Cold Precipitable Haemagglutinating Factor in Serum from patients with Rheumatoid Arthritis

Abstract
Rheumatoid arthritis serum diluted 1:14 with distilled water gives a precipitate on standing for 48 hours at 4[degree]C. The sheep cell hemagglutinating factor is associated with gamma globulin in this precipitate, while similar precipitates from sera of patients with other collagen diseases do not contain the factor. It is inhibited by rabbit antiserum. A material with similar properties may be recovered from the filtrate from non-hemolytic cocci grown on a medium with a collagen base. It is suggested that it appears on the patient''s serum as a result of enzymic action on collagen tissue.