Implantation of a gelatin-sponge as a model for effector recruitment. Tumor growth inhibition by T-lymphocytes recovered from a site of tumor rejection.

Nylon-wool-eluted lymphocytes, isolated from a site of tumor rejection in Balb/c mice expressing concomitant tumor immunity, were examined for their ability to inhibit the growth of the EMT6 tumor. Tumor growth inhibition was monitored after co-inoculation of lymphocytes and tumor cells into naive mice in a Winn-type adoptive-transfer assay. A pre-implanted gelatin sponge was employed to capture the tumor-infiltrating lymphocytes. Mice harboring primary tumors were implanted 8 days later with gelatin sponges. The pre-implanted sponges were then inoculated with a secondary tumor challenge 2 days after implantation of the sponge (i.e. 10 days after primary tumor challenge). On day 17 (7 days after secondary tumor challenge), the immune sponges were retrieved, digested in collagenase and the T lymphocytes were isolated using a nylon-wool column. Blank sponges (lacking tumor cells), obtained from primary-tumor-bearing or non-tumor-bearing animals, were included for comparison. The data showed that T lymphocytes isolated from immune sponges inhibited tumor growth while T lymphocytes recovered from blank sponges did not. At an effector:target (E:T) ratio of 10:1 the lymphocytes from the immune sponges were able to prevent totally the growth of tumors in all cases (100% inhibition). This ability was reduced (60% inhibition) at an E:T ratio of 1:1. Comparison of the antitumor activities of the immune-sponge-derived cells with those from the spleen of the same animal revealed the superiority of the former. Depletion of immune-sponge-derived cells with anti-Thy1.2, anti-Lyt2.2 or anti-L3T4 and complement resulted in a marked decrease in tumor-inhibitory activity. These results indicate that T lymphocytes, expressing Thy1.2, Lyt2.2 or L3T4 antigens, are involved in conferring protection to Balb/c mice against the EMT6 tumor.