Humoral response to sheep red blood cells in C57L/J mice during early and chronic stages of infection with Echinococcus multilocularis cysts.

C57L/J male mice infected with Echinococcus multilocularis cysts were challenged intraperitoneally at 4, 8, and 12 weeks postinfection (p.i.) with 3 x 10(9) sheep erythrocytes. The direct plaque forming cells, 2-mercaptoethanol (2-ME) sensitive (4-day sera) and 2-ME-resistant (8-day sera) haemagglutinin responses were significantly elevated at eight and 12 weeks p.i. as compared to controls or the fourweeks postinfected mice. Possible mechanisms of immunopotentiation in the chronically infected mice is discussed in relation to the larval cyst mass, splenomegaly, and B cell hyperplasia in the lymphoid tissues during the course of infection.