The role of regulatory T lymphocytes in immune control of MC-2 fibrosarcoma

The role of T regulatory lymphocytes (T(reg)) particularly in cancer is well known. The goal of the present study was to determine the contribution of these lymphocytes in the regulation of anti-tumor immunity of CBA/HZgr mice against MC-2 fibrosarcoma (4(th) generation of methylcholanthrene induced tumor). The levels of T lymphocytes (CD4+, CD8+ and CD4+CD25+) were determined 8 and 20 days after tumor transplantation. Further, the role of CD4+CD25+ (T(regs)) in tumor-host interaction was evaluated in vitro and in vivo by using specific monoclonal antibodies. We found that splenocytes of both control and T(reg) depleted tumor bearing mice strongly but differently inhibited growth of tumor cells in vitro. While splenocytes of untreated mice exhibited significant decrease of this activity (from 74.4% to 62.6% and 32.95%), the splenocytes of T(reg) depleted mice showed increase of this activity (from 79.5% to 84.3% and 86.2%) from day 6 to day 13 and day 21 after tumor grafting, respectively. Further, upon i.v. injecting specific monoclonal anti-T(reg) antibody tumor immediately prior to tumor cell intracutaneous transplantation, the tumor was rejected after initial growth. In treated mice, the incidence of T(reg) cells was very low initially, reaching normal values two weeks later. These animals were shown to be resistant to tumor transplantation four months later.