Immuno - Quiz 1 Review

drraythe's version from 2015-06-14 22:59


Question Answer
How does innate immunity differ from acquired immunity?INNATE: inflammatory response, lacks memory, necessary immediate
ACQUIRED: Antigen driven, specific, has memory, slow
Cells involved in innate immunity?Neutrophils, Macrophages (monocytes), NK cells
What do neutrophils do?First & major phagocyte to respond to infxns. Numerous, short lived, rapidly exhausted.
What do macrophages do?Long lifespan, maintained phagocytosis
What do NK cells do?Kill virally infected cells/ tumor cells
What receptors do neutrophils express?Fc receptors, complement protein receptors, integrin receptors (integrins also expressed), receptors for cytokines (monocytes also make cytokines), pattern recognition receptors
What receptors do NK cells express?Fc receptors, compliment protein receptors
What receptors do macrophages express?Fc receptors, complement protein receptors, integrin receptors (integrins also expressed), receptors for cytokines (monocytes also make cytokines), pattern recognition receptors
How do neutrophils & macrophages recognize microbes?PRRs (pattern recognition receptors) TLR (toll like receptors-- a type of PRR) allow them to see the PAMP (pathogen associated membrane patterns)
How do NK cells recognize virally infected & tumor cells?If a self-cell does not show the MHC-1 receptor, the NK will attack it. Also recognizes proteins expressed by cells undergoing stress
Fact...what is it, what does it do?Fc receptor is a receptor on a phagocyte, the portion that the Fc part of the antibody attaches to. Allows Fact-holding cell to know that it should phagocytize what the antibody is attached to
CR (compliment receptor) what is it, what does it doReceptors for complement proteins, which are group of serum + cell surface proteins that can be activated by immune system to trigger events
What are adhesion molecules?A type of integrin which allows neutrophils to attach to endothelium & move into tissues
What is TLR? What does it do?TLR: Toll like receptor, a type of PRR (pattern recognition receptor) which recognizes PAMPs (pathogen associated membrane patterns), which signal the cell to phagocytize the microbe
What did the BLAD case demonstrate?How important adhesion molecules (integrins) are. If the neutrophil cant migrate to the tissue, it can't be defended
Examples of passive immunityAntibodies in colostrum. Injecting antibodies or cytotoxic T-lymphocytes
What is HRIG, when is it used & why?Human rabies immunoglobulin. Injected so the acquired immune system can work more quickly if pt. has been exposed & was not vaccinated, because the acquired immune system is slow to create antibodies
Post exposure treatment for rabies if never vaccinatedInjected w/ HRIG (human rabies immunoglobulin) & the antigen injection
Post exposure treatment for rabies in previously vaccinated personAlready have antibody. Standard antigen shots given.
What is an immunogen?Antigen which causes an immune response
What is an antigen?Foreign molecule capable of binding w/ an immune component: "An antigen is a substance capable, under appropriate conditions, of inducing a SPECIFIC immune response (i.e. an acquire immune response)"
What is an epitope?That portion of the immunogenic molecule which actually binds w/ antibody or the TCR or the BCR. The TCR, BCR & Antibody do not recognize the entire immunogenic molecule. Instead, they only recognize a discrete site called the epitope. Can be proteins or not
What molecules can bind antigen?Antibody, T-cell receptor (TCR), B-cell receptor (BCR), & MHC molecules
Exogenous antigenExogenous antigen: Antigen made by the pathogen outside any host cell
Endogenous antigenAntigen (usually protein) made by the intracellular pathogen inside a host cell (host cell is infected w/ the pathogen)
Extracellular microbeExtracellular pathogens: Most bacteria & most parasites… (But not all). These microbes replicate outside of the host cell
