Correlation between canine NK cell mediated cytotoxicity and radical production

Comparison of Phenotypic and Functional Characteristics Between Canine Non-B, Non-T Natural Killer Lymphocytes and CD3+CD5dimCD21- Cytotoxic Large Granular Lymphocytes

Natural killer (NK) cells play a pivotal role in the immune response against infections and malignant transformation, and adopted transfer of NK cells is thought to be a promising therapeutic approach for cancer patients. Previous reports describing the phenotypic features of canine NK cells have produced inconsistent results. Canine NK cells are still defined as non-B and non-T (CD3⁻CD21⁻) large granular lymphocytes. However, a few reports have demonstrated that canine NK cells share the phenotypic characteristics of T lymphocytes, and that CD3⁺CD5^dimCD21⁻ lymphocytes are putative canine NK cells. Based on our previous reports, we hypothesized that phenotypic modulation could occur between these two populations during activation. In this study, we investigated the phenotypic and functional differences between CD3⁺CD5^dimCD21⁻ (cytotoxic large granular lymphocytes) and CD3⁻CD5⁻CD21⁻ NK lymphocytes before and after culture of peripheral blood mononuclear cells isolated from normal dogs. The results of this study show that CD3⁺CD5^dimCD21⁻ lymphocytes can be differentiated into non-B, non-T NK (CD3⁻CD5⁻CD21⁻TCRαβ⁻TCRγδ⁻GranzymeB⁺) lymphocytes through phenotypic modulation in response to cytokine stimulation. In vitro studies of purified CD3⁺CD5^dimCD21⁻ cells showed that CD3⁻CD5⁻CD21⁻ cells are derived from CD3⁺CD5^dimCD21⁻ cells through phenotypic modulation. CD3⁺CD5^dimCD21⁻ cells share more NK cell functional characteristics compared with CD3⁻CD5⁻CD21⁻ cells, including the expression of T-box transcription factors (Eomes, T-bet), the production of granzyme B and interferon-γ, and the expression of NK cell-related molecular receptors such as NKG2D and NKp30. In conclusion, the results of this study suggest that CD3⁺CD5^dimCD21⁻ and CD3⁻CD5⁻CD21⁻ cells both contain a subset of putative NK cells, and the difference between the two populations may be due to the degree of maturation.

Immunological Effects of Recombinant Feline Interferon-ω (KT-80) Administration in the Dog

The immunological effects of recombinant feline interferon-omega (rFeIFN-omega ; KT-80, Toray) were examined on administration to healthy dogs. The activities of whole blood cells, macrophages, and natural killer cells were enhanced. Moreover, the whole blood activity was examined when KT-80 was administered to dogs which had been diagnosed as having natural canine parvovirus (CPV) infection. Only some cases in which the activity increased until 3 hr post-administration survived. These results suggest that rFeIFN-omega (KT-80) treatment enhanced the cellular immunity of normal dogs, and could exert significant therapeutic effects on only natural CPV infected dogs with induced continuous immunoenhancement.

Clinical, hematologic, and immunophenotypic characterization of canine large granular lymphocytosis

Clinical, hematologic, and immunophenotypic data were studied in 25 dogs with large granular lymphocyte (LGL) lymphocytosis. Primarily large-breed dogs were affected, with an average age at initial diagnosis of 10 years (range 5-14 years). All dogs had persistent (>4 months) LGL lymphocytosis except for three that were euthanized with aggressive disease. Splenomegaly was reported in 12 of 20 dogs in which splenic size was evaluated. The clinical course was heterogeneous and dogs were divided into four groups based on similar clinical and hematologic findings: acute leukemia (3/25), persistent lymphocytosis with anemia (12/25), persistent lymphocytosis without anemia (8/25), and reactive lymphocytosis (2/25). Immunophenotypes varied within groups but were homogeneous among cells from the same patient except in the two dogs classified as reactive LGL lymphocytosis. Analysis of T-cell receptor (TCR) usage identified three main LGL lineages. TCRalphabeta was expressed in 15/25 (60%) cases. TCRgammadelta was expressed in 8/25 (32%) cases, and 2/25 (8%) cases were CD3-, compatible with NK cells. beta2 integrin expression was distinctive. CD11a was consistently expressed, while CD11b was absent. CD11c was expressed only weakly in 16/25 (64%) cases. The leukointegrin alphadbeta2 was highly prevalent on all LGL lineages, being expressed in 23/25 (92%) cases. Prominent involvement of the spleen, relative sparing of bone marrow, an unexpectedly large proportion of gammadelta T-cell LGLs, and the distinctive beta2 integrin expression pattern on diverse lineages of LGLs suggest the disease arises from unique populations of lymphocytes that preferentially localize in the splenic red pulp.

Active-oxygen involvement in canine NK-mediated cytotoxicity

We examined the relationship between natural killer (NK) cell-mediated cytotoxicity, the produced active-oxygen and cytotoxic factor (CF) release in co-culturing canine NK cells with tumor cells (CL-1 target cells). In co-culturing, the adding of n-propyl gallate (active-oxide scavenger) removed the produced active-oxygen, which inhibited NK cell-mediated cytotoxicity and the CF release. Moreover, adding of this agent inhibited the tyrosine phosphorylation of NK intracellular protein which observed in co-culturing. Therefore, the active-oxygen produced from canine NK cells are thought to relate the signal transduction in NK-mediated cytotoxicity.

Relationship between radical production and natural killer cytotoxic factor (NKCF) in canine natural killer (NK) cell-mediated cytotoxicity

The relationship between radical production and natural killer cytotoxic factor (NKCF) release via canine natural killer (NK)-mediated cytotoxic mechanism was examined. Radical production and NKCF release was induced in NK cells stimulated with either dead target cells, or their cytoplasmic membranes, as well as live target cells. Canine NKCF evoked target cell lysis but did not induce radical production. Radical production was inhibited by the addition of Tiron or n-propyl gallate, whereas NK-mediated cytotoxicity and NKCF release were only inhibited by the addition of n-propyl gallate. These results suggested that radical production and NKCF release may be induced by the contact and binding of NK cells to the target cell cytoplasmic membrane. Therefore, the release of NKCF from NK cells attached to the target cell cytoplasmic membrane may be associated with the production of radicals, especially hydroxyl radicals.

Characterization of natural killer cytotoxic factor (NKCF) from canine NK cells

We investigated the presence of canine natural killer cytotoxic factor (NKCF). Canine natural killer (NK) cell-mediated cytotoxicity measured by 51chromium (51Cr) release assay was found to be highest in the T-cell population, which was fractionated into the 35-40% Percoll fraction by discontinuous gradient centrifugation. The cytotoxicity of NKCF in the culture supernatant showed a similar tendency to NK activity. Release of NKCF was rapid after contact with target cells, and reached a plateau in 60 min. The cytotoxicity of NKCF could be detected within at least 15 min in coculture with CL-1 target cells, reaching a plateau in 60 min. We also characterized canine NKCF and found it to be a protein, which was stable against both heat and cold treatment. These findings suggest that canine NK cells release NKCF immediately after recognition and binding to the target cell, and that NKCF plays an important role in canine NK-mediated cytotoxicity.