Peroxidase arthritis. II. Lymphoid cell-endothelial interactions during a developing immunologic inflammatory response.

The interaction of lymphoid cells with vascular endothelium was studied during the development of immunologic synovitis in response to repeated intraarticular injections of a heterologous protein antigen. Lymphoid cells emigrated in venules and small veins, both by penetrating the endothelial cytoplasm and by traversing intercellular junctions. Frequent endothelial mitoses were coincident with lymphoid cell emigration. Endothelial cells in the involved vessels increased in number and bulged prominently into the vascular lumen. Endothelial nuclei contained dispersed chromatin and prominent nucleoli; the cytoplasm contained many vacuoles and abundant polyribosomes and rough-surfaced endoplasmic reticulum. Intercellular junctions were numerous and complex. These phenomena were prominent in rabbits studied after 12 to 16 daily injections; they then receded, despite continued antigenic stimulation. In animals studied after 35 or 37 daily injections, the venules appeared relatively normal, and lymphoid cell emigration was observed infrequently. Growth of new vessels was prominent at this stage. The present data do not establish whether the endothelial changes were the cause or the result of lymphoid cell emigration, although the latter seems more likely. Further studies are needed to elucidate the exact nature of these interactions.