Immunology After Class Quizzes Flashcards
What is an antigen?
Any molecules that can induce a specific adaptive immune response
Molecules such as proteins, nucleic acids, polysaccharides, metals can induce cells of the adaptive immune response (T or B cells) to be activated.
What immunological phenomenon is mediated by the adaptive immunity?
Killing of infected cells by T cells
The adaptive immunity involves cytotoxic T cells that can kill infected cells. It also involves Thelper cells that can activate macrophages that have ingested microbes.
What is the characteristics of naive and memory cells?
Naive cells survive for weeks while memory cells survive for years
Naive cells are short lived and will die without encountering an antigen. Memory cells survive for years without encountering an antigen and can respond immediately when re-encountering an antigen.
What is the function of the lymphatic system?
Allows antigens to accumulate in lymph node
The lymphatic system is the sewer of the body and allows lymph to drain in the lymph nodes where antigens can accumulate and dendritic cells can pick them up.
Your patient has been recovering from implant surgery at home and get an infection. He lives 2 hrs from an hospital and drives there to get an iv antibiotic treatment. Which immune deficiency would have the best outcome. since he appears to be lacking?
T and B cells
Since neutrophils and monocytes are required to control the infection early on. the best outcome for this patient would be to only have a defect in B and T cells.
A gum infection is occurring. What is the first step by which cells of the innate immunity identify that microbes have invaded the gum?
They express receptors with limited diversity allowing them to recognize molecules expressed by microbes.
Cells of the innate immunity express receptors with limited diversity and are therefore not very specific.
What is the most important function of the innate immunity at early time-points (days) following a bacterial infection?
Controlling the levels of infection until the adaptive immunity is activated.
Controlling the levels of bacterial infection until the adaptive immunity is activated is the main function of the innate immunity.
What is the main function of NK cells?
Killing infected cells
NK cells kill cells that are infected with microbes via production of perforin and granzyme.
Innate Immunity (in three words):
Immediate, non-specific, no memory
The characteristics associated with the innate immunity are immediate response, lack of specificity, and no memory as phagocytes can ingest microbes immediately to kill them. The characteristics associated with the adaptive immunity are delayed response, specificity, memory as it takes 14 days to activate sufficient numbers of TIB cells
Adaptive immunity: (in three words):
Delayed, specific, memory
The characteristics associated with the innate immunity are immediate response, lack of specificity, and no memory as phagocytes can ingest microbes immediately to kill them. The characteristics associated with the adaptive immunity are delayed response, specificity, memory as it takes 14 days to activate sufficient numbers of TIB cells
What role do liver-produced acute phase reactant proteins play during an infection?
They mediate phagocytosis by opsonizing the microbe
Liver-produced acute phase reactants are opsonins and mediate microbe phagocytosis via its opsonization
(lagging It Tor ingestion)
How do innate cells mediate inflammation, i.e., identified by swelling, redness, heat & pain, upon infection?
They produce molecules that affect other cells
Innate cells produce soluble molecules such as cytokines and histamine upon an infection that increase vascular permeability and attract and activate other cells, leading to inflammation.
What are the systemic effects of inflammatory cytokines released upon an infection?
They induce fever, mobilize neutrophils from the bone marrow and induce production of acute phase
reactants.
(Cytokines have several systemic effects including induction of fever and acute phase reactants and
mobilization or neutrophils)
What are the sequential steps that lead to recruitment of leukocytes at the site of an infection?
Upregulation or adhesion molecules-activation or integrin-stable adhesion-migration through endothelium
(For recruitment of leukocvtes to occur. endothelial cells must upreaulate adhesion molecules that allow
Feedback
leukocytes to attach weakly. Integrin on the surface or leukocytes are then activated by chemokines and stable adhesion occurs that leads to migration of the leukocytes through the interendothelial space.)
What is the apropriate characteristic of MHC?
Proteins
MHC molecules only bind protein antigens, i.e., peptides.
What is the apropriate characteristic of MHC class I?
Alpha chain/beta2-microglobulin/CD8
MHC I molecules are composed of an alpha chain and beta-microglobulin and bind to CD8.
What is the apropriate characteristic of MHC class II?
Alpha and beta chains/CD4
MHC II molecules are composed of an alpha chain and a beta chain and bind to CD4.
