Natural Killer T cell
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Natural killer T (NKT) cells are a heterogeneous group of T cells that share properties of both T cells and natural killer (NK) cells. Many of these cells recognize the non-polymorphic CD1d molecule, an antigen-presenting molecule that binds self- and foreign lipids and glycolipids. They constitute only 0.2% of all peripheral blood T cells.[1]
Nomenclature
The term “NK T cells” was first used in mice to define a subset of T cells that expressed the natural killer (NK) cell-associated marker NK1.1 (CD161). It is now generally accepted that the term “NKT cells” refers to CD1d-restricted T cells, present in mice and humans, coexpressing a heavily biased, semi-invariant T cell receptor (TCR) and NK cell markers.[1] Natural killer T (NKT) cells should not be confused with natural killer (NK) cells.
Molecular Characterization
NKT cells are a subset of T cells that co-express an αβ T cell receptor (TCR), but also express a variety of molecular markers that are typically associated with NK cells, such as NK1.1. They differ from conventional αβ T cells in that their TCRs are far more limited in diversity and in that they recognize lipids and glycolipids presented by CD1d molecules, a member of the CD1 family of antigen presenting molecules, rather than peptide-MHC complexes. NKT cells include both NK1.1+ and NK1.1-, as well as CD4+, CD4-, CD8+ and CD8- cells. Natural Killer T cells share other features with NK cells as well, such as CD16 and CD56 expression and granzyme production.[1][1]
Classification
Classification of natural killer T cells into three groups has been proposed.[1]
| Type 1 NKT | Type 2 NKT | NKT-Like | |
|---|---|---|---|
| Other names | classical NKT invariant NKT (iNKT) Vα14i NKT (mouse) Vα24i NKT (human) | non-classical NKT diverse NKT | NK1.1+ T cells CD3+ CD56+ T cells |
| Restriction | CD1d | CD1d | MHC, other? |
| α-GalCer reactivity | + | - | - |
| TCR repertoire | Vα14-Jα18: Vβ8.2, 7, 2 (mouse) Vα24-Jα18: Vβ11 (human) | diverse | diverse |
iNKT cells
The best known subset of CD1d-dependent NKT cells expresses an invariant T cell receptor α (TCR-α) chain. These are referred to as type I or invariant NKT cells (iNKT) cells.These cells are conserved between humans and mice and are implicated in many immunological processes.
Function
Upon activation, NK T cells are able to produce large quantities of interferon-gamma, IL-4, and granulocyte-macrophage colony-stimulating factor, as well as multiple other cytokines and chemokines (such as IL-2 and TNF-alpha).
Significance
NKT cells seem to be essential for several aspects of immunity because their dysfunction or deficiency has been shown to lead to the development of autoimmune diseases (such as diabetes or atherosclerosis) and cancers. NKT cells have recently been implicated in the disease progression of human asthma.[1]
The clinical potential of NKT cells lies in the rapid release of cytokines (such as IL-2, IFN-gamma, TNF-alpha, and IL-4) that promote or suppress different immune responses.
References
External links
- NKT cell Journal Screening
- Nature glossary on murine NKT cells
- Nature Reviews Web Focus on regulatory lymphocytes
- NKT/CD1 References @ Antigenics.com
Immune system / Immunology | |
|---|---|
| Systems | Adaptive immune system vs. Innate immune system • Humoral immune system vs. Cellular immune system • Complement system (Anaphylatoxins) • Intrinsic immune system |
| Antibodies and antigens | Antibody (Monoclonal antibodies, Polyclonal antibodies, Autoantibody) • Allotype • Isotype • Idiotype • Antigen (Superantigen) |
| Immune cells | White blood cells (T cell, B cell, NK cell, Mast cell, Basophil, Eosinophil) • Phagocyte (Neutrophil, Macrophage, Dendritic cell) • Antigen-presenting cell • Reticuloendothelial system |
| Immunity vs. tolerance | Immunity • Autoimmunity • Allergy • Tolerance (Central) • Immunodeficiency |
| Immunogenetics | Somatic hypermutation • V(D)J recombination • Immunoglobulin class switching • MHC / HLA |
| Substances | Cytokines • Opsonin • Cytolysin |
| Other | Inflammation • Epitope (Hapten) • Cross-reactivity |
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
