Questions and Answers
What are NK cells considered?
Cytotoxic innate lymphocytes
Where are NK cells derived from?
The same lymphoid precursor as B and T cells
What are the three classes of lymphocytes?
B cell, T cell, NK cell
What is a lymphocyte typically defined as?
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NK cells are most closely related to __________, and have similar effector functions.
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Like CD8 T cells, NK cells are specialized to identify and eliminate virally infected and ________________ cells.
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NK cells can also eliminate ______________ cells.
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Unlike CD8 T cells, NK cells do not have an antigen-specific receptor and generally do not develop memory.
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Which part of the immune system are NK cells classified as and why?
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What do perforins do, and what do they allow granzymes to do?
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Once in the cell, what function do granzymes have?
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Unlike CD8 T cells, NK cells lack A_ specificity.
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Induces cells to go into apoptosis in around 60 min.
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In order to distinguish healthy cells from malignant or infected cells, NK cells express a variety of __________________ on their cell surface.
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There are ______ receptor families expressed on NK cells classified on their structure. Name them.
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In the cytoplasmic region of the receptor in an NK cell, all receptors are chosen as either activating or inhibitory by the A or B_ in the cytoplasmic region of the receptor.
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Phosphorylation of ________ can initiate signaling and phosphorylation of _____________ can dampen signaling.
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This picture shows ZAP-70 (kinase) joining to an _____________ receptor's ITAM.
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____________ binds to ITIM and signals the cell to dampen (make less strong or intense.). What kind of receptor?
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The ligands for activating receptors are often structurally related to MHC class I called __________________, and are only expressed by _____________ cells.
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What type of receptor is A.CD94:NKG2A?
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Study Notes
Natural Killer Cells Overview
- NK cells are cytotoxic innate lymphocytes that play a crucial role in the immune system.
- Derived from the same lymphoid precursor as B and T cells, NK cells contribute to overall immune function.
Lymphocyte Classification
- Three main classes of lymphocytes: B cells, T cells, and NK cells.
- Lymphocytes are typically characterized by their large round nucleus and circular shape.
Relation to Other Immune Cells
- NK cells exhibit similarities to CD8 T cells in function, especially in targeting infected or cancerous cells.
- Both NK cells and CD8 T cells identify and eliminate virally infected or cancerous cells.
Functional Characteristics
- Unlike CD8 T cells, NK cells lack antigen-specific receptors and do not develop memory.
- NK cells are part of the innate immune system, responding quickly to infections without antigen specificity.
Mechanism of Action
- NK cells, similar to cytotoxic T cells, release perforins and granzymes upon recognizing infected or cancerous cells.
- Perforins form pores in target cell membranes, allowing granzymes to enter and trigger apoptosis through activation of caspases.
Activation and Inhibition
- NK cells can be activated in large quantities during immune responses, inducing apoptosis within approximately 60 minutes.
- To differentiate between healthy and abnormal cells, NK cells express a variety of activating and inhibitory receptors.
Receptor Families
- NK cells have several receptor families, including: KIR (Killer Immunoglobulin-like Receptors), KLR (Killer Lectin-like Receptors), and NCR (Natural Cytotoxicity Receptors).
- Various receptors on NK cells can either activate or inhibit their function.
Specific Receptors
- Specific activating receptors include KIR-2DS, KIR-3DS, and KLR (NKG2C).
- Inhibitory receptors include KIR-2DL, KIR-3DL, and KLR (NKG2A).
Signaling Mechanisms
- All NK cell receptors utilize immunoreceptor tyrosine-based motifs (ITAMs) for activation or immunoreceptor tyrosine-based inhibition motifs (ITIMs) for inhibition in their cytoplasmic regions.
- Activation signaling is initiated through phosphorylated ITAMs, while ITIMs, when phosphorylated, recruit phosphatases to dampen signaling.
Development of NK Cells
- NK cells exhibit variegated expression, allowing them to show different combinations of receptor expressions as they mature, contributing to a diverse NK cell population.
Ligands and Activation
- An inhibitory receptor, CD94:NKG2A, recognizes HLA-E complexes, which are derived from MHC I.
- Activating receptors often bind to ligands such as MIC proteins, expressed on stressed cells, aiding in the activation of NK cells in immune responses.
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Test your knowledge on Natural Killer (NK) cells with these flashcards. Learn about their characteristics, derivation, and classification within lymphocytes. Perfect for students studying immunology or related biological fields.
