No abstract

We have previously demonstrated that during pregnancy there exists an increased parasiticide activity against Trichinella spiralis newborn larvae (NBL) in infected rats. In this work we analysed the contribution of peritoneal cells from noninfected pregnant rats to the mortality of the NBL in cytotoxicity assays, and evaluated the role of progesterone in this effector mechanism. Our findings suggest that progesterone can induce activation of effector peritoneal cells to destroy the NBL in a rapid and antibody-independent manner. The administration of progesterone to ovariectomized rats also led to a significant decrease in the parasite load of the animals, thus demonstrating that progesterone induces the increase of the parasiticide activity of the leukocytes involved in the mechanisms of NBL death.

The ability of human eosinophils to kill the newborn larvae (NBL) of Trichinella spiralis of different maturation status, in the presence of antibody, was studied. A cytotoxic in vitro test was performed using NBL less than 2 h of age (NBL2) or NBL maintained in culture at 37 degrees C for 20 h (NBL20), peripheral blood eosinophils, anti-Trichinella serum and human fresh serum as source of complement. Under these experimental conditions eosinophils from normal individuals attached to NBL2 as well as to NBL20 but only the latter were killed. On the other hand, eosinophils from volunteers with eosinophilia killed NBL regardless of larval age. Neither adherence nor significant mortality was observed in the absence of immune serum. These results indicate that NBL maturation and eosinophil activation status are crucial for antibody-dependent cellular cytotoxic reaction (ADCC).