Type III collagen: A major constituent of rheumatoid and normal human synovial membrane

The findings establish that type III collagen is a major constituent of grossly proliferated rheumatoid and normal synovium. Unlike the collagen of normal synovium most of that in rheumatoid tissue could be solubilised by pepsin at 4 degrees C. Moore than half the pepsin-solubilised collage was identified as type III, the remainder being type I, by CM-cellulose chromatography; SDS-polyacrylamide electrophoresis with and without reduction of disulphide bonds; and amino acid analysis. Moreover, at least half the total collagen in several samples of normal as well as rheumatoid tissue was clearly type III when cyanogen bromide-derived peptides were run on SDS-polyacrylamide electrophoresis and compared with peptides prepared from purified types I and III collagens. This conclusion was supported by the isolation on phosphocellulose and quantitation by amino acid analysis of the collagen peptides alpha(1)CB2 and alpha(III)CB2 from a cyanogen bromide digest of rheumatoid synovium.