title: Rabbit anti-T-lymphocyte globulin (ATG) persists with differential reactivity in patients' sera after full hematopoetic regeneration from allogeneic stem cell transplantation.
abstract: BACKGROUND
  Rabbit polyclonal anti-T-lymphocyte Globulin (ATG-F®, Fresenius) is widely used for GvHD prophylaxis in allogeneic stem cell transplantation (SCT). ATG has a wide epitope spectrum and has been shown to react with all compartments of peripheral blood mononuclear cells (PBMNCs). ATG induces apoptosis in all cellular compartments. In this study we investigated the binding of ATG in sera from ten patients treated with rabbit ATG to PBMNCs and subcellular compartments after full hematopoetic regeneration on day 21 post SCT.
  
  
  METHODS
  Sera from ten patients treated with unrelated donor allogeneic SCT for hematologic malignancy were collected after full hematopoetic regeneration on day 21 post SCT and incubated with healthy donor PBMNCs. Rabbit ATG on PBMNCs was detected by staining with fluorochrome labeled anti-rabbit IgG antibody. PBMNC compartments were investigated by counterstaining with lineage markers CD4, CD8, CD14 CD20 and CD56. Positive control was the fresh ATG preparation.
  
  
  RESULTS
  We found that patient's' sera retained activity towards PBMNCs in all patients, yet at reduced intensity. When cell compartments were analyzed we found a differential pattern of ATG reactivity within sera. The mean percentage of total cells reacting with serum ATG from ten patients compared to fresh ATG (100%) was 44% of CD4 positive and 58% of CD8 positive T-lymphocytes, 41% of CD56 positive NK-cells, 83% of CD20 positive B-lymphocytes and 98% of CD14 positive monocytes. However, inter-individual variations were high with a wide spread around the mean especially for T-lymphocytes.
  
  
  CONCLUSIONS
  We conclude that upon PBMNC regeneration following SCT and immunosuppressive treatment with ATG subpopulations of T-lymphocytes (CD4, CD8) and NK cells (CD56) are selected that lose epitopes recognized by ATG while B-lymphocytes (CD20) and monocytes (CD14) maintain a homogeneity with respect to epitopes recognized by ATG. This may be due to loss of idiotypes reacting with subpopulations of high frequency and turnover. Further studies should investigate the subphenotype of these populations and functional effects of extremely high or low reactivity with one or more compartments in some patients on GvHD and disease outcome.
authors.affiliation: National Center for Tumor Diseases, Dept. of Medical Oncology, Heidelberg University Medical Center, Im Neuenheimer Feld 460, D-69120 Heidelberg, Germany; Charité Medical Center Berlin, Dept. of Hematology and Oncology, Campus Virchow Klinik, Augustenburger Platz 1, 13353 Berlin, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Ziegler
authors.affiliation: Albert Ludwigs University Medical Center Freiburg, Dept. of Hematology and Oncology, Hugstetter Str. 55, D-79106 Freiburg, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Finke
authors.affiliation: National Center for Tumor Diseases, Dept. of Medical Oncology, Heidelberg University Medical Center, Im Neuenheimer Feld 460, D-69120 Heidelberg, Germany; Albert Ludwigs University Medical Center Freiburg, Dept. of Hematology and Oncology, Hugstetter Str. 55, D-79106 Freiburg, Germany. Electronic address: carsten.gruellich@med.uni-heidelberg.de.
authors.forename: Carsten
authors.initials: C
authors.lastname: Grüllich
mesh_terms: D000906:Antibodies / Q000097:blood*; D018951:Antigens, CD20 / Q000276:immunology; D000961:Antilymphocyte Serum / Q000097:blood / Q000276:immunology*; D017209:Apoptosis / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology; D015704:CD4 Antigens / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D019002:CD56 Antigen / Q000276:immunology; D016827:CD8 Antigens / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D000939:Epitopes / Q000276:immunology; D006086:Graft vs Host Disease / Q000628:therapy*; D006087:Graft vs Host Reaction / Q000276:immunology; D006801:Humans; D007165:Immunosuppression Therapy; D007166:Immunosuppressive Agents / Q000627:therapeutic use*; D007694:Killer Cells, Natural / Q000276:immunology; D007963:Leukocytes, Mononuclear / Q000276:immunology; D018950:Lipopolysaccharide Receptors / Q000276:immunology; D033581:Stem Cell Transplantation; D014184:Transplantation, Homologous
chemical_list: D000906:Antibodies; D018951:Antigens, CD20; D000961:Antilymphocyte Serum; D015704:CD4 Antigens; D019002:CD56 Antigen; D016827:CD8 Antigens; D000939:Epitopes; D007166:Immunosuppressive Agents; D018950:Lipopolysaccharide Receptors; C522918:NCAM1 protein, human
keywords: ATG; Peripheral blood mononuclear cell; Stem cell transplantation; Subpopulation