Autoantibodies against granulocyte-macrophage colony stimulating factor and interleukin-3 are rare in patients with Felty's syndrome.
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.
Hellmich
B
B
Poliklinik fur Rheumatologie, Universitatsklinikum Schleswig-Holstein, Campus Lubeck, Ratzeburger Allee 160, 23538 Lubeck, Germany. hellmich@rheuma-zentrum.de
Ciaglo
A
A
Schatz
H
H
Coakley
G
G
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
D001323:Autoantibodies; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D007377:Interleukin-3; D016178:Granulocyte-Macrophage Colony-Stimulating Factor