Immune killing of newborn Trichinella larvae by human leucocytes

The capacity of human leucocytes from normal donors to kill the newborn larvae of the nematode Trichinella spiralis in vitro, in the presence of serum from infected individuals, was studied using newborn larvae (NBL) less than 2 h of age or NBL that had been maintained in culture at 37 degrees C for 20 h. Neutrophils and monocytes attached to newborn Trichinella larvae and killed them, regardless of their age. When eosinophils were used, 20 h old NBL were killed whereas 2 h old NBL were not. Complement was essential in the cytotoxic effect of leucocytes. These results indicate that host defence against T. spiralis in humans may be a complex mechanism in which different cell types can be involved. They also show that the age of maturation of the NBL is of paramount importance in the antibody-dependent cellular cytotoxicity reaction.