THE MECHANISM OF T-CELL MEDIATED CYTO-TOXICITY .8. ZEIOSIS CORRESPONDS TO IRREVERSIBLE PHASE (PROGRAMMING FOR LYSIS) IN STEPS LEADING TO LYSIS

  • 1 January 1981
    • journal article
    • research article
    • Vol. 42  (2) , 201-206
Abstract
The combined use of an improved technique for inactivating [murine] cytotoxic T cells during the lytic reaction, with time lapse cinematography and isotope release assay, showed that the initiation of the morphological zeiosis phase corresponds to the time when the target cell is irreversibly programmed to lyse. Apparently Rb release occurs during the zeiosis phase. The rate of Cr release is the result of 2 variable length phases. The reversible phase (before programming for lysis) and the irreversible phase from zeiosis initiation to the final lytic event. The time required for programming for lysis to occur depends on the T cell number reacting with the target cell. Thus at high ratios in tubes, where multiple interactions are possible, most target cells are programmed to lyse within 10 min. Under conditions when T-cell:target-cell conjugates are kept in suspension to prevent multiple interactions, programming for lysis can take several hours. This provides an explanation for the apparent difference in zeiosis timing and programming for lysis in previous publications. Further T-cell interactions with the target cell after programming for lysis (i.e., during the irreversible phase), markedly influence the Cr release rate. This provides an explanation for the fact that Cr release takes at least 3 h to reach plateau levels after T cell inactivation whereas at high effector cell ratios, maximum Cr release level can occur within 1 h.