# data[].attributes.body
CD8+ and CD

# data[].attributes.body
CD8+ machanism

# data[].attributes.body
Summarize of the NK cells.

http://www.ciml.univ-mrs.fr/science/lab-eric-vivier/home

# data[].attributes.body
Under normal physiological conditions, NK cell activity is inhibited through the interaction of their inhibitory receptors with major histocompatibility complex (MHC) class I. However, upon instances of cellular stress that are frequently associated with viral infection and malignant transformation, ligands for activating receptors are often upregulated and MHC class I expression may be downregulated. The upregulation of these activating ligands and downregulation of MHC class I thus provides a signal for NK cells to become activated and display effector functions. Activating receptors are able to provide NK cells with a strong stimulus in the absence of co-stimulation due to the presence of adaptor molecules such as DAP10, DAP12, FcRγ, and CD3ζ that contain immunoreceptor tyrosine-based activating motifs (ITAMs). By contrast, inhibitory receptors contain inhibitory motifs (ITIMs) within their cytoplasmic tails that can activate downstream targets such as SHP-1 and SHP-2 and directly antagonize those signaling pathways activated through ITAMs.

http://www.nature.com/cdd/journal/v21/n1/full/cdd201326a.html?foxtrotcallback=true

# data[].attributes.body
Upon release in close proximity to a cell slated for killing, perforin forms pores in the cell membrane of the target cell through which the granzymes and associated molecules can enter, inducing apoptosis. The distinction between apoptosis and cell lysis is important in immunology - lysing a virus-infected cell would only release the virions, whereas apoptosis leads to destruction of the virus inside.

Stress induces specific intrinsic and extrinsic physiological mechanisms within cells that lead to their identification as functionally abnormal. Sources of cellular stress can be nutritional, physical, pathogenic, or oncogenic. Intrinsic responses to cellular stress include activation of the DNA-damage response, tumor-suppressor genes, and senescence. The extrinsic response to cellular stress is activation of the immune system, such as natural killer cells. Intrinsic responses to cellular stress can directly upregulate factors that can activate the immune system, and the immune system been shown to be indispensable for the efficacy of some chemotherapy.

https://www.sciencedaily.com/terms/natural_killer_cell.htm

# data[].attributes.body
NK cells were first described as cells that have the ability to kill tumour cells without any priming or prior activation (remember that e.g. cytotoxic T cells need priming by antigen presenting cells) and their name is ultimately connected to this ‘natural’ ability to kill. Additionally, NK cells secrete cytokines, as for example INFg  and TNFa, which constitute a second important defence mechanism during an immune reaction.

# data[].attributes.body
The role of CD8 T cells in adaptive immune responses : respond through their T cell receptors to diverse antigens presented by MHC class I molecules by proliferating, secreting cytokines and chemokines, and directly lysing infected cells. The role for CD8 T cells in the innate immune response: Independent of T cell receptor ligation, CD8 T cells can mount a response against pathogens by secreting cytokines and can defend against tumors by directly killing transformed cells. This innate response has been shown to be beneficial in controlling several types of bacterial infections. However, a subset of CD8 T cells that have innate non-antigen-specific capabilities has been implicated in self-reactivity, which could lead to autoimmunity.

# data[].attributes.body
Natural killer cells or NK cells are a type of cytotoxic lymphocyte critical to the innate immune system. The role NK cells play is analogous to that of cytotoxic T cellsin the vertebrate adaptive immune response. NK cells provide rapid responses to viral-infected cells, acting at around 3 days after infection, and respond to tumorformation. 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 I markers cannot be detected and destroyed by other immune cells, such as T lymphocyte cells.
CD8+ T-cells are a critical component of the cellular immune response and they play an important role in the control of viral infection. During infection, CD8+ T-cells are able to recognize infected cells through an MHC-I dependent process and are able to lyse cells harboring viral infection by the secretion of perforin and granzymes. These cytotoxic T-lymphocytes (CTL) can also eliminate virally infected cells through the engagement of death-inducing ligands expressed by CD8+ T-cells with death receptors on the surface of the infected cell. In addition, CD8+ CTL secrete soluble factors such as beta-chemokines and the CD8+ antiviral factor (CAF) that suppress viral binding and transcription, respectively. In order for virus to survive the pressures placed upon it by the immune system, the virus has adopted numerous strategies to evade the CD8+ T-cell response. The high mutation rate of HIV has allowed the virus to escape CD8+ T-cell recognition in addition to its ability to down-regulate surface MHC-I expression from infected cells. Also, by altering the pattern of cytokine production and engagement of cellular receptors, virus disrupts proper CD8+ T-cell signaling. The resultant improper T-cell receptor (TcR) stimulation creates an anergic state in these cells. By affecting the function of CD4+ T-cells and antigen presenting cells that are required for proper CD8+ T-cell maturation, virus is able to decrease the circulating pool of effector and memory CD8+ T-cells that are able to combat viral infection. The end result is the aberration of CD8+ T-cell function.

