Arthus Synovitis with Horseradish Peroxidase as Antigen: Sequential Participation of Platelets and Leucocytes

摘要

Direct, active Arthus reactions in response to horseradish peroxidase were studied in the synovial membranes of rabbits. In tissues examined 15 to 30 minutes after antigen injection, immune precipitates were prominent in and about the superficial capillaries. Those within the lumen often lacked peroxidase activity, suggesting that they were formed in antibody excess. In contrast, precipitates within the vessel walls and in the interstitial tissues possessed peroxidase activity, probably reflecting the presence of a greater proportion of antigen. Intraluminal precipitates were associated with aggregated platelets, some of which were degranulated. Junctional gaps between endothelial cells were frequent in the involved vessels. At intervals of one to 6 hours after antigen injection, continued deposition of immune precipitates was associated with emigration of polymorphonuclear leucocytes, thrombosis and haemorrhage. In contrast to the events observed at early intervals, these phenomena were most prominent in the deeper subsynovial venules. Early increased vascular permeability associated with immunologically mediated degranulation of platelets appears to facilitate the development of Arthus vasculitis in this system.