Pathogenesis and host response in subcutaneous alveolar hydatidosis. II. Intense plasmacellular infiltration in the paracortex of draining lymph nodes.

Male C57L/J mice were infected subcutaneously in the left flank with 10 cysts of Echinococcus multilocularis. The draining and contralateral nodes were excised at weekly intervals, weighed, and examined histologically. Lymphoproliferation occurred in both the follicles and the paracortex (PCA) of the draining lymph nodes at one week postinfection (p.i.). Disorganization in the PCA of the draining nodes, was characterized by replacement of lymphocytes by plasma cells and the flattening of the endothelial cells lining the postcapillary venules. This began at three weeks p.i. and was completed by 12 weeks p.i. No comparable alterations occurred in the contralateral nodes during this period, but at 22 weeks p.i. these nodes were disorganized and histologically identical to the draining nodes. The growth and histogenesis of the subcutaneous alveolar cysts correlated with the expansion and disorganization of the PCA. The regulation of subcutaneous murine alveolar hydatidosis is discussed with reference to immune-deviation which is brought about by the antigenic load and plasmacellular infiltration in the draining lymph nodes.