# data[].attributes.body
NK CELLS
natural killer (nk) cells are a population of innate cells optimized to kills virus-infected cells. NK cells , a form of lymphocyte, can kill virus-infected or other "abnormal" cells that fail to express major histocompatibility complex (MHC) class 1 molecules. MHC class 1 molecules bind to NK cell receptors and switch off their killing abilities.
in the absence of this signal, the NK cells bind to target cells, inject them with apoptosis-indusing proteins,and kill them
( merck 11th ed page 814 paragraph 3 line 3 )
CD8
cell mediated involves T-lymphocytes that born in bone marrow but mature in thymus.
thymus- check/test the premature of T-cells that it will not attack our own cell body.
Hleper T-cells
help to differentiate other cell of immune system
helper T-cells release chemicals called interleukin and interferons.
these chemical help B-lymphocytes mature into plasma and memory B cells
T- lymphocytes contain membrane , T-cells receptors. These cells can bind to antigen complexes and with the help of helper T cells differentiate into cytotoxic T-cells (killer T cells)
cytotoxic t lymphocyte express as CD8.
Each T cell expresses a unique receptor, within a highly diverse repertoire generated by V(D)J recombination
• Scan MHC class I-peptide complexes, searching for pathogen or tumor encoded antigens
• Preactivation and differentiation required
these cytotoxic T-cells travel to the infected area and bind to specific antigens. once bound, the release powerful proteins that can drill holes and kills the pathogen. In addition,  T-lymphocytes can also form its own memory T-cells as well as a suppressor cells that can regulate and tone down the immune response.
(source : last two years lecture notes)

# data[].attributes.body
NK cells belong to the innate immune system and form a first line of defence against a wide variety of pathological challenges. They provide protection against viral and bacterial infections and they help to detect and limit the development of cancer. This is the  structure of a NK cell. It consists both inhibitory and activating receptor.

# data[].attributes.body
*NK cell belong to the family of group 1 innate lymphocytes (ILC1) and are functionally characterized by their cytotoxicity and their ability to produce cytokines, most prominently interferon γ (IFNγ).
*NK cells are geared to sense sudden cellular changes that can be caused by infection events, malignant transformation, or cellular stress responses.
*NK cell r innate respond n they can react to rapid changes in host cells without prior sensitization
*NK cells are activated via innate cytokines such as IL-2, IL-12, IL-15, IL-18, and type I IFNs as well as viathe recognition of sudden cellular changes perceived via different inhibitory and activating receptors expressed on their surface (1–7).
*direct triggering of toll-like receptors (TLRs) on NK cells can further stimulate their activation (8–10).
*T cells, when activated by TCR engagement (signal 1), costimulation (signal 2), and cytokines (signal 3), commit to a number of cellular alterations, including entry into rapid cell cycling, metabolic changes, and acquisition of effector functions.

# data[].attributes.body
•NK cells are not only controlled the antigens, but also help to activate other agents of the immune system

•NK cells are primarily killer cells.

•Will be helped by other cells of the innate immune system (neutrophils, monocytes, macrophages, dendritic cells)

•Together, they patrol the body and mark cancer or infected cells.

•Once identified, the sick cell are destroyed in minutes by a mechanism known as cytotoxicity: the NK cells attack in packs by releasing substances that perforate the "skin" of their victims; this is death by cell lysis (just like the one Sabby wrote)

•Meanwhile, the NK cells secrete cytokines (the "hormones" of the immune system) that stimulate and guide the response of other agents of innate immunity and lymphocytes of the adaptive immune system

•Eventually, antibodies against that specific agent will be developed, and if there's next encounter with the same antigen,the cells can quickly recognize and remove it! This what we called as memory cells

•then how NK cells differentiate between normal cells and pathogenic cells?!

•throughout evolution, they developed a sophisticated detection system. How it works?!

-All normal cells in the body express MHC I to signal that those cells are part of the body. So normal/healthy cells send inhibitory signals, and those signal will be received by Inhibitory receptors on NK cells. they will recognize MHC class I alleles, which inhibits the NK killing response

-on the other hand, abnormal/pathogenic cell didnt possess MHC class 1 molecule, and they release danger signal and unable to send protective and inyhibitory signal

-those signal will be processed by NK cells, and they will make decision!

