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Participation of the CD94 receptor complex in costimulation of human natural killer cells
1Department of Radiology, Beth Israel Deaconess Medical Center, Boston, MA 02115, USA.
Insights
Human NK cell expansion needs cytokines and cell contact. CD94 receptor ligation boosts CD56(bright) NK cell proliferation and IFN-gamma secretion, unlike CD56(dim) cells, suggesting distinct regulation pathways.
Area of Science:
- Immunology
- Cell Biology
Background:
- Optimal human Natural Killer (NK) cell proliferation and expansion depend on mitogenic cytokines and co-stimulatory signals from cell-to-cell contact.
- The CD94 antigen is a component of a heterodimeric receptor complex on NK cells, implicated in NK cell function.
Purpose of the Study:
- To characterize the CD94 receptor complex and investigate its role in co-stimulating human NK cell subsets.
- To determine if CD94 ligation differentially affects the proliferation and cytokine production of CD56(bright) and CD56(dim) NK cells.
Main Methods:
- Production and characterization of the NKH3 monoclonal antibody (mAb) targeting the CD94 antigen.
- Immunoprecipitation and analysis of the CD94 receptor complex using SDS-PAGE and isoelectric focusing.
- Flow cytometry analysis using NKH3 and Z199 mAbs to assess CD94 and NKG2-A expression on NK cell subsets.
- Functional assays measuring NK cell proliferation and interferon-gamma (IFN-gamma) secretion upon stimulation with cytokines (IL-2, IL-15) and receptor ligation (CD94 mAb, K562 cells).
Main Results:
- The NKH3 mAb identified a heterodimeric complex (~70 kDa) containing CD94, with varying associated molecules.
- CD94 is expressed on most resting NK cells, with higher levels on CD56(bright)CD16(dim/neg) cells compared to CD56(dim)CD16(bright) cells.
- Ligation of CD94 significantly enhanced IL-2/IL-15-induced proliferation and IFN-gamma secretion in CD56(bright) NK cells, but not consistently in CD56(dim) NK cells.
- Irradiated K562 cells co-stimulated both NK cell subsets, indicating alternative co-stimulatory pathways.
Conclusions:
- CD94 acts as a co-stimulatory receptor, primarily for the CD56(bright) NK cell subset, augmenting responses to IL-2 and IL-15.
- Distinct co-stimulatory receptors likely regulate CD56(bright) and CD56(dim) NK cell subsets independently.
- These findings provide insights into the differential regulation of human NK cell subsets in vivo.
Abstract:
Optimal proliferation and expansion of human NK cells require mitogenic cytokines together with cell contact-dependent co-stimulation. Production of mAb that can modulate human NK cell proliferation yielded NKH3, which recognizes the CD94 Ag. NKH3 immunoprecipitates contain approximately 70-kDa heterodimeric complexes consisting of a approximately 25-kDa glycoprotein and approximately 40- to 45-kDa molecules. Analysis by two-dimensional isoelectric focusing/SDS-PAGE suggests that several different 40- to 45-kDa species are present in the CD94 receptor complex in human NK cells. NKH3 reacted with essentially all resting NK cells, although CD94 is expressed at higher levels on the CD56(bright) (i.e., high level of CD56) CD16(dim/neg) (i.e., low level of or absent CD16) subpopulation than on the more abundant CD56(dim)CD16(bright) NK cell subset. Moreover, the Z199 mAb, which appears to recognize NKG2-A species that can form heterodimers with CD94, stained virtually all CD56(bright) NK cells, but only a subset of CD56(dim) NK cells. Ligation of CD94 augmented the proliferation of CD56(bright) NK cells in response to IL-2 or IL-15 by as much as 10-fold. Secretion of IFN-gamma by CD56(bright) NK cells stimulated with IL-2 or IL-15 was also enhanced up to 10-fold after CD94 ligation. CD94 mAb did not consistently costimulate proliferation of or IFN-gamma production by CD56(dim) NK cells cultured with IL-2 or IL-15. In contrast, irradiated K562 cells costimulated proliferation of both CD56(bright) and CD56(dim) NK cells. These results indicate that CD56(bright) and CD56(dim) NK cells can be costimulated through different receptors, which may allow these distinct NK cell subsets to be independently regulated in vivo.
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