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Microbiology Test 3
Specific Immune Defenses
what are the two main branches of specific immune defenses?
1. antibody- mediated immunity
2. cell- mediated immunity
what do both branches have in common?
they are antigen- specific meaning they are antibody generating
what is an antigen?
any compound, usually large and complex, that is foreign/non-self and stimulates both branches and stimulates both branches of specific immune system
what are the chemical structures of antigens?
any compound as long as it is foreign usually large and complex such as proteins, nucleic acids, lipids, and carbs
which type of antigen is the most likely to be structurally complex?
proteins, they create the best response from our defenses
where do antigens come from?
what are the two types of antigens?
1. cell- bounded (attached to pathogen)
2. soluble/free- floating (released from pathogen)
what is a cell bound antigen?
compunds that are foreign and are attached to surface of the pathogen such as part of the cell wall, flagella, pili, etc
what are soluble antigens?
compunds that are seperated from the pathogen such as endotoxins, fragments of lysed pathogens
antigens may be found in what two places?
what are extracellular antigens?
antigens that are not able to enter host cells, circulate in blood, lymphatic system, interstitial spaces
what are intracellular antigens?
antigens that enters host cells
is an endotoxin and extracellular or intracellular antigen?
is an exotoxin an extracellular or intracellular antigen?
why can a virus be both an intracellular and extracellular antigen?
the are extracellular before they enter a host cell
does the specific immune system go after one unique pathogen or toxin?
no, one pathogen may have many antigens
do cells only recognize one antigen of one pathogen?
no, each antigen has multiple epitopes
what is an epitope?
different regions of the antigen that each stimulate an independent specific immune response
what does it mean by immune system cells are antigen- specific?
cells of specific immune system are only able to recognize one epitope of one antigen
what happens when there are more epitopes?
there is a greater response from the immune system
does the specific immune system respond to all antigens, regardless of their chemical structure, origin, or location?
how does antibody- mediated immunity provide protection?
by WBCs called B lymphocytes
when can a receptor bind to one epitope of one antigen in antibody mediated immunity?
once mature B cells display their 10K- 100K receptors on surface
where do mature B cells circulate?
blood, lymph, migrate to lymph nodes, spleen, and wait for antigen to arrive
what happens when an antigen arrives during antibody- mediated immunity?
it binds to receptors causing activation of B cell
what happens when B cells are activated?
it causes the cell to divide to form many clone cells
what are the two types of clone cells?
1. plasma cells
2. memory B cells
what are plasma cells?
they are the most abundant and make and secrete antibodies 2000/sec for 4-5 days than they die
does every antibody recognize and bind to the same epitope as original B cell?
what are memory B cells?
long-lived, remain in body and wait for same antigen to return in the future it it does it will mount a stronger, faster, longer lasting response
why do vaccination works?
because of memory B cells
what are the four things antibodies do?
4. lysis by complement fixation
what is neutralization?
antibody coat the surface of antigens so that they are unable to interact-with host cells, they are inactivated
what happens when the antigen is inactivated?
there is no harm to the host
what type of action causes soluble antigens to clump together?
what type of action causes cell-bound antigens to clump together?
what does neutralization, precipitation, and agglutination all have in common?
they all opsonize the antigen and enhance phagocytosis
what does C3a do?
finds a basophil to stimulate histamine release and enhance inflammation
what does C3b do?
opsonized leading to phagocytosis and stimulates MAC insertion leading to lysis
what are antobodies not capable of doing?
entering host cells, so they are only effective against extracellular antigens
what does cell-mediated immunity provide protection against?
how does cell-mediated immunity provide protection?
by WBCs call T lymphocytes
what do mature T cells display?
receptors on surface with double recognition
what is double recognition?
receptors simultaneousley recognize:
1. one epitope of one antigen
2. the host cell MHC ("self")
what activates the T cell?
when a problematic host cell is found
what are the four types of clone cells for T lymphocytes?
1. cytotoxic T cell
2. Helper T cell
3. Suppressor T cell
4. Memory T cell
how does a cytotoxic T cell kill the host?
1. secrete perforins causing lysis
2. secrete lymphotoxins causing degredation of host DNA
3. secrete tumor necrosis which causing apoptosis (cell suicide)
what type of T cell stimulates actions/ proliferations of other T cells and B cells?
helper T cells
what type of T cell inhibits further actions of T and B cells once antigen/pathogen is gone?
supressor T cells
what does a memory T cell do?
it is long-lived, wait for antogen to return, if it does it will mount a faster, stronger, longer lasting response
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