-NK cells are cytotoxic; small granules in their cytoplasm contain proteins such as perforin and proteases known as granzymes that trigger either apoptosis or cell lysis in an abnormal cell

https://courses.lumenlearning.com/boundless-ap/chapter/innate-immunity/

# data[].attributes.body
Nk cells are subsets of lymphocytes aside from B cells and T cells. The belong to the innate immune system and is the first line of defence. They provide protection against viral and bacterial infevtion and also against the dev of tumor.NK cells were first described as cells that have the ability to kill tumour cells without any priming or prior activation (remember that e.g. cytotoxic T cells need priming by antigen presenting cells) and their name is ultimately connected to this ‘natural’ ability to kill.
Nk cells secrete cytokines as their defence mechanism.

Nk cells expresses inhibitory receptors thus their are able to detect MHC Class 1, this acts as regulation to avoid the Nk cell from destroying healthy cells as most healthy (normal) cells expresses the MHC Class 1. Thus this avoid unnecessary attack and damage to cells.
https://www.immunology.org/public-information/bitesized-immunology/cells/natural-killer-cells

CD8 t cells is produced in the thymus, they express T cell receptor. Like NK cells they also recognise peptide found on MHC Class 1 receptor on normal cells. They play an important role in immune defence against intracellular pathogens, including viruses and bacteria, and for tumour surveillance.cutotoxic will recognise an antogen and become activated. Immunity will be provided by 3 ways.
1) secretion of cytokines, primarily TNF-α and IFN-γ, which have anti-tumour and anti-viral microbial effects.
2) releasing cytotoxic granules (also found in NK cells). The granules contain granzyme and perforin. Perforin forms pores on the membrane of the targeted cells. This pores allows granzymes to enter into the cells.  Granzymes are serine proteases which cleave the proteins inside the cell, shutting down the production of viral proteins and ultimately resulting in apoptosis of the target cell.
Cytotoxic t cells are able of serial killing, their action will not affect cells within the vicinity of the targeted cells.
3) kill infected cells through Fas/FasL interaction. Activated CD8 cells expressed FasL on its cell surface and will bind with the Fas receptor present on the target cell. This action causes Fas molecules on the target cell to trimerise and pulls signaling molecules.
These moleculedls result in the activation of caspase cascade and result in the apoptosis of the cell.
https://www.immunology.org/public-information/bitesized-immunology/cells/cd8-t-cells

# data[].attributes.headline
NK CELLS and CD8+ T cells (Cytotoxic T Cells) - PUTRI SABREENA (182201) 

# data[].attributes.subject
NK CELLS and CD8+ T cells (Cytotoxic T Cells) - PUTRI SABREENA (182201) 

# data[].attributes.body
NK cells are one of the most aggressive soldiers of the immune system
- They do not have to bind to a specific antigen to release toxins in order to destroy a viral infected cell/cancer cells
- Also, they destroy an infected cell via contact
Mechanism of NK cells:
1) NK cell first binds to the target cell
2) NK cell releases a lethal toxin causing holes to be present on the membrane of the infected cell (destroying both structural and functional integrity)
3) Once the membrane is destroyed, the DNA of the infected cell will be cleaved to small pieces in a programmed cell death known as apoptosis
4) NK cells can immediately detach from the infected cell and target other abnormal cells found in the circulation
5) NK cells also functions in immunoregulation by secreting high levels of lymphokines; this is especially important in immunosuppressed individuals where control of the immune system is needed

- CD8+ T cells are also known as cytotoxic T cells
- Cytotoxic T cells functions to kill both cancerous cells and viral infected cells (sounds familiar doesn't it?)
- In a simplified way, I shall share with everyone how cytotoxic T cells work in the body:
1) Once a cell is infected with virus/it appears to cancerous, the cytotoxic T cells starts binding with them
2) With that being said, it is important to take note that these T cells only bind to MHC Class 1 where it will then differentiate to become either memory cells (in case it comes up again, we dont want no cancer!) or effector T cells (which actually does the killing)
3) How does the cyotoxic T cells cause the cells to kill themselves? They secrete proteins that either causes holes in the membrane/cytoplasm of the cell causing these infected cells to die

By the way! It is also crucial to take note that NK cells work in the innate immunity while the T cells work in the adaptive immunity.

Now, it gets even more complicated xD

Source: Youtube
(https://www.youtube.com/watch?v=oqI4skjr6lQ)
(https://www.youtube.com/watch?v=HNP1EAYLhOs)