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Adhesion characteristics of human interleukin 2-activated natural killer cells
R J Melder1, E Walker, R B Herberman
1Department of Pathology, University of Pittsburgh School of Medicine, Pennsylvania 15213.
Insights
Interleukin-2 (IL2) activates natural killer (NK) cells, increasing their adherence to plastic surfaces. This process involves the upregulation of cellular adhesion molecules (CAMs), particularly CD11c, which is crucial for NK cell adhesion and motility.
Area of Science:
- Immunology
- Cell Biology
Background:
- Natural killer (NK) cells are crucial immune cells involved in innate immunity.
- Interleukin-2 (IL2) is a cytokine known to activate and expand NK cells.
- Cellular adhesion molecules (CAMs) mediate cell-cell and cell-substrate interactions.
Purpose of the Study:
- To investigate the role of cellular adhesion molecules (CAMs) in the adherence of IL2-activated human NK cells to plastic.
- To identify specific CAMs involved in the initial adherence and subsequent motility of NK cells.
Main Methods:
- Culture of human peripheral blood mononuclear cells with recombinant IL2 (rIL2).
- Analysis of NK cell surface antigen expression using monoclonal antibodies and flow cytometry.
- Assessment of NK cell adherence to plastic and inhibition by antibodies.
- Immunofluorescence and immunogold electron microscopy to determine CAM distribution.
Main Results:
- IL2-induced adherence and proliferation of a subpopulation of lymphocytes with NK cell characteristics.
- Upregulation of CD11c and CD11a antigens on IL2-activated NK cells within 24 hours.
- Expression of the entire CD11/CD18 family of CAMs after prolonged IL2 incubation.
- Adherence dependent on IL2, divalent cations, cellular metabolism, and CAM expression; CD11c (LeuM5) antibody showed highest inhibition (50-80%).
- CD11c also mediated detachment of adherent NK cells.
- CAMs (except CD56) showed polar distribution on adherent/motile NK cells; CD11b, CD11c, CD2, CD18 clustered on nonadherent cells.
- CAMs, particularly CD11c, were found in cytoplasmic granules, suggesting rapid mobilization.
Conclusions:
- IL2-activated NK cells upregulate CAMs, with CD11c playing a key role in plastic adherence.
- CAMs are stored in cytoplasmic granules, enabling rapid cell surface expression upon activation.
- These findings elucidate the molecular mechanisms underlying NK cell adhesion and motility.
Abstract:
Culture of human monocyte-depleted peripheral blood mononuclear cells with recombinant IL2 (rIL2) induced adherence to plastic by 24 hr and subsequent proliferation in a subpopulation of lymphocytes with phenotypic and functional characteristics of activated natural killer (NK) cells. Purified human NK cells activated in the presence of IL2 for 24 hr upregulated the expression of the CD11c (p150.95) and CD11a antigen but not other cellular adhesion molecules (CAM). After further incubation with IL2, NK cells displayed upregulation of all of the antigens in the CD11/CD18 family of CAM. The process of adhesion was strictly dependent on culture in the presence of IL2, divalent cations, and active cellular metabolism. Adhesion also was dependent on expression of CAM on the cell surface, since monoclonal antibodies to CAM inhibited adhesion of activated NK cells to varying degrees (from 50 to 80%). An antibody (LeuM5) to the CD11c antigen (p150.95) gave the highest level of inhibition, and anti-CD11a (LFA-1) also was inhibitory, while anti-CD56 (NKH1) or anti-CD11b did not interfere with adhesion to plastic. Anti-CD11c was also the most effective in initiating the detachment of adherent-phase NK cells. Antibodies to CD18 or CD2 antigen also inhibited binding of NK cells to plastic. The blocking effects of anti-CD2 and anti-CD11a were additive in this system. On the surface of plastic-adherent and motile NK cells, all CAM except the CD56 antigen had a polar or bipolar distribution, as determined by staining with anti-CAM antibodies. Surface antigens CD11b, CD11c, CD2, and CD18 on nonadherent NK cells were clustered at the cellular poles by both immunofluorescence and immunogold electron microscopy, whereas CD11a (LFA-1) and CD56 antigens were distributed diffusely. CAM, especially CD11c, were also detected in cytoplasmic granules by immunostaining in IL2-activated NK cells. Thus, CAM may be stored in granules, allowing for their rapid transfer to the cell membrane in response to activation. Our results indicate that CAM are upregulated in IL2-activated NK cells and that some of these molecules (e.g., CD11c) play an important role in the development of plastic adherence by a subpopulation of these cells.