Intracellular microbeViruses & some bacteria. Please note that viruses & obligate intracellular bacteria will exist outside a host cell prior to infecting it. But they need to be inside the host cell in order to replicate
Exogenous/endogenous refers to...Where the antigens are made
Intracellular/extracellular refers to...Where the microbes replicate
Humoral immunity steps (activation phase)ACTIVATION PHASE:
1) Macrophage engulfs antigen into a phagosome
2) Phagosome fuses w/ lysosome, antigen broken down (antigen processing)
3) Processed antigen combined w/ MHCII protein & displayed on cell membrane (antigen presentation)
4) Helper-T cell (CD4) binds to MHCII+antigen, macrophage releases cytokines to activate helper T
5) Helper-T now releases its own cytokins to make itself proliferate (all specific clones of receptor it has for MHCII+antigen)
Humoral immunity steps (effector phase)EFFECTOR PHASE:
1) B-cell w/ receptors specific for same antigen as engulfed by macrophage bind its receptors to the antigen & engulfs it (receptor mediated endocytosis)
2) Vesicle w/ antigen fuses w/ lysosome, antigen is processed. Antigen is attached to MHCII receptor & displayed on B-cell membrane
3) Helper-T cell that was cloned in activation phase binds to MHC-antigen displayed on B-cell. T-cell recognizes it & releases cytokines to stimulate B-cell to divide & clone itself
4) B-cells clone into memory cells or to antibody secreting PLASMA cells. Plasma cells produce many antibodies (identical to the surface receptor of the B-cell). Antibodies will bind & inactivate the original antigen
Cell-mediated immunity steps (activation phase)ACTIVATION:
1) Antigen enters a body cell, infected cell breaks down some of the antigens(viruses) proteins & attaches them to a MHCI protein, which is then displayed on cell's membrane
2) Cytotoxic T-cell binds to MHCI-antigen & T-cell is activated, which causes it to clone itself (& its specific antigen receptor)
Cell-mediated immunity steps (effector phase)EFFECTOR PHASE:
1) Cytotoxic T-cell clones go to encounter other infected cells w/ same MHCI-antigen presented & bind to them
2) When bound, T-cell releases perforin, which lyses the cells plasma membrane.
What cells are APCs?B-cells, Dendritic cells, Macrophages
MHC I for which immunity/ lymphocyteCell mediated immunity (T-cells)
MHC II for which immunity/ lymphocyteHumoral immunity (B-cells)
Criteria for a good antigen?>1000 Daltons, complex molecular structure (no highly repetitious chains), *foreign to body* (lipids & nucleic acids poor antigens, lipopolysaccharides are good antigens) & stable structures (wont degrade too quickly to find)
What is a hapten?Small molecules that are antigenic (for example can bind to antibody in a test tube) but are not immunogenic in vivo alone (do not elicit antibody production or any immune response) unless bound to a carrier protein
Which MHC for endogenous?MHC-I (cell mediated)
Which MHC for exogenous?MHC-II (humoral)
Dendritic cells deal w/ what MHC?MHC-II
What is 1⁰ immune response, what is involved in it?When an antigen is presented to a naive T-cell (only dendritic cells can do this)
Why do we have MHCs?T-cell cannot "see" an antigen until in the context of the MHC
What is MHC restriction?Antigen fragments can only trigger an immune response if they are bound to a **self** MHC molecule.
MHC genetic diversity...discussThe MHC gene region is highly polymorphic. i.e. there are a large number of alleles that code for the amino acid sequences that make up the variable region. Thus, the cells in each animal will be able to express a number of different MHC molecules (~ 200,000 different ones) & thus be able to present a wide variety of antigens to its immune system
MHC differences between individuals?Except for identical twins... the exact epitopes that the MHC molecules present to the T-lymphocytes will differ from 1 individual to another… Some epitopes presented will be the same, but the entire repertoire of epitopes presented will differ from 1 animal to the next.
