Trichinella spiralis: killing of newborn larvae by lung cells

The migratory stage of Trichinella spiralis, the newborn larva (NBL), travels along the pulmonary microvascular system on its way to the skeletal muscle cells. The present work studies the capability of lung cells to kill NBL. For this purpose, in vitro cytotoxicity assays were performed using NBL, lung cell suspensions from Wistar rats, rat anti-NBL surface sera, and fresh serum as complement source. The cytotoxic activity of lung cells from rats infected on day 6 p.i. was compared with that from noninfected rats. Two and 20 h-old NBL (NBL2 and NBL20) were used as they had shown to exhibit different surface antigens altering their biological activity. Sera antibodies were analyzed by indirect immunofluorescence assay, and cell populations used in each assay were characterized by histological staining. The role of IgE in the cytotoxic attack against NBL was analyzed using heated serum. The FcεRI expression on cell suspensions was examined by flow cytometry. Results showed that lung cells were capable of killing NBL by antibody-dependent cell-mediated cytotoxicity (ADCC). Lung cells from infected animals yielded the highest mortality percentages of NBL, with NBL20 being the most susceptible to such attack. IgE yielded a critical role in the cytotoxic attack. Regarding the analysis of cell suspensions, cells from infected rats showed an increase in the percentage of eosinophils, neutrophils, and the number of cells expressing the FcεRI receptor. We conclude that lung cells are capable of killing NBL in the presence of specific antibodies, supporting the idea that the lung is one of the sites where the NBL death occurs due to ADCC.