IMMUNE CHARACTERIZATION OF PERIPHERAL BLOOD MONONUCLEAR CELLS OF THE DOGS RESTORED FROM INOCULATION OF CANINE TRANSMISSIBLE VENEREAL TUMOR CELLS

Abstract

Canine transmissible venereal tumor (CTVT) is a tumor which can be transmitted naturally through mucosa contact between dogs. When CTVT cells are experimentally inoculated on dogs, they will grow rapidly (Progressive/P phase) and then regress (Regressive/R phase) spontaneously. Therefore, it is a good model to investigate the interactions between tumor cells and host immune system. Previous studies have shown that CTVT cells cannot grow in the dogs restored from CTVT inoculation. To investigate the possible mechanism, this study characterized the CTVT-specific immune response of the peripheral blood mononuclear cells (PBMCs) which isolated from the blood of "naïve" or "CTVT-restored" dogs. The phenotypes (CD3, CD4, CD8, or CD21) of PBMCs were examined by flowcytometry. In response to CTVT stimulation, proliferation, IFN-γ secretion, and cytotoxicity of PBMCs were analyzed. Expression level of proinflammatory cytokines (TNF-α, IL-1β, IL-6, TGF-β), Th1 (IL-2, IFN-γ), and Th2 cytokines (IL-4, IL-10) and cytotoxic proteins (Granzyme B, Perforin) in PBMCs was also evaluated by real-time RT-PCR. The results indicated that there is no significant difference between two groups on lymphocyte phenotypes. Proliferation, IFN-γ secretion, and cytotoxicity of PBMCs between two groups showed no significant difference, except naïve PBMCs present higher proliferation after Con-A stimulation. Production of IL-1β and IL-6 in naïve PBMCs was higher than that in CTVT-restored PBMCs (p < 0.05). The production difference of IL-1β and IL-6 between two groups might be the reason why CTVT cannot be reinoculated on CTVT-restored dog. However, further investigations are necessary to explore the exact role of these cytokines in CTVT growth.