T helper cell

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T helper cells (also known as effector T cells or Th cells) are a sub-group of lymphocytes (a type of white blood cell or leukocyte) that play an important role in establishing and maximizing the capabilities of the immune system. These cells are unusual in that they have no cytotoxic or phagocytic activity; they cannot kill infected host (also known as somatic) cells or pathogens, and without other immune cells they would usually be considered useless against an infection. Th cells are involved in activating and directing other immune cells, and are particularly important in the immune system. They are essential in determining B cell antibody class switching, in the activation and growth of cytotoxic T cells, and in maximizing bactericidal activity of phagocytes such as macrophages. It is this diversity in function and their role in influencing other cells that gives T helper cells their name.

Mature Th cells are believed to always express the surface protein CD4. T cells expressing CD4 are also known as CD4+ T cells. CD4+ T cells are generally treated as having a pre-defined role as helper T cells within the immune system, although there are known rare exceptions. For example, there are sub-groups of regulatory T cells, natural killer T cells, and cytotoxic T cells that are known to express CD4 (although cytotoxic examples have been observed in extremely low numbers in specific disease states, they are usually considered non-existent). All of the latter CD4+ T cell groups are not considered T helper cells, and are beyond the scope of this article.

The importance of helper T cells can be seen from HIV, a virus that infects cells that are CD4+ (including helper T cells). Towards the end of an HIV infection the number of functional CD4+ T cells falls, which leads to the symptomatic stage of infection known as the acquired immune deficiency syndrome (AIDS). There are also some rare disorders that result in the absence or dysfunction of CD4+ T cells. These disorders produce similar symptoms, and many of these are fatal.

For more information about T helper cell, read the full article at Wikipedia.
This text uses material from Wikipedia and is available under the GNU Free Documentation License.

News tagged with cd4 t cells

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A reductionist approach to HIV research

Medicine & Health / HIV & AIDS

Nov 30, 2009 | not rated yet | 0

A major obstacle to HIV research is the virus's exquisite specialisation for its human host - meaning that scientists' traditional tools, like the humble lab mouse, can deliver only limited information. Now, a team of researchers ...

HIV vaccine failure probably caused by virus used, says new research

Medicine & Health / HIV & AIDS

Nov 16, 2009 | not rated yet | 0

The recent failure of an HIV vaccine was probably caused by the immune system reacting to the virus 'shell' used to transmit the therapy around the body, according to research published today in the Proceedings of the Na ...

Circulating Mesothelin Serves as a Marker of Pancreatic Cancer

Medicine & Health / Cancer

Oct 22, 2009 | not rated yet | 0

(PhysOrg.com) -- Researchers have expanded on previous studies, and there may be a new weapon in the arsenal for immune-based strategies in treating pancreatic cancer - mesothelin protein. Findings also showed that circulating ...

AIDS patients face higher risk of HPV-related cancers as immunosuppression grows

Medicine & Health / Cancer

Jul 31, 2009 | not rated yet | 0

Risk of human papillomavirus (HPV)-associated cancers is greater for people living with AIDS and increases with increasing immunosuppression, according to a new study published online July 31 in the Journal of the National Ca ...

Earlier AIDS drug treatment would save 76,000 lives over 5 years

Medicine & Health / HIV & AIDS

Jul 27, 2009 | not rated yet | 0

(PhysOrg.com) -- Early initiation of lifesaving antiretroviral therapies should be the standard of care for all HIV-infected patients, even those in countries with limited medical and financial resources, according to a study ...

Study offers insights into failed HIV-1 vaccine trial

Medicine & Health / HIV & AIDS

Jul 20, 2009 | 5 / 5 (1) | 1

Following the disbandment of the STEP trial to test the efficacy of the Merck HIV-1 vaccine candidate in 2007, the leading explanation for why the vaccine was ineffective - and may have even increased susceptibility to acquiring ...

Scientists gain insight into HIV vaccine failure

Medicine & Health / HIV & AIDS

Jul 20, 2009 | 3.5 / 5 (4) | 0

A team of researchers from The Wistar Institute and the University of Pennsylvania reports new evidence refuting a popular hypothesis about the highly publicized failure in 2007 of the Merck STEP HIV vaccine study that cast ...

Earlier HIV antiviral treatment can be cost effective in areas of limited resources

Medicine & Health / HIV & AIDS

Jul 20, 2009 | not rated yet | 0

Early initiation of lifesaving antiretroviral therapies should be the standard of care for all HIV-infected patients, even those in countries with limited medical and financial resources, according to a study led by researchers ...

Chronic infection now clearly tied to immune-system protein (w/Video)

Medicine & Health / Research

May 14, 2009 | 4.8 / 5 (6) | 0

A new study finds the cross-talk between 'killer T-cells' and 'helper T-cells' can only happen in the presence of interleukin-21, a powerful immune-system protein. UAB researchers say if interleukin-21 is missing, the immune ...