title: Autoantibodies against granulocyte-macrophage colony stimulating factor and interleukin-3 are rare in patients with Felty's syndrome.
abstract: OBJECTIVE
  Antibodies against granulocyte colony stimulating factor are frequently found in patients with Felty's syndrome (FS). In this study, we examined the prevalence of antibodies against two other granulopoietic cytokines: granulocyte-macrophage colony stimulating factor (GM-CSF) and interleukin-3 (IL3).
  
  
  METHODS
  Sera of 32 patients with FS, 20 normocytic patients with rheumatoid arthritis (RA), and 72 healthy individuals were screened for the presence of antibodies against GM-CSF and IL3 by ELISA and bioassays, using the human erythroleukaemia cell line TF-1.
  
  
  RESULTS
  In two of the 32 patients with FS, antibodies to GM-CSF and IL3 were detectable by ELISA. Binding anti-GM-CSF antibodies were also detected in one of the 72 healthy controls, while in another healthy subject and in one of the patients with normocytic RA, anti-IL3 antibodies were present. Serum from one of the two patients with FS who tested positive for anti-IL3 and anti-GM-CSF antibodies by ELISA showed strong neutralising capacity to the biological effect of IL3, but not to GM-CSF in vitro. Patients with FS had significantly higher serum levels of GM-CSF (median; 2.82 pg/mL; interquartile range 2.64-3.19 pg/mL) compared with patients with RA (2.52 pg/mL; 2.28-2.72 pg/mL; p = 0.012) and healthy controls (2.23 pg/mL; 2.04-2.52; p<0.001). In addition, serum levels of IL3 in patients were significantly higher in FS (10.05 pg/mL; 8.94-11.98) compared with controls (4.79 pg/mL; 3.72-7.22; p<0.001), but not compared with RA patients (9.52 pg/mL; 8.32-10.42; p = 0.17).
  
  
  CONCLUSIONS
  Antibodies to GM-CSF and IL3 are rare in patients with FS and RA and in healthy subjects. In individual patients with FS, the presence of neutralising anti-IL3 antibodies may contribute to the development of cytopenia.
authors.affiliation: Poliklinik fur Rheumatologie, Universitatsklinikum Schleswig-Holstein, Campus Lubeck, Ratzeburger Allee 160, 23538 Lubeck, Germany. hellmich@rheuma-zentrum.de
authors.forename: B
authors.initials: B
authors.lastname: Hellmich
authors.forename: A
authors.initials: A
authors.lastname: Ciaglo
authors.forename: H
authors.initials: H
authors.lastname: Schatz
authors.forename: G
authors.initials: G
authors.lastname: Coakley
mesh_terms: D001323:Autoantibodies / Q000097:blood*; D016022:Case-Control Studies; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005258:Felty Syndrome / Q000276:immunology*; D005260:Female; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000276:immunology*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D007377:Interleukin-3 / Q000276:immunology*; D008297:Male; D008875:Middle Aged
chemical_list: D001323:Autoantibodies; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D007377:Interleukin-3; D016178:Granulocyte-Macrophage Colony-Stimulating Factor