[Experimental study on the antitumor activity of regional lymph nodes during immunotherapy]

In ascites hepatoma MH134-bearing C3H/He mice, the hemolytic streptococcus preparation OK-432 was administered as model immunotherapy for malignant tumors, and the significance of the presence of regional lymph nodes and changes in cellular immunological competence were investigated. The antitumor effects of OK-432 were greater in tumor-bearing mice in which the regional lymph nodes were preserved than in those lacking regional lymph nodes, showing the significance of the presence of regional lymph nodes during immunotherapy. Regarding lymphocytes in the regional lymph nodes, the Thy 1,2 antigen positive cell ratio, PHA blast formation reaction, cytotoxic activity against YAC-1 cells and MH134 cells as the target cells were determined. Although these values were decreased in proportion to the progress of the tumor, the administration of OK-432 suppressed the decrease. In terms of the increase ratio of the values after the administration of OK-432, the effects of OK-432 on the regional lymph nodes were greater than those on other lymph nodes. It is presumed that immunotherapy suppressed a decrease in cellular immunological competence of regional lymph nodes in proportion to the progress of the tumor and allowed the recovery of the antitumor activity.