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natural killer cells and herpees infections

heapsreal

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Its quite common that cfsers have poor natural killer cell function. After a quick google i found some interesting info on people with poor NK cell function are susceptible to herpees infections. I found it interesting and thought id share it,

NK cells are cytotoxic; small granules in their cytoplasm contain proteins such as perforin and proteases known as granzymes. Upon release in close proximity to a cell slated for killing, perforin forms pores in the cell membrane of the target cell, creating an aqueous channel through which the granzymes and associated molecules can enter, inducing either apoptosis or osmotic cell lysis. 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.

NK cells are activated in response to interferons or macrophage-derived cytokines. They serve to contain viral infections while the adaptive immune response is generating antigen-specific cytotoxic T cells that can clear the infection. Patients deficient in NK cells prove to be highly susceptible to early phases of herpes virus infection.
In order for NK cells to defend the body against viruses and other pathogens, they require mechanisms that enable the determination of whether a cell is infected or not. The exact mechanisms remain the subject of current investigation, but recognition of an "altered self" state is thought to be involved. To control their cytotoxic activity, NK cells possess two types of surface receptors: activating receptors and inhibitory receptors. Most of these receptors are not unique to NK cells and can be present in some T cell subsets as well.

These inhibitory receptors recognize MHC class I alleles, which could explain why NK cells kill cells possessing low levels of MHC class I molecules. This inhibition is crucial to the role played by NK cells. MHC class I molecules consist of the main mechanism by which cells display viral or tumor antigens to cytotoxic T-cells. A common evolutionary adaption to this seen in both intracellular microbes and tumours is a chronic down-regulation of these MHC I molecules, rendering the cell impervious to T-cell mediated immunity. It is believed that NK cells, in turn, evolved as an evolutionary response to this adaption, as the loss of the MHC would deprive these cells of the inhibitory effect of MHC and render these cells vulnerable to NK cell mediated apoptosis.
 

pattismith

Senior Member
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3,931
another study which goes in the same direction:


Natural Killer Cell Deficiencies in a Consecutive Series of Children with Herpetic Encephalitis
2011
Natural killer (NK) cells play a fundamental role in innate and early phases of adaptive immunity against viral infections, both in humans and in animal models.
To date, NK cell deficiencies in patients with severe herpetic infections have been reported in single cases, and their role as predisposing factor is still controversial.

Five children affected by herpetic encephalitis were consecutively admitted to the Anna Meyer Children's Hospital in Florence (Italy) between 2003 and 2005.
We therefore investigated the presence of NK cell deficiencies in a consecutive series of children with herpetic encephalitis.
Five healthy children were included in the study as controls. Differential WBC counts, main Ig and IgE class serum analysis, cytofluorimetric analysis of circulating T, B and NK cells were performed on our study population.
Sequencing of a selected region of CD16A gene transcript was carried out in two patients.
All patients resulted to be affected by deficiencies related to NK cells in respect to controls. One patient was also affected by lymphopenia, while no other significant deficits of immunity were detected in the study population. To date, this is the first survey that demonstrates isolated NK cell deficiencies in a cohort of consecutive patients affected by severe herpes simplex infections. These findings suggest a role for NK cell deficiencies as a predisposing factor for increased susceptibility and severe course of disease in these patients.