Intraperitoneal murine alveolar hydatidosis: relationship between the size of the larval cyst mass, immigrant inflammatory cells, splenomegaly and thymus involution.

Both phagocytic and nonphagocytic inflammatory cells infiltrate the peritoneal cavity of mice infected intraperitoneally with Echinococcus multilocularis cysts. A longitudinal study on the kinetics of peritoneal leukocytosis at 3 days, 1, 2, 3, 4, 6, 8, 10 and 14 weeks postinfection revealed that the restrictive and progressive growth phases of the alveolar hydatid cyst correspond sharply with the increasing and decreasing levels of peritoneal cells, respectively. The restrictive phase is characterized by the progressive peritoneal accumulation of lymphocytes, monocytoid cells and eosinophils. Between 6 and 14 weeks p.i., the alveolar cyst increased in weight 30 fold. This phase was associated with peritoneal neutrophilia, splenomegaly, involution of the thymus and a significant decline in the extravasated lymphocytes, monocytoid cells and eosinophils. These results in conjunction with our previous studies indicate that host's hydatid immunosurveillance is compromised as a result of profound immunopathologic disorders during the progressive growth phase of the alveolar cyst. In order to understand the prolonged survival of alveolar cyst, further investigation of inflammatory cell-cyst interactions is indicated.