SANA ISAA SOULIMAN
SANA ISAA SOULIMAN
SANA ISAA SOULIMAN
SANA ISAA SOULIMAN
Natural killer cells:- or NK are a type of cytotoxic lymphocyte critical to the 
innate immune system.
...
SANA ISAA SOULIMAN
SANA ISAA SOULIMAN
NK cell receptors
can also be differentiated based on function. Natural cytotoxicity
receptors directly...
SANA ISAA SOULIMAN
Activating receptors
Inhibitory receptors
SANA ISAA SOULIMAN
SANA ISAA SOULIMAN
NK cell receptor types
*Ly49 (homodimers), relatively ancient, C-type lectin family receptors, are of
m...
SANA ISAA SOULIMAN
Inhibitory receptors
*Killer-cell immunoglobulin-like receptors (KIRs) belong to a multigene family of
...
SANA ISAA SOULIMAN
NK cells form an early line of defence against viruses and
they do this by killing virally-infected cel...
SANA ISAA SOULIMAN
SANA ISAA SOULIMAN
SANA ISAA SOULIMAN
SANA ISAA SOULIMAN
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Natural killer cells

خلايا الطبيعيه القاتله
Published on: Mar 3, 2016
Published in: Education      
Source: www.slideshare.net


Transcripts - Natural killer cells

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  • 4. SANA ISAA SOULIMAN Natural killer cells:- or NK are a type of cytotoxic lymphocyte critical to the  innate immune system.  The role NK cells play is analogous to that of cytotoxic T cells in the vertebrate  adaptive immune response. NK cells provide rapid responses to viral-infected cells  and respond to tumor formation, acting at around 3 days after infection. Typically, immune cells detect major histocompatibility complex (MHC) presented on infected  cell surfaces, triggering cytokine release, causing lysis or apoptosis. NK cells are  unique, however, as they have the ability to recognize stressed cells in the absence  of antibodies and MHC, allowing for a much faster immune reaction.  They were named “natural killers” because of the initial notion that they do not  require activation to kill cells that are missing “self” markers of MHC class 1.  This role is especially important because harmful cells that are missing MHC 1  markers cannot be detected and destroyed by other immune cells, such as T  lymphocyte cells.
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  • 6. SANA ISAA SOULIMAN NK cell receptors can also be differentiated based on function. Natural cytotoxicity receptors directly induce apoptosis after binding to ligands that directly indicate infection of a cell. The MHC-dependent receptors use an alternate pathway to induce apoptosis in infected cells. Natural killer cell activation is determined by the balance of inhibitory and activating receptor stimulation. For example, if the inhibitory receptor signaling is more prominent, then NK cell activity will be inhibited; similarly, if the activating signal is dominant, then NK cell activation will result.
  • 7. SANA ISAA SOULIMAN Activating receptors Inhibitory receptors
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  • 9. SANA ISAA SOULIMAN NK cell receptor types *Ly49 (homodimers), relatively ancient, C-type lectin family receptors, are of multigenic presence in mice, while humans have only one pseudogenic Ly49, the receptor for classical (polymorphic) MHC I molecules. *NCR )natural cytotoxicity receptors), upon stimulation, mediate NK killing and release of IFNγ. *CD94 (Cluster of Differentiation) : NKG2 (heterodimers), a C-type lectin family receptor, is conserved in both rodents and primates and identifies nonclassical (also nonpolymorphic) MHC I molecules such as HLA-E. Expression of HLA-E at the cell surface is dependent on the presence of nonamer peptide epitope derived from the signal sequence of classical MHC class I molecules, which is generated by the sequential action of signal peptide peptidase and the proteasome. Though indirect, this is a way to survey the levels of classical (polymorphic) HLA molecules. *CD16 (FcγIIIA) plays a role in antibody-dependent cell-mediated cytotoxicity; in particular, they bind IgG. Activating receptors
  • 10. SANA ISAA SOULIMAN Inhibitory receptors *Killer-cell immunoglobulin-like receptors (KIRs) belong to a multigene family of more recentlyevolved Ig-like extracellular domain receptors; they are present in nonhuman primates, and are the main receptors for both classical MHC I (HLA- A, HLA-B, HLA-C) and nonclassical HLA-G in primates. Some KIRs are specific for certain HLA subtypes. Most KIRs are inhibitory and dominant. Regular cells express MHC class 1, so are recognised by KIR receptors and NK cell killing is inhibited. *ILT or LIR (leukocyte inhibitory receptors) — are recently discovered members of the Ig receptor family. *Ly49 (homodimers) have both activating and inhibitory isoforms. They are highly polymorphic on the population level; though they are structurally unrelated to KIRs, they are the functional homologues of KIRs in mice, including the expression pattern. Ly49s are receptor for classical (polymorphic) MHC I molecules
  • 11. SANA ISAA SOULIMAN NK cells form an early line of defence against viruses and they do this by killing virally-infected cells. This is achieved by the release of two agents contained within granules in the NK cell. The first agent is called Perforin which forms pores in the virally-infected host cell. The second agent are called Granzymes which cause the apoptosis (programmed cell death) of the virally-infected host cell. NK cells recognise the virally-infected cells due to the lack of MHC Class I on the surface of the cells. Viruses are capable of redirecting MHC Class I away from the surface of host cells so that it is not expressed. When MHC Class I is present on the surface of host cells it interacts with an inhibitory receptor on the NK cell to prevent the NK cell from releasing Perforin and Granzymes. When the MHC Class I is absent it cannot interact with the NK cells inhibitory receptor and so the NK cell is stimulated to release the Perforin and Granzymes
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