Spontaneous human lymphocyte-mediated cytotoxicity against tumor target cells. IX. The quantitation of natural killer cell activity

Abstract

On analysis of in vitro assays of human natural killer (NK) cell function the inadequacy of commonly used methods of expressing lytic activity was apparent. A comparison was made of the data obtained using modifications of two equations-the simple exponential fit and the von Krogh equations. Both of these equations were found to satisfy the following essential criteria for use in these assays. First, the majority of the results obtained in the chromium-release assay could be used in data reduction; second, the resultant "dose-response" curve was reduced to linearity; and third, a single numerical expression was obtained which was directly proportional to the cytotoxic activity. Of the two methods the more conventional exponential fit was found to be the simpler to use. The closeness of fit of the experimentally derived data to the ideal curves did not support the possibility that normal lymphocyte preparations contain suppressor cells capable of inhibiting NK activity. Data have also been presented showing that NK-sensitive targets could be categorized with respect to their susceptibility by comparing the slopes of the target cell survival curves obtained using the exponential fit equation. These observations are relevant to the accurate assessment of NK activity in patient populations and to the determination of the effects of disease and its treatment on this activity.

Enhancing immunity by dietary consumption of a probiotic lactic acid bacterium (Bifidobacterium lactis HN019): optimization and definition of cellular immune responses

“…In the MC cell fraction, the activity of natural killer (NK) cells was assessed via lysis of chromium-labelled K562 tumour cells (an NK-speci®c target), as described elsewhere (Pross et al, 1981). Brie¯y, 10 4 target 51 Crlabelled K562 cells were mixed with effector MCs in 96-well round-bottomed tissue culture plates at an effector : target ratio of 50 : 1.…”

Lamina Propria Mononuclear Cells Express and Respond to Interleukin-2 Differently in Crohn's Disease and Ulcerative Colitis.

“…Cytotoxicity was calculated as the percentage of specific 51Cr release using the following formula: Specific release (%) = (Experimental cpmSpontaneous cpm) / (Maximal cpm -Spontaneous cpm) x 100. The results were expressed in lytic unit (LU) per 107 effector cells required to induce 20%specific 51Cr release from 5 x 103 target cells (14).…”

Lymphokine‐Activated Cytotoxicity in Peripheral Blood Mononuclear Cells of Severely Immunocompromised HIV‐Infected Patients

“…For each subject, unactivated and lymphokine-activated specimens were assayed in parallel. Twenty per cent lytic units (LU 20 ) were calculated from the four E:T ratios utilizing software generously provided by Dr Hugh Pross [12].…”