T-helper (Th)1/Th2 imbalance in the peripheral blood of dogs with malignant tumor.

T helper type 1 cell (Th1)/Th2 imbalance has been observed in a variety of pathological condi- tions, including malignant diseases. We evaluated the Th1/Th2 in peripheral blood Th cells by means of intracytoplasmic cytokine analysis in 11 dogs with advanced malignant tumor; four of them showed metastatic tumor. The percentage of Th1 was significantly lower and the percentage of Th2 was signifi- cantly higher in diseased dogs compared to healthy dogs. The percentage of Th1 in three patients with metastatic tumor was significantly lower than that in the patients with non-metastatic tumor. We conclude that the Th1/Th2 balance was polarized to Th2 in dogs with cancer.