Abstract
Immunotherapy improves both survival and remission rates after cancer surgery in humans, but its veterinary use has been limited. We determined the safety and feasibility of lymphokine-activated killer (LAK) cell transplantation in two aged cats that had undergone surgery for malignancy. Case 1 involved an 18-year-old male Japanese domestic cat. The cat exhibited appetite loss and poor physical activity after surgical excision of oral squamous cell carcinoma followed by four sessions of radiotherapy, and the owner strongly requested immunotherapy for preventing further deterioration in the animal’s quality of life (QOL). We subsequently administered LAK cells three times during a 2-month period. Case 2 involved a 20-year-old female Japanese domestic cat who had undergone mammectomy after a diagnosis of breast adenocarcinoma. The owner strongly requested immunotherapy for QOL maintenance. We administered LAK cells four times over a period of 5 months.
Autologous peripheral blood mononuclear cells (PBMCs) fractionated using density gradient centrifugation were cultured in media containing a high concentration of interleukin-2 and supplemented with 2.5% foetal calf serum. The derived LAK cells were centrifuged, suspended in 10 ml of saline containing 1% of the subject’s own blood, and infused into the cephalic vein of the cats over 30 mins. The composition ratios of CD3, CD4, CD8 and CD21 were evaluated by flow cytometry. Bacterial culture and endotoxin testing for a sample of LAK cells showed negative results in both cases. The leukocyte and erythrocyte counts and the body temperature were assessed on days 7, 14 and 21 after the transfusion. No abnormal signs were observed in either case, which confirmed the safety of the procedure. QOL scores showed no significant changes after the treatment, and the body temperature remained steady throughout the treatment.
The findings from these cases suggest that transplantation of LAK cells derived from PBMCs may be safe and feasible for use in cats, regardless of their age.

Key words: CD4-CD8 ratio, Immunotherapy, Lymphokine-activated killer cells, Transplantation, T lymphocytes.