Antibodies to glycosylphosphatidyl-inositol anchored proteins (GPI-AP) in antithymocyte and antilymphocyte globulin: possible role for the expansion of GPI-AP deficient cells in aplastic anemia

Heike H. Breitinger (1) , Markus T. Rojewski (1) , Hubert Schrezenmeier (1)

1 Institut für Transfusionsmedizin

Antithymocyte globulin (ATG) and antilymphocyte globulin (ALG) are currently used successfully for immunosuppressive treatment of aplastic anemia. In this study we have investigated whether commercial ATG/ALG preparations contain antibodies against glycosylphosphatidyl-inositol anchored proteins (GPI-AP), which could be responsible for emergence of GPI-deficient populations in aplastic anemia after ATG/ALG therapy. We analyzed four commercial ATG/ALG preparations by competitive binding assays using flow cytometry. Quantification was achieved by calculating the concentration of ATG/ALG required to give 50% inhibition of binding the specific fluorochrome-labeled monoclonal antibody (EC50). High concentrations of antibodies against the GPI-anchored protein CD52 were found in all preparations (Lymphoglobulin® Genzyme, Thymoglobulin® Genzyme, ® Pharmacia & Upjohn, and ATG-Fresenius S Fresenius). Antibodies against the GPI-anchored protein CD48 are present in significant concentrations except in the preparation ®. CD16 antibodies were found in lower concentrations. We could not detect significant concentrations of antibodies against the GPI-anchored proteins CD157 and CD14. Campath-1H, a monoclonal antibody against the GPI-anchored protein CD52, has been used as immunosuppressive tool for T-cell depletion. CD52 antibodies in ATG/ALG preparations might contribute in the same way to the immunosuppressive effects in treatment of aplastic anemia. It is known that in a substantial proportion of patients with aplastic anemia GPI-deficient cells are present in a low level at diagnosis or emerge after immunosuppressive therapy. GPI-anchored antibodies in ATG/ALG preparations might lead to a relative advantage for pre-existing GPI-deficient cells caused by an escape from the antibody-mediated attack.

Mots clés: Glycosylphosphatidyl-inositol anchored proteins; Antithymocyte globulin; Antilymphocyte globulin; Aplastic anemia; Immunosuppression

Heike H. Breitinger, Markus T. Rojewski, Hubert Schrezenmeier. Antibodies to glycosylphosphatidyl-inositol anchored proteins (GPI-AP) in antithymocyte and antilymphocyte globulin: possible role for the expansion of GPI-AP deficient cells in aplastic anemia. Annals of Hematology, 2009, 88 (9), pp.889-895. ⟨10.1007/s00277-008-0688-0⟩. ⟨hal-00535024⟩