Kinetics and characterization of cellular responses in the peritoneal cavity of mice infected with Taenia crassiceps

Changes in the leukocyte population of the peritoneal cavity ensue immediat ely after infection with Taenia crassiceps metacestodes. Basophils and neut rophils decrease, whereas macrophages, monocytes, and lymphocytes increase to reach only modest levels by 6 wk and then diminish to nearly disappear b y 15 wk when the parasite begins rapid reproduction. Eosinophils also appea r early in infection, but then abate to lower levels that persist. In late infections, when the mass of cysticerci equals that of the mouse, the cysti cerci grow among surprisingly few inflammatory cells. Mingling with the per itoneal inflammatory cells is a number of odd-looking cells that could corr espond to the metaplasic mesothelial cells of the host or be of parasite or igin. These cells are multinucleated, they aggregate in varigerated cluster s, and form cystic structures in vitro; they also bind specific anti-T. cra ssiceps antibodies and specific T. crassiceps DNA probes in their nuclei. W hen the peritoneal cell exudate is reinjected intraperitoneally into naive mice, the odd-looking cells subsist for months, inducing in the host the sy nthesis of specific anti-ir. crassiceps antibodies and immune resistance to challenge but do not reassemble into cysticerci even after 6 mo of inocula tion. The early appearance and the immunogenic and antigenic properties of these odd-looking cells suggest they are important protagonists in the earl y host-parasite confrontation when the outcome of infection is set.