ULTRASTRUCTURE AND CYTOCHEMICAL STAINING CHARACTERISTICS OF CANINE NATURAL-KILLER-CELLS

Background: The purpose of this work was to describe the ultrastructur e and cytochemical staining characteristics of canine peripheral blood lymphocytes with natural killer (NK) cell activity, with comparison m ade to non-NK lymphocytes. Methods: Canine lymphocyte populations eval uated for ultrastructure, cytochemical staining, and NK function (by ( 51)chromium release assay) included: peripheral blood lymphocytes; lym phocytes from band 1 (NK-enriched), band 2, and the pellet of a 45/50% percoll gradient; lymphocytes from the supernatant fluid (non-conjuga ted lymphocytes) and pellet (lymphocytes conjugated to tumor cell targ ets) of a 17% percoll gradient; and null (CD4(-)CD8(-)) and CD4(-)CD8( +) lymphocytes. Results: NK activity was concentrated in band 1 lympho cytes of the 45/50% percoll gradient with further enhancement of activ ity occurring in sorted null cells, Canine NK cells were 5.5 to 6.5 mu m in diameter with a reniform (kidney bean shape) nucleus, and electr on-dense cytoplasmic granules, NK cells (percoll band 1 cells and null cells) had larger cell and nuclear area, and less round nuclei when c ompared to non-NK lymphocytes, The overall cytochemical staining (chlo racetate esterase, peroxidase, sudan black B, naphthyl acetate esteras e, naphthyl butyrate esterase periodic acid-Schiff stain, and acid pho sphatase with and without tartrate) pattern was similar in all the lym phocyte populations evaluated, Conclusions: This work confirms the use fulness of a 45/50% percoll gradient in obtaining a NK-enriched fracti on of canine lymphocytes, and shows further enhancement of NK activity in sorted CD4(-)CD8(-) cells. The ultrastructure of canine NK cells i s similar to that reported for human NK cells, but is different from t hat of other canine peripheral blood lymphocytes. Standard cytochemica l staining does not discriminate canine NK cells from other lymphocyte s. (C) 1995 Wiley-Liss, Inc.