Specificity of antibodies in rheumatoid arthritis. I. A controlled study of humoral antibodies to bovine nasal cartilage components.

Rheumatoid arthritis (RA) sera were compared in a matched, controlled study to non-RA sera for their ability to react in ELISA with antigen preparations extracted from bovine nasal cartilage. Antibodies to matrix proteins, proteoglycans and whole extract were significantly higher in RA sera than in non-RA with the reactivity for matrix proteins giving the largest difference. There was no significant difference between RA and non-RA antibody levels for collagen and collagen alpha chains. By SDS-PAGE, large pore composite gel electrophoresis, and uronic acid analysis, the matrix protein fraction contained 8 major proteins as well as two electrophoretic species of low density proteoglycans distinct from the major high density cartilage proteoglycans. Further fractionation provided a proteoglycan-free preparation containing six major proteins of 66-13 kd with which the RA sera were still highly reactive.