Article Text
Abstract
Objectives: 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.
- ANC, absolute neutrophil count
- FS, Felty’s syndrome
- G-CSF, granulocyte colony stimulating factor
- GM-CSF, granulocyte−macrophage colony stimulating factor
- IL3, interleukin-3
- LGL, large granular lymphocytes
- RA, rheumatoid arthritis
- RF, rheumatoid factor
- rh, recombinant human
- Felty’s syndrome
- anti-GM-CSF antibodies
- anti-IL3 antibodies
- granulocyte−macrophage colony stimulating factor
- interleukin-3