Rheumatoid factor isotypes and anti-agalactosyl IgG antibodies in systemic sclerosis.
BACKGROUND: Rheumatoid factor isotypes and anti-agalactosyl IgG antibodies (anti-AG IgG) have been reported to be detected and correlated with the disease activity in some collagen diseases. OBJECTIVES: To study the frequency and the clinical significance of IgM, IgG and IgA rheumatoid factor (IgM-RF, IgG-RF and IgA-RF) and anti-AG IgG in patients with systemic sclerosis (SSc). METHODS: Seventy-nine serum samples from patients with SSc were examined by specific enzyme-linked immunosorbent assays. RESULTS: The levels of IgM-, IgG-, IgA-RF and anti-AG IgG were significantly higher in SSc patients than in normal healthy controls. The levels of IgM- and IgA-RF were significantly higher in patients with diffuse cutaneous SSc than in those with limited cutaneous SSc. IgM-, IgG- and IgA-RF and anti-AG IgG were significantly elevated in 39%, 32%, 23% and 35% of 79 SSc patients, respectively. The prevalence of pulmonary fibrosis, oesophageal involvement and cutaneous telangectasias in patients with elevated IgA-RF levels was significantly higher than in those with normal levels. The incidence of pitting scars of digits in those with elevated IgG-RF levels and the incidence of contracture of phalanges in those with elevated IgM-RF levels were significantly higher than in those with normal levels. The frequency of increased erythrocyte sedimentation rate in patients with elevated IgG-RF and the frequency of increased C-reactive protein in those with elevated IgM-RF were significantly greater than in those with normal levels. CONCLUSIONS: IgM-, IgG-, IgA-RF and anti-AG IgG can be serum indicators of specific clinical manifestations in SSc patients.