Perforins in human cytolytic cells: the effect of age.

The ageing process is associated with a progressive increase in the number of circulating NK cells, together with a decreased lytic activity per cell. A similar decrease in activity was also found for CD8 lymphocytes. Cytotoxic T- and NK cells express cytoplasm granules containing cytolytic effector molecules (as perforins, studied here) which can recognize and destroy damaged, infected and/or mutated target cells.

Standardization of a micro-cytotoxicity assay for human natural killer cell lytic activity.

Cytotoxicity assays are widely used to evaluate the functional activity of NK and T cells against tumour target cells and the release of radioactive sodium chromate from labelled target cells is still the most commonly used marker of target lysis in culture supernatants. We describe here the standardization of a micro-cytotoxicity test in which the number of cytolytic effector and tumour target cells have been decreased by a factor of 10. The release obtained by 500 tumour target cells was compared with the release obtained by 5000 target cells in the standard cytotoxicity assay for target:effector cell ratios from 1:1 to 1:100.