Exam 1: Review

Question 1

You are part of a research team that is attempting to design a better vaccine for the prevention of tuberculosis, which is caused by the intracellular bacterial pathogen Mycobacterium tuberculosis. You are considering to include an adjuvant, a substance which enhances the body’s immune response to an antigen, in the vaccine formulation. Which one of the following would be a reasonable choice of an adjuvant component?

A. A cytokine that promotes an IFN-γ response to mycobacterial Ags
B. The complement peptide C3a, which will ensure adequate phagocytosis.
C. Interleukin-10
D. Bacterial lipopolysaccharide
E. Lactoferrin

Answer 1

A. A cytokine that promotes an IFN-γ response to mycobacterial Ags

Question 2

A common strategy, called antigenic variation, is used by bacteria to evade an immune attack and killing. Antigenic variation involves mutations which change the structures of bacterial molecules so that microbes are no longer recognized by the immune system. This strategy, most likely allows evasion of which type of immune recognition?

A. Toll-like receptor-dependent recognition of microbes by cells of the innate immune system
B. Mannose receptor-dependent recognition of microbes by cells of the innate immune system
C. Antibody-dependent recognition of microbial cell surface molecules D. Natural killer cell inhibitory receptor recognition of class I MHC
molecules on infected cells
E. T cell receptor recognition of microbial cell wall lipid antigens

Answer 2

C. Antibody-dependent recognition of microbial cell surface molecules D. Natural killer cell inhibitory receptor recognition of class I MHC

Question 3

A 7-year-old boy who cut his finger about 20 hours ago presents to the emergency department with localized reactions such as redness, swollenness, and pain. What is the cause of the observed clinical manifestations in this patient?

A. CD4 T lymphocytes
B. CD8 T lymphocytes
C. CD4 and CD8 lymphocytes
D. Cytokine-mediated inflammation
E. Ab-mediated bacterial killing

Answer 3

D. Cytokine-mediated inflammation

Question 4

Damage-associated molecular patterns (DAMPs), also known as alarmins, are molecules released by stressed cells undergoing necrosis that act as endogenous danger signals to promote and exacerbate the inflammatory response. Which of the following molecules is released from a necrotic cell and recognized as a danger signal by the immune system?

A. C3b component of complement
B. C-reactive protein
C. HMGB1 (High Mobility Group Box 1)
D. RAGE (Receptor for Advanced Glycosylation End products)
E. Ubiquitin

Answer 4

C. HMGB1 (High Mobility Group Box 1)

Question 5

Extracellular bacterial pathogens do not invade cells. Instead, they proliferate in the extracellular environment which is enriched with body fluids. Some of extracellular bacteria even don’t penetrate body tissues (e.g. Vibrio cholerae) but adhere to epithelial surfaces and cause disease by secreting potent toxins. If patient has an infection caused by an extracellular bacteria, which cells of adaptive immunity are the most important in defense against this infection?

A. Neutrophils
B. CD8+ T cells
C. Eosinophils
D. NK cells
E. B cells

Answer 5

E. B cells

Question 6

A 31-year-old female presents to the hospital with abdominal cellulitis, fevers, and chills. Relevant history includes poorly controlled insulin-dependent diabetes (type-1 diabetes) with progressive renal failure and blindness. As a result of the renal problems, she required peritoneal dialysis which was complicated by multiple infections at the catheter site. Which cytokine has a potent chemoattractant activity on immune cells which strongly involved in resolution of skin infection?

A. IL-1 
B. IL-2 
C. IL-4 
D. IL-6 
E. IL-8

Answer 6

E. IL-8

Question 7

The C3a is produced by an enzymatic cascade that activates the complement. What is the major functional role of this byproduct in immuno-inflammatory reactions mediated by complement?

A. Formation of C3 convertase
B. Promoting phagocytosis
C. Triggering the alternative-pathway of complement activation 
D. Formation of C5 convertase
E. Promoting chemotaxis of immune cells

Answer 7

E. Promoting chemotaxis of immune cells

Question 8

Complement component 3 deficiency is a rare, genetic, primary immunodeficiency characterized by susceptibility to infection due to extremely low C3 plasma levels. Patients with C3 component deficiency have a history of which of the following?