How are endocytosed extracellular proteins processed for presentation to T cells?
Processed in the endosome/lysosome and loaded onto MHC Class II for presentation to CD4 T cells.
Endocytosed extracellular proteins are processed in the endosome/lysosome and loaded onto MHC Class II for presentation to CD4 T cells.
What statement concerning antigen presentation is correct?
CD4 T cells recognize peptides associated with MHC class II.
CD4 T cells recognize only peptides presented on MHC class II molecules.
What statement below reflects accurately antigen presentation?
DC present antigen bound to MHC molecules to T cells.
Antigen must be bound to MHC molecules on DC to be presented to TCR on the surface of T cells.
What is the function of Th17 cells in response to infection?
Th17 cells help recruit neutrophils to the mucosa for clearance of extracellular microbes.
IL-17 produced by Th17 cells induce chemokines from other cells/tissues that in turn mediate trecruitment of neutrophils at the mucosa that ingest extracellular microbes and kill them.
How do activated cytotoxic T cells (CTL) kill cells infected with an intracellular microbe?
CTL are activated by DC and receive help from Thelper cells to produce perforin and granzyme which lyse infected cells.
CTL will be reactivated by recognizing their target cells via the interaction of their TCR with the antigen-MHCI complex, and will produce perforin and granzyme. Thelper cells will produce cytokines that help with their activation and differentiation.
Match the T cells with the cytokines they produce: Th17
produce IL-17 and IL-22.
Match the T cells with the cytokines they produce: Th2
produce IL-4 and IL-5
Match the T cells with the cytokines they produce: Th1
produce IFNγ
Cytokines produced by DC and other innate cells determine the fate of naive T cells and the cytokine they will produce. What cytokines accurately induce Th cell differentiation?
IL-4 induces Th2
What signals are provided by Thelper cells to help macrophages and B cells?
CD40L and IFNgamma
Thelper cells provide help to B cells and macrophages so they can mediate their function, i.e., make antibodies and kill ingested microbes. One signal is provided by the ligation of CD40 on B cells and macrophages to CD40L on T cells. Cytokines produced by T cells such as IFN gamma is also required to activate macrophages, and induce isotype switching from IgM to IgG for B cells.
What is the difference between naive and effector T cells in a situation in which there is an infection?
Effector T cells contract following clearance of pathogens.
Naive T cells have never encountered an antigen. Once they are activated they become effector T cells that proliferate and mediate their function, e.g., fight an infection. Once the pathogen is cleared, most of the effector T cells are being eliminated, i.e., contraction.
Match the different molecules with their ligands and cells: CD28
B7-APC
CD28 is on T cells and binds to B7 on APC.
Match the different molecules with their ligands and cells: CD40L
CD40-APC
CD40L is on T cells and binds to CD40 on APC.
Match the different molecules with their ligands and cells: MHC-I
TCR-CD8
MHCI binds to CD8 on T cells.
Match the different molecules with their ligands and cells: MHC-II
TCR-CD4
MHCII binds to CD4 on T cells.
Match the different molecules with their ligands and cells: IL-2
IL-2R-T cells
IL-2 binds to IL-2R on T cells.
What is necessary for maturation of thymocytes?
Expression of preTCR and TCR
Expression of preTCR and TCR determines the ability of T cells to survive in the thymus and mature.
How does BCR diversity able to reach 10^11?
Random recombination of gene segments and removal/addition of nucleotides.
Recombination of gene segments is random but diversity only reaches 10^6. Removal and addition of nucleotides allow receptor diversity to be as high as 10^11.
What are the critical steps involved in the positive selection of B cells in the bone marrow?
Expression of pre-BCR and IgM
Immature B cells need to express sequentially pre-BCR then IgM to receive survival signals, pass the two maturation checkpoints and be positively selected.
Immunoglobulins possess several functions. Which function listed below is not one of them?
Antibodies induce production of toxic molecules by neutrophils that kill the microbes.
Antibodies do not induce production of toxic molecules by neutrophils.
What happen when Fcγ receptors on innate cells bind the Fc portion of IgG bound to microbial molecules expressed by infected cells?
Antibody dependent cell mediated cytotoxicity is triggered.
Antibodies can recognize microbe molecules on infected cells and binding of the Fc portion to Fc gamma receptor on the surface of NK cells triggers their activation and degranulation for killing of the infected cells.
