Sloma.Immune System I And II_Practice Questions

2.

Immunodeficienies can be caused by defects in expression of many different molecules that contribute to both adaptive and innate immune responses. Failure to express which molecule would have no effect on the immune system’s ability to eliminate an extracellular bacterium?

MHC class I
MHC class II
Surface‐bound antibody molecules
Toll‐like receptors
Complement components

Correct Answer

A. MHC class I

Explanation

A : Without MHC class II, antigen presenting cells cannot present exogenously‐derived antigen to CD4
T cells, thus preventing a CD4 T cell response against the extracellular bacterium. Without surfacebound
antibody molecules, B cells cannot get activated and there would be no antibody production
against the antigen. Without antibody production, there would be diminished phagocytosis of the
antigen by phagocytes and no classical complement activation to eliminate the pathogen. Without Tolllike
receptors, macrophages and dendritic cells would have decreased recognition of the antigen;
consequently, there would be no killing by the macrophage and very little antigen presentation of the
antigen to CD4 T cells. Without the complement components, there would be reduced inflammation at
the site of infection, no direct killing of the pathogen via the complement pathway, and no opsonization
of the pathogen by complement components (reduced pathogen uptake by phagocytes).

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3.

Your patient, a 7 month‐old boy, is suffering from repeated ear infections. In the lab, you determine that he has a defect in B cell function. What is the most likely defect?

Inability to synthesize toxic nitric oxides
Failure to produce complement components
Failure to express toll‐like receptors
Failure to express MHC class I molecules
Failure to express surface‐bound antibody molecules

Correct Answer

A. Failure to express surface‐bound antibody molecules

Explanation

E: Without surface‐bound antibody expression, a B cell cannot become activated. Surface‐bound
antibody molecules serve as the antigen‐recognition receptor for B cells.

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4.

How do macrophages play an important role in the elimination of pathogens?

Produce complement proteins that can eliminate the pathogen
Phagocytosis of pathogens followed by presentation of antigens to B cells
Phagocytosis of pathogens followed by oxygen‐dependent and oxygen‐independent killing of the pathogen
Produce antibody molecules that can mark the pathogen for destruction
Phagocytosis of pathogens followed by formation of the membrane‐attack complex that causes lysis of pathogens

Correct Answer

A. Phagocytosis of pathogens followed by oxygen‐dependent and oxygen‐independent killing of the pathogen

Explanation

C NOTE: The membrane attack complex is formed by the activation of complement…this is a detail
about complement activation that I don’t expect you to know for now…

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5.

Antigen presenting cells are essential in contributing to the activation of T cells. How do they accomplish this?

They use MHC class I and class II molecules to present peptide antigens to T cells
They use MHC class I and class II molecules to present carbohydrate antigens to T cells
They secrete complement proteins that activate T cells
They present antigen:antibody complexes to T cells
They trigger activation of T cells through Toll‐like receptors

Correct Answer

A. They use MHC class I and class II molecules to present peptide antigens to T cells

Explanation

A : This question is simply asking about how T cells recognize antigen and what type of antigens they
can recognize.

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6.

What type of pathogen would be processed and loaded into MHC class II molecules?

Antigens from a parasite that infects endothelial cells
Antigens from a virus infecting endothelial cells
Antigens from a bacterium infecting endothelial cells
Antigens from extracellular bacteria
Antigens from bacteria that infects endothelial cells

Correct Answer

A. Antigens from extracellular bacteria

Explanation

D : This question relies on the recognition that MHC class II molecules present exogenously‐derived
antigens. In all answer choices except D the cell is infecting a cell that does not express MHC class II.

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Sloma.Immune System I And Ii_practice Questions

Which of the following is not a direct consequence of antibody binding to antigen?

Quiz Preview

Immunodeficienies can be caused by defects in expression of many different molecules that contribute to both adaptive and innate immune responses. Failure to express which molecule would have no effect on the immune system’s ability to eliminate an extracellular bacterium?

Your patient, a 7 month‐old boy, is suffering from repeated ear infections. In the lab, you determine that he has a defect in B cell function. What is the most likely defect?

How do macrophages play an important role in the elimination of pathogens?

Antigen presenting cells are essential in contributing to the activation of T cells. How do they accomplish this?

What type of pathogen would be processed and loaded into MHC class II molecules?