Chapter 21: T cells
Terms in this set (26)
What are the functions of helper T cells?
-Plays a central role in adaptive immune response
-Activate both humoral and cellular arms
-Once primed by APC presentation of antigens, they help activate T and B cells, induce T and B cell proliferation, their cytokines recruit other immune cells
-Amplifies the immune response of the innate immune system
-Activate macrophages (more potent killers)
-Mobilize lymphocytes and macrophages, and attract other types of WBCs
What happens if there are no helper T cells?
-No immune response
What is the first step that the helper T cells do in order to activate B cells?
-Helper T cells binds with the self-nonself complexes of the B cells that has encountered its antigen and is displaying it on MHC II on its surface
-Interact directly with B cells displaying antigen fragments bound to MHC II receptors
What is the second step that helper T cells do in order to activate B cells?
-Helper T cells releases interleukins as co-stimulatory signals to complete B cell activation
-Stimulate B cells to divide more rapidly and begin antibody formation
Can B cells be activated without a helper T cell?
-Yes, can bind to T cell-independent antigens
-Response is weak and short lived
What are T cell-dependent antigens?
-T cells that activate B cells
What is the first step in CD8 cell activation?
-Helper T cell binds to dendritic cells
-CD8 cells require helper T cell activation into destructive cytotoxic T cells
-Causes dendritic T cells to express co-stimulatory molecules required for CD8 cell activation
What is the second step in CD8 cell activation?
-Helper T cell stimulates the dendritic cells to express co-stimulatory molecules
What is the third step in CD8 cell activation?
-Dendritic cells can now activate CD8 cell with the help of interleukin 2 secreted by T cells
What are cytotoxic T cells?
-Directly attacks and kills other cells
-Activated T cells circulate in blood, lymph, and lymphoid organs in search of body cells displaying antigens they recognize
How do cytotoxic T cells destroy infected or abnormal cells?
-Cytotoxic T cells binds specific membrane receptors on target cells, and stimulates apoptosis
-Cytotoxic T cells releases perforins and granzymes by exocytosis (perforins create pores through which granzymes enter target cells: granzymes stimulate apoptosis)
What is the first step of a cytotoxic T cell destroying an infected cell?
-Cytotoxic T cell identifies foreign antigens on MCH I proteins and binds tightly to target cell
What is the second step of a cytotoxic T cell destroying an infected cell?
-Cytotoxic T cells releases perforin and granzymes molecules from its granules by exocytosis
What is the third step of a cytotoxic T cell destroying an infected cell?
-Perforin molecules insert into the target membranes, polymerize, and form transmembrane pores (cylindrical holes) similar to those produced by complement activation
What is the fourth step of a cytotoxic T cell destroying an infected cell?
-Granzymes enter target cells via the pores
-Once inside, granzymes activate enzymes that trigger apoptosis
What is the fifth step of a cytotoxic T cell destroying an infected cell?
-Cytotoxic T cell detaches and searches for another prey
What is AIDS?
-Acquired Immune Deficiency Syndrome
How is AIDS caused?
-Caused by human immunodeficiency virus (HIV)
How is HIV caused?
-Can enter the body through blood transfusions, blood contaminated needles, sexual intercourse and oral sex, mother to fetus
What does AIDS do to the body?
-Cripples the immune system by interfering with the function of helper T cells
What are the symptoms once AIDS cripples the immune system?
-Virus also invades the brain -> dementia
How is AIDS treated?
What is the general definition of an autoimmune disease?
-The immune system loses ability to distinguish between self and nonself
What happens when someone has an autoimmune disease?
-Production of autoantibodies and sensitized helper T cells that destroy the body tissues
What are some examples or types of autoimmune diseases?
-Type 1 diabetes
What is the treatment for autoimmune diseases?
-Suppress the entire immune system