Lecture Set 6 : Part 4 Flashcards
what are the professional antigen presenting cells?
-macrophages
-dendritic cells
-B cells
what is the purpose of professional antigen presenting cells? how do they do this?
-engulf foreign material and break it apart
-present it on the surface to other cells of the immune system (T cells)
-antigens must be presented along with the major histocompatibility complex
what is the major histocompatibility complex?
-self antigen
-classes I and II
what is MHC class I?
-found on all nucleated body cells (all cells except RBC
-identifies the cells as self (self-antigen)
-allows cells to present endogenous antigens to cytotoxic T cells
-if the cytotoxic T cell recognizes the antigen as foreign it will be activated to destroy cells that display that antigen
-natural killer cells look for cells with MHC I
what are endogenous antigens?
-antigens that come from inside the cell
what does it mean if a cell doesn’t have MHC I?
-same as presenting an antigen
-shows that the cell is not self
-infection has occurred
what is MHC class II?
-found only on professional antigen presenting cells (dendritic cells, macrophages, and B cells)
-present exogenous antigens to T helper cells
-if the T helper cell recognizes the antigen as foreign it will be activated to help other components of immunity prepare a response
what are exogenous antigens?
-antigens that were originally outside the cell but taken up by phagocytosis
is an immune response developed every time an exogenous antigen is presented to a T helper cell?
-NO
-sometimes cells can take in things that are no harm to the cell
what are the characteristics of T helper cells role in the immune system?
-each T helper cell has T-cell receptors for one specific antigen
-the antigen must be presented to it by an antigen presenting cell with MHC II (only the correct antigen will activate it)
-the T helper cells will then differentiate into subsets
-some differentiate into cells that recruit other cell types and others differentiate into memory T helper cells
-CD4+ cells
what is beginning of the humoral (antibody mediated) response before the B cell is activated?
-begins when a B cell encounters a foreign antigen
-each B cell has receptors for one specific antigen (surface molecule of IgD)
-binding of that antigen to the receptor causes the B cell to ingest and break down the intruder
-presents the antigen to a T helper cell with MHC II
what is the process of the humoral (antibody mediated) response once the B cell is activated?
-if the antigen fits into the T helper cell’s TCR, the T helper cell secretes cytokines to activate the B cell
-the B cell will undergo clonal selection and expansion (multiples and differentiates into 2 cell types)
what 2 cell types does the activated B cell differentiate into after clonal selection and during clonal expansion?
-plasma cells
-memory B cells
what are plasma cells?
-short lived B cells that secrete large amount of antibody (factories)
-travel through the blood and tissue to deal with the pathogen
what are memory B cells?
-much fewer of these made compared to plasma cells
-long lived cells that maintain memory of the pathogen
-if they encounter the pathogen again, they can respond quickly by producing a new generation of plasma cells
how does the primary response differ from the secondary response in terms of antibody production?
-primary response has a lag time of days to weeks (B cells need time to be activated)
-first antibody produced is IgM, followed by IgG
-major outcome is the production of memory B cells
-secondary response has no lag period (acts rapidly)
-memory B cells are already available and can differentiate into plasma cells
-produce large amounts of IgG
-result is that the infection is quickly overcome or non-existent (response outpaces the antigen’s ability to divide)
what is the purpose of vaccines in terms of the primary and secondary response?
-vaccine is trying to get you through the primary response so that when you encounter the real pathogen, you get a quicker and better response
what is the beginning of the cell mediated response before the cytotoxic T cell is activated?
-begins when an infected antigen presenting cell processes and presents an endogenous antigen along with MHC I
-the presented antigen contacts the cytotoxic T cell’s T-cell receptor
what cell leads the cell mediated response?
-cytotoxic T cells (CD8+ cells)
-each has a T-cell receptor for one specific antigen that binds with MHC I
what is the process of the cell mediated response once the cytotoxic T cell is activated?
-if the antigen matches the TCR, then the cytotoxic T cell is activated
-the cytotoxic T cell then divides and differentiates into 2 cell types
what 2 cell types does the activated cytotoxic T cell differentiate into?
-memory cytotoxic T cells
-effector cytotoxic T cells
what do the effector cytotoxic T cells further differentiate into? what is its beginning process?
-further activated by a T helper cell which causes it to become a cytotoxic T lymphocyte (CTL)
-CTL circulates in blood and tissues and searches for other body cells that present that specific antigen along with MHC I
what happens when the cytotoxic T lymphocyte finds a body cell with the specific antigen and the MHC I?
-secretes perforins and granzymes which destory the abnormal or infected cell
what are perforins?
-enzymes that poke holes in the infected cell’s membrane
