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CD3 negative "small agranular lymphocytes" are natural killer cells.
L Inverardi1, J C Witson, S A Fuad
1Department of Laboratory Medicine, University of Minnesota, Minneapolis 55455.
Journal of Immunology (Baltimore, Md. : 1950)
|June 1, 1991
Summary
Small agranular lymphocytes (SAL) exhibit potent K562 cell killing, comparable to granular lymphocytes (LGL). These findings redefine Natural Killer (NK) cells to encompass both SAL and LGL.
Area of Science:
- Immunology
- Cellular Biology
Background:
- Natural Killer (NK) cells are crucial for innate immunity.
- NK cell cytotoxicity is traditionally associated with granular lymphocytes (LGL).
Purpose of the Study:
- To characterize the cytotoxic activity of CD3-, CD16+, and/or CD56+ small lymphocytes.
- To investigate the mechanism of cytotoxicity in these lymphocytes.
- To redefine the concept of NK cells.
Main Methods:
- Flow cytometry (FACS) for cell surface marker analysis.
- Light and electron microscopy for granule assessment.
- Cytotoxicity assays using K562 target cells.
- Inhibition studies with L-leucine methyl ester and EGTA.
Main Results:
- CD3-, CD16+, and/or CD56+ small lymphocytes, termed small "agranular" lymphocytes (SAL), exhibit significant K562 cell killing.
- SAL cytotoxicity is comparable to CD3- LGL on a per-cell basis.
- SAL lack visible granules but possess cytoplasmic lytic molecules sensitive to L-leucine methyl ester and EGTA.
- Both SAL and LGL demonstrate equal and reproducible antibody-dependent cell-mediated cytotoxicity (ADCC).
Conclusions:
- SAL represent a distinct population of cytotoxic lymphocytes.
- The findings necessitate a broader definition of NK cells to include both LGL and SAL.
- This expands our understanding of cellular immunity and cytotoxic lymphocyte subsets.