Morphological studies of effector cell-microvessel interactions in adoptive immunotherapy in tumor-bearing animals

Murine lymphokine-activated natural killer (A-NK) cells are able to migrate to and accumulate in tumor metastases. However, the exact migratory pattern is as yet unknown. In the present study, we have investigated the migration from the vasculature towards malignant tissues of various effector cells. Our results indicate that murine A-NK cells seem to be arrested for an extended period of time in the microvasculature and also, although infrequently, to adhere to the endothelial lining of larger vessels close to tumor tissues before extravasation. While murine T lymphokine-activated killer and rat A-NK cells accumulate significantly in the subendothelial areas of larger venules in normal tissues, no such accumulation is observed with respect to murine A-NK cells. Electron microscopy reveals that the murine A-NK cells undergo an extreme deformation during extravasation and tumor infiltration. Furthermore, the cells are shown to be in an activated stage probably facilitating their migration, and hence, the elimination of tumor cells.