Measurement of beta-thromboglobulin connective tissue activating peptide-III platelet antigen concentrations in...

Concentrations of the human platelet proteins beta-thromboglobulin (beta-TG) and connective tissue activating peptide (CTAP)-III were measured in synovial fluid (SF) samples by radioimmunoassay of their common beta-T/CTAP antigen. beta-T/CTAP antigen concentrations were higher in rheumatoid SF than in samples from osteoarthritis patients. When concurrent SF and plasma samples were compared, SF antigen levels were weakly correlated with plasma antigen concentrations. Incubation of fresh polymorphonuclear leukocytes with antigen in SF resulted in apparent destruction of the antigen. Our study confirms the presence of a platelet-derived growth factor antigen in the pathologic joint, and suggests that leukocytes may participate in its clearance from inflamed joints.