What Is a Cytotoxic T Cell?

Cytotoxic T cells (Tc or CTL), also known as killer T cells. A cell that monitors and kills target cells when needed. Memory cytotoxic T cells have a memory function for target cells with antigens and are differentiated from cytotoxic T cells. Once target cells with specific antigens are found, they will stimulate effector cytotoxic T cells to produce effector cytotoxic T cells and destroy infected cells or cancer cells.

Cytotoxic T cells (CTL) lyse target cells infected by the virus by secreting perforin, and can also connect to Fas on the surface of infected target cells by expressing the death gene product Fas ligand (Fas-L) , Trigger the intrinsic apoptosis mechanism of target cells, leading to target cell apoptosis. People with CTL dysfunction will have recurrent and severe infections, such as chickenpox, herpes virus, and cytomegalovirus infections, and other intracellular microorganisms such as pneumocystis carinii and tuberculosis. BCG vaccination in these patients can cause lung and systemic mycobacterial infections ^[1]

Cytotoxic T cells: Most cytotoxic T cells are

T cells, but a few are

cell. There are two main cytolytic mechanisms of cytotoxic T cells:

secretory,

Dependence mechanism.

non-secretory,

Independent mechanism. Participate in rejection during transplantation ^[2]

For influenza virus infection, both antibodies and CTL are involved in the anti-infective immune response. After influenza virus vaccination, anti-influenza virus neuraminidase antibodies and hemagglutinin are related to the ability to prevent the disease. Passive immunity can prevent pneumonia in experimental mice, but rhinitis and bronchitis cannot be avoided unless specific IgA is given at the same time. However, recovery from influenza virus infection depends on the role of specific CTLs. Animal experiments show that adoptive transfer to specific CTL can clear the virus in athymic mice infected with influenza virus, and specific antibodies can also shorten the virus discharge time, but it is not as fast as transfer to specific CTL. Part of the cause of severe illness in elderly influenza patients may be related to the decline in age-related CTL activity ^[1]

The amount of antibody immune response and cellular immune response in anti-virus infection immunity varies with different virus infections; even if the same virus is infected, the immune response is also different due to the host's immune response ability and the amount of exposed virus.

The following two examples are sufficient to illustrate the problem: recurrent chickenpox can be seen in patients with high serum antibody levels but their cellular immune function is suppressed; and administration of chickenpox zoster immune serum treatment in patients with T-cell immune deficiency can prevent the occurrence or reduction of disease Condition ^[1] .