Changes in the medulla of the parathymic lymph nodes of the rat during acute gastro-intestinal inflammation.

The changes occurring in the medullary sinus and medullary cord of the parathymic lymph nodes were studied in rats after performing a small intestinal anastomosis. Polymorphonuclear leucocytes and eosinophils were phagocytosed by the macrophages of the medullary sinus. The sinus macrophages stained strongly for acid phosphatase and weakly for non-specific esterase. The medullary sinus macrophages were most numerous near the subcapsular sinus. After a small intestinal anastomosis the sinus macrophages increased in size and in number. The macrophages of the medullary cord differed from those of the medullary sinus both histochemically and ultrastructurally. The cord macrophages stained weakly for acid phosphatase, stained strongly for non-specific esterase and phagocytosed plasma cells, particularly in those specimens 2 and 5 days after the intestinal anastomosis. There was an initial significant decrease in IgA plasma cells at 2 days after the anastomosis but a subsequent increase in IgG and IgM plasma cells. The increase in IgM plasma cells preceded that of the other plasma cells.