Rabbit-immimoglobulin G levels in patients receiving thymoglobulin as part of conditioning before unrelated donor stem cell transplantation

Abstract

Background and Objectives. The role of serum concentrations of rabbit antithymoglobulin (ATG) in the development of acute graft-versus-host disease (GVHD) after allogeneic hematopoietic stem cell transplantation (HSCT) with unrelated donors is unknown. Design and Methods. We determined the serum concentration of rabbit immunoglobulin-G (IgG) using an enzyme linked immunosorbent assay in 61 patients after unrelated donor HSCT. The doses of ATG ranged between 4 and 10 mg/kg. The conditioning consisted mainly of cyclophosphamide and total body irradiation or busulfan. Most patients received GVHD prophylaxis with cyclosporine and methotrexate. Results. The rabbit IgG levels varied widely in each dose group. The levels of rabbit IgG gradually declined and could still be detected up to five weeks after HSCT. We found a correlation between the grade of acute GVHD and the concentration of rabbit IgG in serum before the transplantation (p=0.017). Patients with serum levels of rabbit IgG >70 μg/mL before HSCT ran a very low risk of developing acute GVHD grades II-IV, as compared to those with levels <70 μg/mL (11% vs. 48%, p=0.006). Interpretations and Conclusions. The measurement of rabbit IgG levels in patients receiving ATG as prophylaxis against GVHD after HSCT may be of value in lowering the risk of severe GVHD. ©2005 Ferrata Storti Foundation.