actions of natural killer cells and cytotoxic T cells – Flashcards

-T cells that display CD4. -aka CD4 T cells. -inactive (resting). -recognize exogenous antigen fragments associated with major histocompatibility complex class II. (MHC II)

1. interacts with APC (antigenic recognition), 2. costimulation occurs.

The first signal in T cell activation is antigen binding to a TCR; the second signal is a costimulator, such as a cytokine or another pair of plasma membrane molecules.

-or CD8 T cells -recognize foreign antigens combined with major histocompatibility complex class I (MHC I) molecules on the surface of : 1. body cells infected by microbes. 2. some tumor cells. 3. cells of tissue transplant. -

-recognition requires the TCR and CD8 protein to maintain the coupling with MHC I. (antigenic recognition) -costimulation by interleuken-2 or other cytokines produced by active helper T cells that have already becomes bound to copies of the same antigen.

presentation of antigen associated with both MHC I and MHC II molecules.

The CD8 protein of a cytotoxic T cell binds to the MHC‐I molecule of an infected body cell to help anchor the T cell receptor (TCR)-antigen interaction so that antigen recognition can occur.

-do not attack infected body cells. - quickly proliferate and differentiate into more active cytotoxic T cells and more memory cytotoxic T cells if the same antigen enters the body another time.

-soldiers. -cell mediated immune responses. -leave secondary lymphatic organs and tissues and migrate to seek out and destroy infected target cells, cancer cells, and transplanted cells. -attach to these target cells and kill them.

Cytotoxic T cells attack some tumor cells and transplanted tissue cells, as well as cells infected by microbes.

-cytotoxic T cells have receptors specific for a particular microbe and thus kill only target body cells infected with one particular type of microbe. -natural killer cells can destroy a wide variety of microbe‐infected body cells

1. using receptors on their surfaces, recognize and bind to infected target cells that have microbial antigens displayed on their surface. -releases granzymes, protein‐digesting enzymes that trigger apoptosis. -Once the infected cell is destroyed, the released microbes are killed by phagocytes. 2. bind to infected body cells and release two proteins from their granules: perforin(bursts the cells) and granulysin (create holes) and lymphotoxin (enzymes).

-inserts into the plasma membrane of the target cell and creates channels in the membrane. -As a result, extracellular fluid flows into the target cell and cytolysis (cell bursting) occurs.

-granules in cytotoxic T cells release granulysin, which enters through the channels and destroys the microbes by creating holes in their plasma membranes.

-a toxic molecule, which activates enzymes in the target cell. -These enzymes cause the target cell's DNA to fragment and the cell dies.