Immunology After Class Quizzes

Question 1

What is an antigen?

Answer 1

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.

Question 2

What immunological phenomenon is mediated by the adaptive immunity?

Answer 2

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.

Question 3

What is the characteristics of naive and memory cells?

Answer 3

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.

Question 4

What is the function of the lymphatic system?

Answer 4

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.

Question 5

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?

Answer 5

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.

Question 6

A gum infection is occurring. What is the first step by which cells of the innate immunity identify that microbes have invaded the gum?

Answer 6

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.

Question 7

What is the most important function of the innate immunity at early time-points (days) following a bacterial infection?

Answer 7

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.

Question 8

What is the main function of NK cells?

Answer 8

Killing infected cells

NK cells kill cells that are infected with microbes via production of perforin and granzyme.

Question 9

Innate Immunity (in three words):

Answer 9

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

Question 10

Adaptive immunity: (in three words):

Answer 10

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

Question 11

What role do liver-produced acute phase reactant proteins play during an infection?

Answer 11

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)

Question 12

How do innate cells mediate inflammation, i.e., identified by swelling, redness, heat & pain, upon infection?

Answer 12

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.

Question 13

What are the systemic effects of inflammatory cytokines released upon an infection?

Answer 13

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)

Question 14

What are the sequential steps that lead to recruitment of leukocytes at the site of an infection?

Answer 14

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.)

Question 15

What is the apropriate characteristic of MHC?

Answer 15

Proteins

MHC molecules only bind protein antigens, i.e., peptides.

Question 16

What is the apropriate characteristic of MHC class I?

Answer 16

Alpha chain/beta2-microglobulin/CD8

MHC I molecules are composed of an alpha chain and beta-microglobulin and bind to CD8.

Question 17

What is the apropriate characteristic of MHC class II?

Answer 17

Alpha and beta chains/CD4

MHC II molecules are composed of an alpha chain and a beta chain and bind to CD4.

Question 18

How are endocytosed extracellular proteins processed for presentation to T cells?

Answer 18

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.

Question 19

What statement concerning antigen presentation is correct?

Answer 19

CD4 T cells recognize peptides associated with MHC class II.

CD4 T cells recognize only peptides presented on MHC class II molecules.

Question 20

What statement below reflects accurately antigen presentation?

Answer 20

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.

Question 21

What is the function of Th17 cells in response to infection?

Answer 21

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.

Question 22

How do activated cytotoxic T cells (CTL) kill cells infected with an intracellular microbe?

Answer 22

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.

Question 23

Match the T cells with the cytokines they produce: Th17

Answer 23

produce IL-17 and IL-22.

Question 24

Match the T cells with the cytokines they produce: Th2

Answer 24

produce IL-4 and IL-5

Question 25

Match the T cells with the cytokines they produce: Th1

Answer 25

produce IFNγ

Question 26

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?

Answer 26

IL-4 induces Th2

Question 27

What signals are provided by Thelper cells to help macrophages and B cells?

Answer 27

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.

Question 28

What is the difference between naive and effector T cells in a situation in which there is an infection?

Answer 28

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.

Question 29

Match the different molecules with their ligands and cells: CD28

Answer 29

B7-APC

CD28 is on T cells and binds to B7 on APC.

Question 30

Match the different molecules with their ligands and cells: CD40L

Answer 30

CD40-APC

CD40L is on T cells and binds to CD40 on APC.

Question 31

Match the different molecules with their ligands and cells: MHC-I

Answer 31

TCR-CD8

MHCI binds to CD8 on T cells.

Question 32

Match the different molecules with their ligands and cells: MHC-II

Answer 32

TCR-CD4

MHCII binds to CD4 on T cells.

Question 33

Match the different molecules with their ligands and cells: IL-2

Answer 33

IL-2R-T cells

IL-2 binds to IL-2R on T cells.

Question 34

What is necessary for maturation of thymocytes?

Answer 34

Expression of preTCR and TCR

Expression of preTCR and TCR determines the ability of T cells to survive in the thymus and mature.

Question 35

How does BCR diversity able to reach 10^11?

Answer 35

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.

Question 36

What are the critical steps involved in the positive selection of B cells in the bone marrow?

Answer 36

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.

Question 37

Immunoglobulins possess several functions. Which function listed below is not one of them?

Answer 37

Antibodies induce production of toxic molecules by neutrophils that kill the microbes.

Antibodies do not induce production of toxic molecules by neutrophils.

Question 38

What happen when Fcγ receptors on innate cells bind the Fc portion of IgG bound to microbial molecules expressed by infected cells?

Answer 38

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.

Question 39

What are the main differences of the 3 complement pathways?

Answer 39

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.

Question 40

What is the main difference of the immune response triggered by extracellular bacteria versus intracellular bacteria?

Answer 40

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.

Question 41

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.

Answer 41

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.

Question 42

Match the pathogens with the appropriate cells of immune response and outcome: intracellular bacteria

Answer 42

Th1-activation of macrophages

Intracellular bacteria elicit Th1 cell differentiation that leads to activation of macrophages.

Question 43

Match the pathogens with the appropriate cells of immune response and outcome: virus

Answer 43

IFNα−inhibition of viral replication

Viruses elicit IFNα that leads to inhibition of viral replication.

Question 44

Match the pathogens with the appropriate cells of immune response and outcome: helminth

Answer 44

Th2-eosinophils

Helminths elicit Th2 cell differentiation that leads to eosinophil degranulation.

Question 45

Match the pathogens with the appropriate cells of immune response and outcome: extracellular fungus

Answer 45

Th17-neutrophils

Extracellular fungus elicit Th17 cell differentiation that leads to recruitment of neutrophils.

Question 46

Which of the following factors is the first to be secreted upon mast cell activation?

Answer 46

Histamine

Histamine is stored into granules and released immediately when mast cells are activated and degranulate.

Question 47

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:

Answer 47

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.

Question 48

Which of the following would likely lead to a decrease in CD4 cells only?

Answer 48

Defect in MHC Class II expression

Defect in MHC class II expression would have an impact on CD4 T cells not CD8 T cells.

Question 49

Which of the following mechanisms describes how autoantibodies can kill self cells in a Type II Hypersensitivity response that results in autoimmune disease?

Answer 49

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.

Question 50

What are the characteristics of autoimmunity?

Answer 50

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.

Question 51

Which of the following causes of cancer has been responsible for the very large increase in oral cancers over the last 10+ years?

Answer 51

HPV infection

HPV has been responsible for the very large increase in oral cancers over the last 10years.

Question 52

What statement accurately reflects the properties of tumor immunity?

Answer 52

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.

Question 53

Match the terms associated with B cell characteristics appropriately: Isotype switching

Answer 53

Cytokines

Cytokines produced by Tfh will signal B cells to switch the isotype of produced Ig from IgM to IgG, IgE or IgA.

Question 54

Match the terms associated with B cell characteristics appropriately: Affinity maturation

Answer 54

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

Question 55

Match the terms associated with B cell characteristics appropriately: Hypervariable regions

Answer 55

Antigen-binding site

Hypervariable regions exhibit the strongest binding-sites for antigen

Question 56

Match the terms associated with B cell characteristics appropriately: Plasma cells

Answer 56

Antibody secretion