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helper T cell

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helper T cell

also

helper cell

n.
Any of the T cells that carry the CD4 glycoprotein receptor on their surface and that when stimulated by foreign antigens release lymphokines that promote the activation and function of B cells and killer T cells. Also called CD4 cell, T4 cell, T-helper cell.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

helper T cell

Helper T lymphocyte, CD4+ T cell Immunology A subset of T lymphocytes with the antigen determinant CD4, which are presented with a foreign antigen in the context of both a self MHC class II antigen and IL-1; once immune recognition or response occurs, HTCs produce various cytokines–eg, IFN-γ, IL-2 and osteoclast-activating factor, which are critical in hematopoietic differentiation, collagen synthesis, and antibody formation; HTCs play a central role in normal and pathologic immune responses by secreting various cytokines–eg, IL-2, IFN-γ, and TNF are involved in cell-mediated immunity Types Type 1–produces IL-2 and IFN-γ; ↑ in infectious granulomatous processes; type 2–produces IL-4 and IL-5; ↑ in atopic disorders, lepromatous leprosy, visceral leishmaniasis and as a clonal expansion in hypereosinophilic syndrome. See CD4, Flow cytometry, Suppressor cells, T cells.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

helper T cell

A subclass of T lymphocytes which provides essential assistance to MACROPHAGES of the immune system. When organisms have been ingested by a MACROPHAGE, antigen is expressed on the macrophage surface at the site of the MAJOR HISTOCOMPATIBILITY COMPLEX (MHC) surface markers. Helper T cells bind to the combination of antigen and MHC and produce the CYTOKINE gamma-interferon. This diffuses to the MACROPHAGE and switches on the killing function so that the organism is destroyed. In the absence of helper T cell assistance the protective function of the immune system is seriously undermined. The HIV attacks and kills helper T cells thus causing acquired immune deficiency (AIDS).
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
References in periodicals archive
Follicular helper T cells are required for systemic autoimmunity.
Liu et al., "Expansion of circulating counterparts of follicular helper T cells in patients with my asthenia gravis," Journal of Neuroimmunology, vol.
In the study, the researchers found that a certain transcription factor, which are molecules in the cell nucleus that control the activity of cells, continually suppresses the killer T cell lineage in helper T cells. Using mice, the team showed that turning off this transcription factor (ThPOK) enabled the helper cells in the body's peripheral areas, like the blood, spleen and the intestine, to override their original programming and to become killer T cells.
If HIV blocks the production of new helper T cells, then "to treat the disease, not only do we need potent antiretroviral drugs to stop the virus from spreading and destroying T cells, we may also need additional therapies to ensure that T cell production starts anew," says McCune.
Further experiments by Lechler's group suggested that leptin modifies the type of response the helper T cells make.
Poorer marital quality was related to higher viral antibody levels, and lower ratios of helper T cells to suppressor cells--another measure of immune suppression.
Using the antibodies, researchers slowed the functions of helper T cells that normally aid in production of antibodies but may "overhelp' in the case of SLE.
Other metaphors popular among immunologists imbue immune system components with the ability to think, recognize and act - tolerance, surveillance, foreigness, helper T cells, rejection.
The hormone target is thymosin alpha1, which promotes the activity of helper T cells, the prime victims of the AIDS virus.
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