Pathological changes in the lymphoreticular tissues of Swiss mice infected with Echinococcus granulosus cysts.

Swiss mice infected intraperitoneally with approximately 1,500 protoscolices of Echinococcus granulosus and sacrificed at three and 13 months post infection yielded both viable and degenerated hydatid cysts. The mean cyst weights in the three and 13 months post infected mice were 0.13 and 2.1 g, respectively. Sections of spleens and lymph nodes in the three months post infected mice showed hyperplastic follicles and blastoid cells in thymus dependent areas. At 13 months post infection T cells from paracortex and periarterial areas were replaced by plasma cells and confluent sheets of histiocytes; follicles had retained germinal centres and medullary areas showed intense plasmacytosis and sinus histiocytosis. Failure of mice to control the histogenesis of hydatid cyst with reference to numerical reduction in T cells is discussed.