Assessment of antibody-independent cellular cytotoxicity (AICC) of porcineneutrophilic granulocytes by quantitative flow cytometry. Lack of modulation by larval products of Oesophagostomum dentatum

After infection of pigs by the larvae of Oesophagostomum dentatum, granulom as are formed around the third-stage larvae in the submucosa of the gut whi ch contain a considerable number of neutrophils. This has no obvious impact on the larvae, which develop to fourth-stage larvae within these granuloma s. We therefore asked, whether the products of O. dentatum larvae modulate the functional capacity of porcine neutrophils. The antibody-independent ce llular cytotoxicity (AICC) was chosen as a model system. This assay was dev eloped for the pig and quantified using flow cytometry. Bovine lymphoblasto id cells (cell line Anna TA1) served as targets. The measurement of cytotox icity was based on the determination of absolute numbers of vital target ce lls. This procedure proved to be reliable and required no additional labell ing of target and/or effector cells. Porcine neutrophils, when stimulated w ith phorbol 12-myristate 13-acetate (PMA; greater than or equal to 10 nmol/ l), killed target cells at effector:target ratios between 1 : 1 and 9 : 1. AICC was not demonstrable after 4 h but could be observed between 16 h and 20 h after in vitro co-culture. Killing of targets required close physical contact between effector and targets, since supernatants of PMA-stimulated polymorphonuclear cells were not able to lyse the target cells. Homogenates of third- and fourth-stage larvae of O. dentatum did not affect the vitali ty of porcine granulocytes or target cells in vitro, nor did they modulate the AICC capacity of porcine granulocytes.