Which cells can process endogenous antigen & present it through MHC-I… & which cells can then recognize antigen being presented by MHC-I?Any infected cell, & cytotoxic T-cells
Which cells can process exogenous antigen & present it through MHC-II… & which cells can then recognize antigen being presented by MHC-II?APCs & helper-T cells (followed by B-cells)
What is cross-presentation of antigen? What does cross-presentation of antigen accomplish?Under some circumstances exogenous antigens may enter the endogenous antigen pathway & thus be presented via MHC-I to CTLs. This may be important in immunity to viruses, since it implies that the antigens from DEAD virions that are engulfed by the APC may still be able to trigger a CTL response (CMI response). A CTL response will be needed in order to kill virally-infected cells
What kind of MHCs can an APC present?Exogenous & endogenous at the same time, potentially
Why is MHC genetic diversity important?If no variation, all individuals are equally susceptible to an antigen - this could potentially wipe out an entire population
What is an antibody?An antibody (Ab), also known as an immunoglobulin (Ig), is a large Y-shaped protein produced by B cells that is used by the immune system to identify & neutralize foreign objects such as bacteria & viruses
What cells make antibodies?B-cells
Fab region is?Portion of antibody (top of "Y") which attaches to an antigen at the epitope
Fc region is?Binds to Fc receptors on self-cells (neutrophils, macrophages, NKs)
Cross-reactivity of an antibody is?Identical or similar epitopes may sometimes be found on apparently unrelated molecules. As a result, antibodies directed against 1 antigen may react unexpectedly w/ an unrelated antigen (but 1 that has a very similar epitope)
Fc receptors on what cells?B lymphocytes, dendritic cells, natural killer cells, macrophages, neutrophils, & (mast cells)
T-cell maturation?All T-cells come from the bone & mature in the thymus. At thymus they divide rapidly. TCR gene rearrangement occurs. T-cells “learn” to only “see” antigen in the context of self-MHC. Survivors remain in thymus ~4-5 days before leaving to colonize the 2⁰ lymphoid organs & circulate in the blood. During this time they mature & express CD3 (all T cells) & either CD4 or CD8 molecules on their surface. Thus, T-cells that leave the thymus: CD3+/CD4+ population & CD3+/CD8+ population
T-cell selection- negative?Thymocytes (T-cell precursors) interact w/ dendritic cells which present self-antigens. Thymocytes w/ TCR that bind self-antigens receive a signal to die by apoptosis (95-99% of the thymocytes)
T-cell selection- positive?Thymocytes that survive the negative selection process are positively selected (don’t die) if they can recognize self- MHC molecules & have weak or no recognition of self-antigens. They leave the thymus as mature T-cells & colonize the 2⁰ lymphoid organs & circulate in the blood.
TCR =T-cell receptor, antigen binding receptor on a T-cell
How do T-cells see an antigen?In the context of an MHC molecule
T-cells activated by...Encountering MHC+antigen complex
What do CD4 T-cells do?Helper cells. Interact w/ MHC-II in humoral immunity, interact w/ B-cells
What do CD8 T-cells do?Killer/cytotoxic T-cells. Interact w/ MHC-I in cell-mediated immunity. Lyse infected cells.
Maturation of B-cells?In birds, the bursa. In mammals, peyers patches/bone. Formed in bone.
Selection of B-cellsProliferation & gene rearrangement for BCR repertoire generation. Negative selection of self-reactive B-cells. Mature B cells migrate to 2⁰ lymphoid tissues & circulate in the blood
How do B-cells recognize & respond to antigen? How B cell ‘see’ antigen?BCRs recognize antigen by their epitopes, ingest & degrade antigen, attach antigen to MCH-II receptor & place it on its cell membrane.
What can B-cells do?Make antibodies, memory cells, semi-professional APCs, (phagocytize).
BCR vs antibody?Identical, the antibody just isnt attached to the cell membrane
What is humoral immunityB-lymphocytes the main player…make antibody (Ab) Antibody targets invaders that are outside of cells… Thus, target EXTRACELLULAR bacteria; viruses before they get into cells, etc
What is CMI?Cell mediated immunity. T-lymphocytes are the main players in CMI. CMI targets cells that are infected w/ INTRACELLULAR pathogens
Sources of lymphocytes… the stem cells they arise fromPluripotent stem cell → lymphoid stem cell
1⁰ lymphoid organs? What happens in them?1⁰ = Sites of lymphocyte development. Thymus, bursa, peyers patches, bone marrow
2⁰ lymphoid organs? What happens here?2⁰ = Sites where lymphocytes respond to antigen. Tonsils, spleen, lymph nodes, peyers patches
How do innate/ acquired immune system communicate w/ each other?Via APCs, cytokines..
What causes tissue rejection?Foreign MHC molecules (esp. MHC-I since there are on all cells)
What are CDs?Clusters of differentiation...differentiate different lymphocytes
What antigens can be immunogenic from bacteria?Lipopolysaccharides & peptidoglycans
How specific are MHCs?They have broad specificity (1 MHC can display many different similar-ish types of antigen, but only 1 at a time)