Rabbit-immunoglobulin 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 mg/mL before HSCT ran a very low risk of developing acute GVHD grades II-IV, as compared to those with levels <70 mg/mL (11% vs. 48%, p=0.006). INTERPRETATION 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.