What are the main differences of the 3 complement pathways?
The 3 complement pathways are triggered by different events and their C3 convertases will be composed of different molecules, i.e., C3bBb for the alternative pathway and C4b2a for the classical and lectin pathways.
What is the main difference of the immune response triggered by extracellular bacteria versus intracellular bacteria?
T cell-mediated immunity is absolutely required for clearance of intracellular bacteria not extracellular bacteria.
T cell-mediated immunity is required for clearance of intracellular bacteria but not for clearance of extracellular bacteria. For infection by intracellular bacteria that are located in the vesicles, Th1 cells are required to activate macrophages via CD40-CD40L and IFNgamma-IFNgammaR for killing of the microbes in the phagolysosome. For intracellular bacteria that have escaped in the cytosol, CD8 CTL are required to lyse the infected cells via perforin/granzyme and eliminate the bacterial reservoir.
Althouth viruses are obligate intracellular pathogens, the immune response elicited is different compared to intracellular bacteria. Chose the correct statement characterizing the immune response against virus.
Viruses induce a strong production of IFNα that induces an antiviral state.
Upon infection with a virus, production of IFNα is produced first to induce a viral state, i.e., inhibits virus replication.
Match the pathogens with the appropriate cells of immune response and outcome: intracellular bacteria
Th1-activation of macrophages
Intracellular bacteria elicit Th1 cell differentiation that leads to activation of macrophages.
Match the pathogens with the appropriate cells of immune response and outcome: virus
IFNα−inhibition of viral replication
Viruses elicit IFNα that leads to inhibition of viral replication.
Match the pathogens with the appropriate cells of immune response and outcome: helminth
Th2-eosinophils
Helminths elicit Th2 cell differentiation that leads to eosinophil degranulation.
Match the pathogens with the appropriate cells of immune response and outcome: extracellular fungus
Th17-neutrophils
Extracellular fungus elicit Th17 cell differentiation that leads to recruitment of neutrophils.
Which of the following factors is the first to be secreted upon mast cell activation?
Histamine
Histamine is stored into granules and released immediately when mast cells are activated and degranulate.
Penicillin cannot elicit an immune response on its own, but can elicit an immune response if coupled to a carrier protein. It is then referred to as a:
Hapten
When a molecule is not capable of eliciting an immune response on its own but can when coupled to a protein, it is called an hapten.
Which of the following would likely lead to a decrease in CD4 cells only?
Defect in MHC Class II expression
Defect in MHC class II expression would have an impact on CD4 T cells not CD8 T cells.
Which of the following mechanisms describes how autoantibodies can kill self cells in a Type II Hypersensitivity response that results in autoimmune disease?
Autoantibody-mediated opsonization and phagocytosis of self cells.
Type II hypersensitivity involves antibodies recognizing self antigen that mediate opsonization and phagocytosis of host cells leading to their destruction.
What are the characteristics of autoimmunity?
Immune cells mount an immune response against self-antigens.
Autoimmune diseases develop when the immune cells recognize self-antigens as foreign and develop an immune response against those antigens.
Which of the following causes of cancer has been responsible for the very large increase in oral cancers over the last 10+ years?
HPV infection
HPV has been responsible for the very large increase in oral cancers over the last 10years.
What statement accurately reflects the properties of tumor immunity?
Tumor can evade the immune response.
Although one role of the immune response is to eliminate tumor cells, tumor cells can evade the immune response by producing immunosuppressive factors (TGFbeta, IL-10) and recruiting inhibitory immune cells such as Tregs or MDSCs.
Match the terms associated with B cell characteristics appropriately: Isotype switching
Cytokines
Cytokines produced by Tfh will signal B cells to switch the isotype of produced Ig from IgM to IgG, IgE or IgA.
Match the terms associated with B cell characteristics appropriately: Affinity maturation
Point mutations
Affinity maturation occurs in the germinal centers and occurs through through point mutations in the variable regions, resulting in B cells processing high affinity antigen receptors
Match the terms associated with B cell characteristics appropriately: Hypervariable regions
Antigen-binding site
Hypervariable regions exhibit the strongest binding-sites for antigen
Match the terms associated with B cell characteristics appropriately: Plasma cells
Antibody secretion
