CELLULAR

IMMUNDLOGY

Heterogeneity

40, 58-68

(1978)

of Human

Natural

Killer

Cell

Populations1

Natural killing (NK) in human donors was determined hy the ability of peripheral blood subpopulations to lyse the mycloid target. K561, in a 2 to 4 hr “‘Cr release assay. The most active cell was a non-T cell I\-hich passed through nylon columns (representing 10 to 2570 of column passed cells). X second column passed cell population, with characteristics of T lymphocytes (75 to 90% of column passed cells), was also capable of mediating natural killing. Non-T cells which were retained by the nylon columns (45 to 5570 of adherent cells) lacked NK activity. However, nylon adherent T cells (45 to 55% of adherent cells) were consistently active in NK assays, illustrating an important subset of NK effector cell often overlooked. Both column passed and adherent T cells were further separated according to their ability to hind IgG or IgM immune complexes. showing that those mediating NK have receptors for IgG (T+y+) but not for Ighl (T,w+).

IXatural killing (NK)’ is non- a well recognized l~henomenon described in hmm~ (l-Z>, mouse (3-4), and rat systems (5-6). It can be defined as the reactivity of lymphoid cells against certain syngeneic (I), allogeneic (2-6) or xenogeneic (7) tumor cells in the absence of any apparent nntigenic stimulation. The possible significance of natural killing as a mechanism for ilnn~u~7osL~rveillance has generated much interest in the phenomenon and while the in z&o significance of NK in humans is not coml~letely understood there are several animal nmlel systems where tumor resistance (8-9) and bone marrow resistance (10) have been correlated to levels of NK. Considerable controversy has acconq~anietl the recent upsurge of interest in NK. One unresolved question is whether NK and antibody-dependent-cellular cytotoxicity (AAllCC) activities are mediated by the same or different cells. A related problem concerns the nature of the human effector cell(s). It is generally agreed that surface Ig positive I3 cells and macrophages are not effecters in SK. Several authors have identified as the most active SK cell a nomT cell (11, 12) with some acknowledging that a T cell may also contribute to natural killing (13). However, 1 Supported by USPHS Grant No. CA 14236 and USPHS-TG Grant No. CA 09058. 2 Abbreviations used in this paper : NK, natural killing ; ADCC, antibody-dependent-cellular cytotoxicity ; PBL, peripheral blood leukocytes ; PBS, phosphate buffered saline ; MEM, minimal essential medium ; Cp, nylon column passed ; SRC, sheep red blood ccl1 ; RBC, red blood cell ; EA, erythrocyte antibody complex ; and m$, macrophage.

0008-X749/78/0401-0058$02.00/0 Copyright All rights

0 1978 by Academic Press, Inc. of reproduction in any form reserved

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