9th Page Flashcards
What percentage of the total lymphocyte population do NK cells represent?
10-15% . Other sources indicate 5 to 10%.
Immunity of NK cells
Innate immunity
making them non-specific compared to T and B cells.
What is the approximate size of NK cells?
NK cells are generally larger than T and B cells, approximately 15 um in diameter.
What is a notable feature of NK cell?
NK cells contain kidney-shaped nuclei with condensed chromatin and prominent nucleoli.
What are NK cells also known as?
Large Granular Lymphocytes (LGL).
NK cells stand for?
Natural killer cells
because they can mediate cytolytic reactions and kill target cells without prior exposure.
From where do NK cells arise?
from the common lymphoid progenitor.
NK cells once activated by IL-2, they are called what?
Lymphokine Activated Killer Cells (LAK)
Do NK cells express markers of T or B cells?
They DO NOT
What specific combination of markers can be used for NK cell identification?
CD16, CD56, and CD94.
(NK cells have no unique surface markers)
Role of NK cells in virus immunity?
essential mediators of virus immunity
(their deficiency in humans leads to uncontrolled viral replication and poor clinical outcomes.)
How do NK cells destroy infected or tumor cells?
Destroy without MHC restriction (MHC-unrestricted cytolysis) or antigen presentation.
What do NK cells kill?
Kill virally infected cells or cancerous cells through the secretion of Granzyme and Perforin.
(similar with cytotoxic T cell)
Inhibition signals of NK cells?
Inhibition occurs when NK cells react with MHC class I proteins expressed on healthy cells.
What happens to diseased and cancerous cells regarding MHC proteins?
Lose their ability to produce MHC proteins, leading to killing by NK cells.
Examples of inhibitory receptors found in NK cells
Killer cell immunoglobulin-like receptors (KIRs)
CD94/NKG2A.
ADCC stands for?
Antibody-dependent Cell Cytotoxicity.
ADCC binding occurs through?
CD16 receptor for IgG.
What happens to target cells coated with IgG?
bound and destroyed by NK cells
What is the role of antibodies in NK cell activity?
Antibodies bind antigens on the surface of target cells, allowing NK cells to recognize and destroy them.
What triggers degranulation in NK cells?
Cross-linking of CD16 triggers degranulation into a lytic synapse.
End result for tumor cells attacked by NK cells?
Die by apoptosis.
What NK receptors recognize cell-bound antibodies?
CD16 Fc receptors
What is Flow Cytometry?
A rapid and convenient technique for generating immunophenotypic data.
What is Flow Cytometry useful for?
Evaluation and prognosis of leukemia, lymphoma, and immunodeficiency.
What is the principle behind Flow Cytometry?
Based on Light Scattering derived from suspension of particles in a flowing stream of fluid.
What does Forward Scatter (FSC) measure?
Cell size.
What does Side Scatter (SS) measure?
Cell internal complexity / granularity.
What is the role of the fluorescence detector in Flow Cytometry?
Quantifying cell subpopulations or cell components.
What are common fluorophores used in Flow Cytometry?
FITC, TRITC, Phycoerythin.
**FITC- Fluorescein Isothiocyanate
TRITC - Tetramethylrhodamine Isothiocyanate
What specimens are used in Flow Cytometry?
Blood
Bone Marrow
Body fluid aspirates
Tissue samples.
What anticoagulants are used in Flow Cytometry?
EDTA, Heparin, Acid Citrate Dextrose.
What is required before testing in Flow Cytometry?
Removal of RBCs.
Solution used in density gradient centrifugation in Flow Cytometry
Ficoll-Hypaque solution
What layers are formed during density gradient centrifugation?
Plasma (top)
Mononuclear cells (middle)
RBCs and granulocytes (bottom)
What agent is used for erythrocyte lysing?
Ammonium Chloride.
What is the Rosette technique?
Uses sheep RBCs as reagents for enumeration of T lymphocytes.
Sheep RBCs in Rosette technique
They attach to the CD2 antigen, found only on T cells.
At least how many sheep RBCs attach to a lymphocyte in rosette formation?
3
How is rosette technique calculated?
200 cells are counted and the percent forming rosettes is calculated.
