QUANTITATIVE STUDIES OF NATURAL IMMUNITY TO SOLID TUMORS IN RATS - THE NATURE OF THE KILLER CELL DEPENDS ON THE TYPE OF ASSAY

  • 1 January 1980
    • journal article
    • research article
    • Vol. 41  (3) , 673-680
Abstract
Cell fractionation techniques were used to identify the cells in rat spleen responsible for natural killing of a syngeneic sarcoma cell [rat 3-methylcholanthrene-induced sarcoma Mc7 cells] in short-term (6 h and 8 h) and long-term (72 h) cytotoxicity assays. Cytotoxicity was quantified precisely using a method previously derived from consideration of natural cytotoxicity as an enzyme-substrate reaction, and by analyzing results in terms of lytic units. Killing in all 3 assays displayed single-hit kinetics implying that a single effector cell was sufficient to lyse a single target cell. The fractionation studies, using glass adherence, carbonyl iron, nylon wood, EAC [sheep erythrocyte, antibody, complement] EA and monolayers and congenitally athymic rats, revealed 2 populations of cytotoxic cells. In the 6 h assay most of the activity was due to cells with similar characteristics to the NK [natural killer] cells previously defined using leukemic targets; in the 18 h and 72 h assays macrophages played an important role. The activity exerted by the macrophages was cell lysis and not cytostasis. No evidence that the macrophages acted by releasing factors which stimulated NK cells was found.