Natural Cell-Mediated Cytotoxicity in Guinea Pigs: Properties and Specificity of Natural Killer Cells

Abstract

Abstract Lymphoid cells of guinea pigs were found to be naturally cytotoxic against a variety of target cells. Natural killer (NK) cell activity was high in peripheral blood and spleen, low in lymph nodes and peritoneal exudates, and absent in the thymus. Significant activity was found between the ages of 3 and 40 weeks, and strain 2 guinea pigs had a higher NK activity than strain 13 guinea pigs. Peripheral blood NK cells were sensitive to treatment with ammonium chloride solution, whereas splenic NK cells were resistant to the same treatment. The NK cells were found to be nonadherent to nylon wool and plastic and were enriched among cells bearing receptors for the Fc portion of IgG. The NK activity of guinea pig lymphocytes was selective in that only some, but not all, of the target cells used were susceptible to the cytotoxic effector cells. Susceptible target cells included syngeneic, allogeneic, and xenogeneic tumor cell lines, especially the human myeloid cell line K562, and some passages of primary syngeneic fibroblast cultures. A positive correlation was found between the direct susceptibility of different targets to NK cells and their ability to inhibit competitively the killing of K562 target cells. The NK cells in guinea pigs appear to be similar to human NK cells in several aspects and may, therefore, serve as a useful model for studying certain aspects of human NK activity.