Babylon 10
The world's best online dictionary

Download it's free

Definition of T4 cell

T4 cell Definition from Medicine Dictionaries & Glossaries
Dictionary of Medicine (Shahram)
Immune cells that are triggered by antibodies to seek and attack invading organisms. Cells called macrophanges summon T4 cells to the site of the infection and present a protruding antigen onto which the T4 cell locks, thus "recognizing" the invading substance. The T4 cell then reproduces and secretes its potent lymphokine hormones that stimulate B-cell production of antibodies; signal "natural killer" or cytotoxic (cell-killing) T-cells; and summon more macrophanges to the site of the infection. T4 cells are normally twice as common as T8 cells. If a person has AIDS, the proportion of T4 to T8 cells is often reversed. T4 cell are also called T-helper cells.
Aids Glossary
a protein embedded in the surface of some T-cells and certain other cells (e.g., macrophages, Langerhans cells, glial cells). HIV invades cells by attaching to their CD4 receptor.
A subset of T cells. Physicians regularly measure T-helper cell counts in HIV positive people. The normal range for T-helper cells is 480-1800, but may vary.
Glossary of HIV/AIDS-Related Terms
(Also called T-helper cell). Antibody-triggered immune cells that seek and attack invading organisms. Macrophages<!-- (see) --> summon T4 cells to the infection site. There the T4 cell reproduces and secretes its potent lymphokines<!-- (see) --> that stimulate B cell<!-- (see) --> production of antibodies; signal natural killer or cytotoxic (cell-killing) T cells<!-- (see) --> and summon other macrophages to the infection site. In healthy immune systems, T4 cells are twice as common as T8 cells. If a person has AIDS, the proportion is often reversed. The virus enters T4 cells through its receptor protein and encodes its genetic information into the host cell's DNA, making T cells virtual viral factories. HIV-infected T4 cells may not die, but, rather, may cease to function. They also begin to secrete a substance known as Soluble Suppressor Factor that inhibits the functioning of even unaffected T cells.
1. A type of T cell involved in protecting against viral, fungal, and protozoal infections. These cells normally orchestrate the immune response, signaling other cells in the immune system to perform their special functions. Also known as T helper cells. 2. HIV's preferred targets are cells that have a docking molecule called "cluster designation 4" (CD4) on their surfaces. Cells with this molecule are known as CD4-positive (or CD4+) cells. Destruction of CD4+ lymphocytes is the major cause of the immunodeficiency observed in AIDS, and decreasing CD4+ lymphocyte levels appear to be the best indicator for developing opportunistic infections. Although CD4 counts fall, the total T cell level remains fairly constant through the course of HIV disease, due to a concomitant increase in the CD8+ cells. The ratio of CD4+ to CD8+ cells is therefore an important measure of disease progression. See CD8 (T8) Cells; Immunodeficiency.
Glossary of HIV/AIDS Terms
A type of white blood cell that activates T-killer cells and helps stimulate antibody production. Physicians regularly measure T-helper cell counts (CD4 counts) in HIV-positive people to monitor immune system function. The normal range for T-helper cells is 480-1800, but may vary in individuals. HIV first enters cells by attaching itself to the CD4 receptor on the surface of T-helper cells.
T4 cell Definition from Encyclopedia Dictionaries & Glossaries
Wikipedia English - The Free Encyclopedia
T helper cells (Th cells) are a sub-group of lymphocytes, a type of white blood cell, that play an important role in the immune system, particularly in the adaptive immune system. They help the activity of other immune cells by releasing T cell cytokines. They are essential in B cell antibody class switching, in the activation and growth of cytotoxic T cells, and in maximizing bactericidal activity of phagocytes such as macrophages.

See more at
© This article uses material from Wikipedia® and is licensed under the GNU Free Documentation License and under the Creative Commons Attribution-ShareAlike License