Permeability of human synovial membrane to plasma proteins. Relationship to molecular size and inflammation

Abstract Passage of plasma proteins from blood into synovial fluid was found quantitatively related to molecular size and to degree of inflammation in four groups of patients differing in severity of synovial inflammation, and in a group of autopsied subjects without joint disease. Greater inflammation was accompanied by augmented passage of each protein across the synovial membrane, and by proportionately greater increase in permeability to larger proteins. In classic rheumatoid arthritis, synovial IgM and IgG concentrations were higher than predicted from the above‐described interrelationships, suggesting local immunoglobulin synthesis.