The difference in surface phenotypes between cytotoxic lymphocytes induced in vivo by systemic administration of human recombinant interleukin-2 and lymphokine activated killer cells induced in vitro.
The cytotoxicity of spleen lymphocytes of C57BL/6 mice is augmented both by incubation of spleen lymphocytes with human recombinant interleukin-2 (rIL-2) in vitro (LAK cell) and by systemic administration of high doses of rIL-2 into C57BL/6 mice for more than 3 consecutive days. In this study, the precursors and effectors of LAK cells and the cytotoxic cells induced by systemic administration of rIL-2 were characterized by using anti-asialoGM1 and anti-Thy1.2 antibody. The in vitro induced LAK cells were demonstrated to be derived partly from asialoGM1 negative cells and the cytotoxicities of LAK cells induced in vitro with rIL-2 were partially resistant to lysis by anti-asialoGM1 antibody plus complement in comparison with NK cells. Contrary to this, the cytotoxicities of spleen lymphocytes of C57BL/6 mice pretreated with anti-asialoGM1 antibody were not augmented by in vivo injection of rIL-2. In addition, the cytotoxic activities of spleen lymphocytes, augmented by systemic administration of rIL-2, were completely suppressed by anti-asialoGM1 antibody and complement in vitro. These findings indicate that the cytotoxic lymphocytes induced in vivo by systemic administration of rIL-2 are different from in vitro induced LAK cells and have the same surface phenotype as NK cells.