KINETICS AND FUNCTION OF PERITONEAL-EXUDATE CELLS DURING LOCAL IL-2 GENE-THERAPY OF CANCER

The present study was designed to examine the kinetics and function of peritoneal exudate cells (PEC) during local interleukin 2 (IL-2) gene therapy of the X63-Ag8.653 plasmacytoma growing in the peritoneal cav ity. BALB/c mice were inoculated i.p. on day 0 with a tumorigenic dose of the syngeneic plasmacytoma and on day 1 with non-tumorigenic plasm acytoma cells carrying an inserted IL-2 gene and producing constitutiv ely IL-2. At regular time intervals the experimental mice were sacrifi ced and their peritoneal exudate cells were used for phenotypic analys is and Cr-51 microcytotoxicity assay. On the first day after i.p. inoc ulation of the genetically modified plasmacytoma cells the percentage of Thy 1.2+, CD3+, TCR alphabeta+ T lymphocytes and NK+ cells in the p eritoneal fluid dramatically increased. The levels of the positive cel ls continually decreased until day 11, when the values of normal, heal thy mice were obtained. The percentage of Thy 1.2+ and CD3+ cells rema ined at these, or slightly lower values, until the end of the observat ion period. A similar, though more slowly descending kinetics was seen in the CD5+ cell population, whereas the CD8+ cells, compared to the controls, exhibited only a short-term peak between days 3 and 5, and t he values of TCR alphabeta+ and NK+ cells exhibited a second peak betw een days 25 and 48. The percentage of TCR gammadelta+ cells showed a p ermanent, moderately elevated plateau from day 1 till the end of the o bservation period. In control, untreated mice, inoculated i.p. with th e X63-Ag8.653 plasmacytoma, the kinetics of peritoneal exudate cells w as different. A moderate, permanent elevation of all of the T and NK c ell subsets examined occured during the observation period. In additio n, the percentage of TCR alphabeta+, TCR gammadelta+ and NK+ cells fur ther increased continually from day 11 till the end of the observation period. The cytolytic activity of the peritoneal exudate cells was ex amined in vitro concurrently with FACS phenotyping. Free tumour-specif ic killer cells generated in the peritoneal fluid due to the local IL- 2 gene therapy were found only on day 6, and these cells were cytolyti c for both, the parental X63-Ag8.653 and the genetically modified X63- m-IL-2 plasmacytoma cells.