What is the function of the cytotoxic T cells?

Answer 1

Cytotoxic T cell's primary responsibility is to kill infected cells. I'll start from the beginning.

From a progenitor cell in the bone marrow, the T cell will begin maturation in the thymus. In the thymus it begins in the cortex as a pro T cell. In this stage it is considered a double negative cell (I'll explain more later). Here it has the beta chain (V,D,J's) rearranged. Next it becomes a pre T cell. By now the T cell has finished rearranging its beta chain and now begins rearrangement of its alpha chain.

Both the beta and alpha chain under go allelic exclusion. This prevents one of the alleles from being expressed (this would be mom's or dad's). If the pro T cell made a beta chain from your mothers allele, your father's allele would be suppressed. This is an important feature, otherwise you could accidentally make a stop codon and that would stop your T cell development right there.

So as a pre T cell it continues to proliferate and it upregulates CD3, CD4 and CD8. You have two types of T cells that it can mature to. CD4 and CD8. A CD4 T cell is also known as a helper T cell and a CD8 T cell is also called a cytotoxic T cell. They function very differently but at this point the T cell doesn't know which one it will become. Therefore it is at this juncture a double positive thymocyte.

The next phase is an immature T cell. Here the alpha chains have finished rearrangement (also allelic exclusion applies here). Now the cell will undergo positive and negative selection. The immature T cell is tested by thymic epithelial cells (TEC). TEC's have a unique feature that belongs to professional antigen presenting cells (APC's) and that is expressing both MHC class I and MHC class II on its cell surface. An immature T cell that can bind to a TEC's MHC class I or MHC class II is positively selected to continue maturation. This is an important step because ensures that your T cells are specific for your body's MHCs. However, if the immature sticks too strongly, it will be neglected and eventually die. You don't want a mature T cell that binds way too strongly on your own cells either. Those that don't bind at all will also die by neglect. The strict standards ends up killing about 95% of all maturing T cells. The immature T cell that was capable of binding to MHC class I molecule is signaled to become a CD8 or cytotoxic cell and the immature T cell that was capable of binding to MHC class II molecule is signaled to become a CD4 or helper T cell.

Now that your immature T cells have been primed to your own body, it will undergo negative selection. In this process it is exposed to other types of cells, dendritic cells and macrophages. Dendritic cells and macrophages are part of your APCs. If the T cell binds too strongly it will also die by neglect.

Congratulations! Your immature T cell is now a mature naive T cell. It is now ready to leave your thymus and it will be stored mainly in your lymph nodes to await an infection.

Now that your cytotoxic T (CD8) cell has been made, it waits in your lymph node for an infection. A dendritic cell (remember these guys? they are present all over your body) will come in through an afferent lymphatic vessel from the source of infection. An important feature of cytotoxic T cells is that it targets cytoplasmic infection, or more specifically viruses. Generally viruses proliferate within a cell and antibodies cannot get to them if the virus is residing inside one of your own cells. So the dendritic cell gets infected and travels through the afferent lymphatic vessel into your lymph nodes. Here waits all of your adaptive immunity responses. It's an ambush! Your cytotoxic cells have been waiting for this moment. The cytotoxic cell that is specific for the antigen that is presented on the dendritic cell latches on. There are two signals that activate the cytotoxic (CD8) cell. B7 from the dendritic cell attaches to CD28 on the cytotoxic T cell and CD8 attaches to the dendritic cell. The cytotoxic cell is now activated and it is now on a mission to destroy. It secretes IL-2 which binds to itself. This is an autocrine function that signals the cytotoxic cell to replicate like crazy. Your army travels out through the efferent lymphatic vessel into your blood stream. Eventually it arrives to the cells that are infected. It is capable of binding to the same antigens that it first recognized from the dendritic cell that brought it inside initially. It latches on with CD8 and releases its' weapons. Perforin is released which punches holes into the cell and granzymes are also released which induces apoptosis (cell death). Memory T cells are also made to fight against future infection. These are long lasting cells. Your other T cells (remember them?) the helper T cells come by and deactivate your cytotoxic T cells with FasR and CTLA-4.

Hope that helps.

Answer 2

Cytotoxic T cells function to identify and destroy infected or abnormal cells in the body. They do this by releasing toxic chemicals that cause cell death, effectively eliminating the threat to the immune system.

Answer 3

Cytotoxic T (or CD8) cells are activated in your lymph nodes by dendritic cells. Once activated they are sent out to the site of infection and they bind to the cells that express the MHC class I that are presenting the foreign antigen. They will then release perforin (punch holes in the infected cell) and granzymes (induces apoptosis). The infected cells are now destroyed. Memory cells are made at this point for future protection and FasR & CTLA-4 is released from the helper T cells to disable the cytotoxic T cells.

There are two different kinds of helper T cells. Th1 and Th2. Th1 functions to empower macrophages so that they can destroy intravesicular pathogens (bacteria). This is done by two signals. Binding of CD40L from Th1 to CD40LR on the macrophage and by interferon gamma released from Th1.

Th2 cells function to activate B cells. Normally it is insufficient for an antigen alone to stimulate the B cell to activation. The Th2 cell when activated will bind to the B cell (CD40L and CD40LR) and release cytokines, primarily IL-4, IL5 and IL-10. This will now activate the B cell into proliferation so that it can send out antibodies against that pathogen.

Answer 4

A T-cell is a type of blood cell. T-cells belong to a group of white blood cells (WBCs) called lymphocytes. WBCs protect the body from infection.

The main job of T-cells is to fight infection. There are a number of different types of T-cells that act in many ways to identify, directly attack and destroy infectious agents. Along with other WBCs, they play a major role in the immune system, which guards the body against infection.

After they are produced in the bone marrow, these cells spend some time maturing and developing in an organ in the chest called the thymus (why they are named T-cells). After maturation, T-cells are present in the blood and in lymph nodes.

T-cells may be affected in diseases of the immune system, like AIDS, and in cancers, like lymphoma.

Answer 5

Helper T (Th) cells in themselves do not fight disease and without help of other immune cells are basically deemed useless against infection. Helper T cells Activate and navigate other very important immune cells that do fight against infection, in a sense they are like the director of the lymphocytes. Yet, their is a class of T cells (cytotoxic T cells, Regulatory T cells, and Natural killer T cells) which are T cells, but not HELPER T CELLS. Overall, helper T cells are essential in determining B cell antibody class switching, activation and growth of cytotoxic T cells(which do fight infections), and maximizing the bacterial activity of phagocytes(macrophages).

Answer 6

These are the main cells of the Immune system. B cells create antibodies, which attach themselves to the pathogen and disable it. Killer T Cells do exactly what their name describes: they kill cells that have become infected by viruses.

Answer 7

T cells come in many different varieties, but the well-known are CD4+ T cells (helper T cells) and CD8+ T cells (cytotoxic T cells, or killer T cells). Central BioHub supports global immunological research by collecting cytology samples, precisely T cell samples, from healthy donors and patients with immune disorders, cancers, etc. Hurry up, order online.

Answer 8

T cells contribute to immune defenses in two ways. Some direct and regulate immune responses. Others directly attack infected or cancerous cells.

Answer 9

a helper t cell acts as a compliment cell, ultimately amplifying the effects of other b cell functions in the humoral anitbody response.

Answer 10

two types of t cell t nd b which r more commnly known as white blood cell