Natural killer (NK) cells in domestic animals: phenotype, target cell specificity and cytokine regulation

A comprehensive review of NK cells in animals of veterinary medical importance has not been previously published. However, these cells have a high level of immunological/medical relevance due to their role in tumour cell destruction and B-cell regulation, as well as their inhibitory activities against various parasites and bacteria. In the present review, NK cells from agriculturally important animals are characterized. Cell phenotype descriptions have shown that for each species, unique (i.e. non-cross-reactive with anti-human CD antibodies) and different monoclonals are required to identify NK cells. These cells lyse certain tumour and virus transformed target cells and, as might be expected from the diverse species compared in this review, analysis of the tissue distribution of NK cells gives highly varied results. NK cell morphology differs in these species from small agranular to large granular lymphocytes. The final area considered relates to studies on the effects of cytokines on NK function and to research identifying which cytokines (if any) are produced by NK cells during activation responses. The largest quantity of available data concerns functional and descriptive studies in these animals. However, it is appropriate to consider this research as a starting point on which to build comparative and molecular studies of the roles of NK cells in immunosurveillance and immunoregulation.