat IgG2b hybridoma clones, YTH 24 and YTH 54. The hybridomas were produced as fusions between splenocytes from DA rats immunized with human leukocytes and the rat myeloma line Y3. The combination of the two MAbs exerts a synergistic effect in vitro on complement-mediated cytotoxicity of white cells and it has been demonstrated to clear almost all passenger leukocytes from donor kidneys before transplant. Anti-CD45 Mabs have been made under cGMP conditions at the Therapeutic Antibody Center at Oxford and at Baylor College of Medicine and will pass the safety tests required by the FDA.