Effect of rCaIFN-γ pretreatment on propofol-isoflurane suppression of NK cytotoxic activity in the peripheral blood of dogs.

In dogs, natural killer (NK) cell cytotoxic activity, which is an index of antitumor immunity, decreases after general anesthesia. In this study, we examined whether the decrease in NK cytotoxic activity can be controlled with interferon-gamma (IFN-γ) treatment. Beagles were divided into 2 groups: a treated group (n = 6) that received recombinant canine IFN-γ (rCaIFN-γ) and an untreated control group (n = 6). Blood samples were taken before and at 24, 120, and 192 hours after anesthesia. NK cytotoxic activity toward canine thyroid cancer cells was measured in isolated lymphocytes with the Rose Bengal assay. The decrease in NK cytotoxic activity after anesthesia was significantly inhibited by administration of rCaIFN-γ before propofol-isoflurane anesthesia. Further studies are necessary to evaluate the clinical implications of rCaIFN-γ treatment in tumor recurrence and morbidity.

Effect of rCaIFN-γ on NK cytotoxic activity in the peripheral blood of dogs.

Previously, the ability of interferon (IFN) to reinforce antitumor immune capacity has received much attention. In humans and mice, natural killer (NK) cells are activated by IFN, thereby reinforcing antitumor immunity. We investigated whether NK cytotoxic activity can be enhanced by recombinant canine interferon-gamma (rCaIFN-γ) in dogs. First, we investigated the effects of various concentrations of and time exposures to IFN-γ in the culture medium on the NK cytotoxic activity of peripheral blood lymphocyte (PBLs) extracted from healthy beagles. Time- and concentration-dependent enhancement of NK cytotoxic activity of PBLs was observed. We then investigated whether the NK cytotoxic activity of PBLs is enhanced 24h after administration of rCaIFN-γ (10,000 units/kg body weight) in healthy beagles. Our in vivo study confirmed that NK cytotoxic activity of PBLs was enhanced by this approach, suggesting that antitumor immunity was reinforced. In dogs, rCaIFN-γ may be effective for bolstering antitumor immune capacity.

Influence of general anesthesia with isoflurane following propofol-induction on natural killer cell cytotoxic activities of peripheral blood lymphocytes in dogs.

To investigate influence of general anesthesia on immunological anti-tumor activity, the natural killer (NK) cytotoxic activity of peripheral lymphocytes (PBLs) was measured in 7 dogs anesthetized for 3 hr with isoflurane following propofol-induction (anesthesia group) and 6 dogs without anesthesia (control group). Blood samples were collected before (baseline) and 24, 120 and 192 hr after the anesthesia. The PBLs were isolated via centrifugation with Ficoll-Hypaque solution (density, 1.073), and adherent cells were removed. The NK cytotoxic activity of the isolated PBLs against canine thyroid cancer cells was detected by the colorimetric rose Bengal assay. Significant decrease in the NK cytotoxic activity was observed at 24 hr after the anesthesia, compared with the baseline values and the control group. The NK cytotoxic activities were recovered to the baseline values until 120 hr after the anesthesia. The general anesthesia with isoflurane following propofol-induction decreased the NK cytotoxic activities of PBLs in dogs. This finding has a clinical relevance to the risk of tumor recurrence or metastasis induced by the suppression of immunological anti-tumor activity after general anesthesia in dogs. The results further emphasized the importance of the need to evaluate immune suppression following general anesthesia in animals.