Natural killer cell activity in adult gnotobiotic dogs.

An in vitro assay for natural killer cell activity by canine peripheral blood leukocytes was developed, using chromium-51-labeled heterologous (Vero) and homologous (Madin-Darby canine kidney, canine melanoma, and canine thyroid adenocarcinoma) target cells. Transformed tumor cell lines proved highly susceptible to natural killer-mediated lysis. Leukocytes from adult gnotobiotic dogs possessed levels of activity comparable to that observed in conventional animals.