Analysis of liver lymphoid cell subsets pre- and post-in vivo administration of human recombinant interleukin 2 in a C57BL/6 murine system.

The systemic administration of high dose recombinant interleukin 2 (RIL-2) can mediate significant reductions in the number of hepatic metastases in a murine system. This effect is sensitive to host irradiation. Both large granular (LGLs) and small (SLs) lymphocytes have been implicated as the cells mediating the antitumor effect. Utilizing selective Percoll fractionation of liver nonparenchymal lymphoid cells, we have attempted to determine the cell types involved in tumor immunotherapy of murine liver metastases during RIL-2 administration. At a RIL-2 dose of 25,000 units given i.p. three times a day, the total number of lymphoid cells seen in murine livers reached a peak on day 6 after the onset of RIL-2 therapy, lasting until day 10 and ranging from 25 to 29 times baseline values. Both LGLs and SLs were identified and SLs made up over one-half the cells present in murine livers. Phenotypic analysis of LGLs and SLs revealed that during exposure to RIL-2, bands 5 + 6 SLs expressed the Thy-1.2, Lyt-2, and Lyt-1 antigens to a greater degree than LGLs. LGLs exposed to RIL-2 demonstrated a decrease in the expression of the asialo GM1 antigen during exposure to RIL-2; however, the 49H.8 antigen normally expressed on natural killer cells and not on circulating T-cells was found only on LGLs. The role of murine liver LGLs and SLs needs to be further characterized.