A study of the effects of irradiation and interferon-γ on susceptibility to lymphokine activated killer cells and cytotoxic T lymphocytes

Abstract

The susceptibility of a mouse squamous cell carcinoma cell line to lymphokine activated killer (LAK) cells and cytotoxic T lymphocytes (CTL) was examined in terms of major histocompatibility complex (MHC) class I expression after various treatments with γ-rays and interferon-γ(IFN-γ). The original NR-S 1 cells were squamous cell carcinomas of C 3 H/He mice; these were used as target cells. The NR-S 1 cells were previously treated with (1) irradiation with 10 Gys of γ-rays, (2) 100 U/ml of IFN-γ, (3) a combination of γ-rays and IFN-γ, or (4) citric acid at pH 3. The highest expression of MHC class I was obtained in the combination group, followed by the IFN-γ and γ-ray groups. The lowest expression was obtained in the citric acid group. As for evidence of adhesion molecules, ICAM-1 was enhanced slightly in the IFN-γ group, but ICAM-2 was not enhanced in any group.
LAK cells were obtained from the splenic lymphocytes of C3H/He, C57BL/6 or BALB/c mice, and incubated with rIL-2 for 3 days. These LAK cells showed 17-27% cytotoxicity against P815 cells, 69-75% against YAC-1 cells, and about 30% against untreated NR-S 1 cells. The target cells in the combination group were the most resistant to LAK cells, and those in the citric acid group were more sensitive than the untreated cells. There was no significant difference in activities among the three strains of mice. Anti-CD 8 antibody or anti-asialo GM 1 antibody was intra-peritoneally administered to these three strains of mice, and the spleen cells were collected. The cytotoxicity of LAK cells from the mice given anti-CD 8 antibody was similar to that of the untreated mice.
In contrast, treatment with anti-asialo GM 1 antibody decreased the cytotoxic activities in all groups. These findings suggest a negative correlation between MHC class I expression and the susceptibility of NR-S 1 to LAK cells. The killer activity was predominantly due to asialo-GM1⁺ cells.
CTL were prepared from untreated C3H/He mice spleen cells. They were incubated with inactivated NR-S 1 cells for 7 days and cultured again with rIL-2 (5 JRU/ml) for 7 days. Although the cytotoxicity of CTL was lower than the LAK activity, it increased in direct proportion to the expression of MHC class I. These findings suggest that CTL would be most effective for adoptive immunotherapy when combined with radiotherapy or cytokine therapy.