Using a highly sensitive Radioimmunoassay (RIA), the kinetics of synthesis of anti-
fibrillin (Fbn-1)
autoantibodies were studied in 17 patients with
mixed connective tissue disease (
MCTD) and two with
CREST syndrome calcinosis, Raynaud's oesophageal dismotility, sclerodectyly and teleangiectasis who were found to be positive for this autoimmune response.
IgG autoantibodies specific for recombinant Fbn-1 (rFbn-1) (aa 369-425) were found in all patients excepting one with
MCTD,
multiple sclerosis, and
dermatomyositis.
IgM were found in fewer cases. Several kinetics patterns of anti-Fbn-1
autoantibodies were observed: a) long lasting persistence of
IgG and
IgM autoantibodies up to 14 years; b) fluctuation of
antibodies during various periods up to 16 years; c) disappearance of antibody response after several years, and d) patients producing
IgG but not
IgM autoantibodies. No differences in the synthesis of
autoantibodies were observed between
MCTD patients with a stable disease, and those developing during the course features of
systemic sclerosis (SSc),
Sjogren's syndrome, or rheumatoid-like
arthritis. In one patient displaying a lupus-like syndrome for 3 years, the appearance of anti-Fbn-1
autoantibodies coincided with the occurrence of
MCTD and scleroderma. While the detection of anti-Fbn-1
autoantibodies may be clinically useful in differential diagnosis or eventual prognosis of patients with
connective tissue diseases, their role in the pathogenesis of scleroderma syndromes requires further investigation.