Exam 2- Antibodies and the memory response Flashcards
antibodies are (definition)
secreted immunoglobin proteins
secreted antibodies react with antigens where
extracellular spaces
structure of antibodies
heterodimer with 2 light chains (22kda) and 2 heavy chains (55kda) joined by a disulfide bridge; variable ends are the first 110 a.a. of amino terminal (specificity)
variable region of antibody
110 a.a. on amino-terminal of both chains
VDJ
generates Ig diversity; makeup the variable region
Part that determines the class of antibody
constant region-binds the immune cells (macrophages) and reacts with complements
Antibody Function
circulate blood seaking target antigen, find, bind, and mark for destruction(5 ways)
5 mechs of antibody function
Agglutination Fixes and activates complement Opsonization Neutralization Antibody dependent cell mediated cytotoxicity
Agglutination
crosslink antigen to reduce number of infectious units (clump)-able b/c 2 binding sites
Fixes and activates complement
activate complement via CLASSICAL pathway—–ab binds to antigen on pathogen and activates formation of C3 convertase to activate MAC and inflammation
antibodies activate complement via
classical pathway
Opsonization
coating antigen w/ antibody which enhances phagocytosis (IgG and C3B); Phagocytes have Fc receptor that binds IG (bound to antigen) causes phagocytosis
Fc receptor binds to
IgG on opsonized antigen for phagocytosis; or to Ab in the case of antibody dep. cell mediated cytotoxicity
Neutralization
blocks adhesion of bacteria and viruses to mucosa, blocks attachment of toxins (no longer can act on host cells)
Antibody dependent cell mediated cytotoxicity
target cells for destruction by eosinophils and NK cells——Eosinophils have Fc receptor that binds Ab, recognizing antigen on large pathogens (worms)— secretes perforin and granzyme; NKs can recognize Ab on antigens too!
target cells for destruction by eosinophils and NK cells
Antibody dependent cell mediated cytotoxicity
Number of different heavy chain constant regions
5 ISOTYPES
determines the Ig Class
the a.a. sequence in the constant region of the heavy chain
IgM structure
monomeric; secreted is pentameric
IgM function
expressed on B cells (BCR), Activates compliment, good at agglutination (can bind 10) and is first class produced in primary response
1st class of antibody produced in primary response
IgM
most abundant Ig in serum
IgG
Antibody that crosses placenta
IgG-very small
antibody involved in complement activation
IgG and IgM
Predominant class of antibody in secreations
IgA
Helps protect mucosal membranes/mucosal immunity
IgA
Antibody which exists as a dimer
IgA (secretory)
IgA
secreations, mucous membranes, J train across intestinal wall, dimer,
Antibody that is membrane bound on B cells (BCR) and not very present in serum
IgD
Very little present in serum
IgD
IgE
allergic reactions and worm infections
IgD
B cell membrane bound, little in serum
antibody for allergic reactions and worms
IgE
Class switching
increases number of functional antibodies without altering antigen specificity
Class switching progression
IgM initilal (agglutination) –> IgG (default-good for activating complement and therefor MAC to attack infection
IgM vs IgG
different classes, meaning different heavy chains, but same Fab region because they bind the SAME ANTIGEN
determines antibody class
heavy chain
determines antigen bound
Fab region
mechanism of class switching
enzymes delete regions of the constant region–no loss of DNA –> IgM
loss of DNA puts constant region first and –> IgG
Memory response
a larger population of sensatized plasma cells are ready to respond (already a few cells developed)
Memory B cells from primary response
differentiate into plasma cells w/o needing direct contact to the Th cell–NOTE antibodies made in secondary response are better
Types of Memory B cells
- Memory plasma cell-long lived plasma cell in BONE MARROW and secretes IgG (CLASS SWITCHED)–no T equivalent
- Normal, central memory B cells-reside in secondary lymphoid organs and proliferate slow to maintain pool of memory B cells–primed army for next infection and can replenish memory plasma cells
keeps B cell army available-reside in lymphoid organs
normal, central memory B cells
secrete IgG-reside in bone marrow
B memory plasma cells
Memory antibody characteristics
higher number and affinity in response, BCR also acquires mutations –> binds better
immunization
exposure to antigen
differentiate amt and rates of antibodies in primary and secondary responses
in 1: fast IgM;
IgG comes later and both die fast
in 2: fast IgM; IgG comes faster, stronger, longer
effect of secondary exposure on IgM
NONE!! responds fast and dies fast still, IgG is just faster, stronger, and longer
Cell mediated and humoral response on adaptive immunity
chosen branch is based on pathogen, humoral –> antibodies good at attacking extracellular
branch good at producing antibodies that attack extracellular things well
humoral
branch good at attacking intracellulars
cell mediated; producing helper T cells, activated macrophages and Cytotoxic T cells
best at clearing intracellular bacteria
macrophages
best at clearing viral infections
T cells
Kill intracellular org
must transform, phagocytize and MHCII presentation, antibody and complement