A. Increased numbers of severe viral infections
B. Increased numbers of severe bacterial infections with extracellular bacteria
C. Increased numbers of severe bacterial infections with intracellular bacteria
D. Frequent episodes of hemolytic anemia
E. Increased risk of anaphylactic reactions

Answer 8

B. Increased numbers of severe bacterial infections with extracellular bacteria

Question 9

A 55-year-old man with multiple primary liver abscesses caused by Escherichia coli has a fever and shaking chills. Which causes the symptoms of septic shock in the patient?

A. Associated abscess in the hypothalamus
B. Hypothalamic response to leukocytosis
C. Leukocyte inflammation of the hypothalamus
D. Release of fragments of damaged hepatocytes into the circulation
E. Release of IL-1 and TNF into the circulation

Answer 9

E. Release of IL-1 and TNF into the circulation

Question 10

Complement is an important component of the innate immune system that is crucial for defense from microbial infections and for clearance of immune complexes and injured cells. In normal conditions complement is tightly controlled by a number of fluid-phase and cell surface proteins to avoid injury to autologous tissues. When complement is hyperactivated, as occurs in autoimmune diseases or in subjects with dysfunctional regulatory proteins, it drives a severe inflammatory response in numerous organs. What triggers the decay of C1 component upon the classical activation of complement?

A. Bacterial antigens
B. Factor B
C. Antigen-IgG complexes
D. Bacterial lipopolysaccharides 
E. Mannose-binding lectin

Answer 10

C. Antigen-IgG complexes

Question 11

Soil-transmitted helminth infections are caused by different species of parasitic worms. They are transmitted by eggs present in human feces, which contaminate the soil in areas where sanitation is poor. Approximately 1.5 billion people are infected with soil-transmitted helminths worldwide. Which of the following types of cells are notable for their presence at the sites of helminth infections?

A. Cytotoxic T cells
B. Eosinophils
C. B lymphocytes
D. Monocytes
E. Neutrophils

Answer 11

B. Eosinophils

Question 12

Three days ago, an otherwise healthy 17-year-old boy sustained a skin laceration during a lacrosse match. Yesterday, he complained of mild “flu-like” symptoms. This morning, he became suddenly ill with a fever, general muscle aches, and dizziness; then he lost consciousness. On arrival in the emergency department, he had a temperature of 37.8°C and a heart rate of 136 beats per minute. His blood leukocyte count was 22,000 cells per mcl (reference range: 4,500 to 1 2,500 per mcl). The predominant cell type(s) in this patient’s blood is/are most likely

A. B lymphocytes.
B. juvenile and mature neutrophils.
C. monocytes and macrophages.
D. natural killer cells.
E. T lymphocytes.

Answer 12

B. juvenile and mature neutrophils.

Question 13

Electron microscopy studies showed the presence of the membrane attack complex (MAC) on the surface of isolated non-necrotic muscle fibers, indicating a role for complement activation in genetically inherited Muscular Dystrophies. The susceptibility to complement-mediated damage is due to lack of the complement regulatory protein that is active in the cell membrane. Malfunctioning which of the following complement components is most likely the causative factor in the pathogenic mechanisms of the disease?

A. Properdin 
B. Factor I 
C. Factor B 
D. C1q 
E. Factor D

Answer 13

B. Factor I

Question 14

Mannose-binding lectin (MBL) is a pattern recognition molecule of the innate immune system. MBL lectin (carbohydrate-recognition) domain is found in association with collagenous structure. Which of the following is not a characteristic of mannose-binding lectin?

A. acts as an opsonin by binding to mannose-containing carbohydrates of pathogens
B. synthesized by hepatocytes
C. induced by elevated IL-6
D. a member of the collectin family
E. triggers the alternative pathway of complement activation

Answer 14

E. triggers the alternative pathway of complement activation

Question 15

Defensins are small (29-35 amino acids) proteins produced by circulating white blood cells and epithelial cells. Defensins have broad-spectrum activity against gram-positive and gram-negative bacteria and kill bacteria in a number of ways. Which of the following does not describe defensins?

A. highly conserved with few variants
B. contain a large proportion of arginine residues
C. contain three interchain disulfide bonds
D. amphipathic, with hydrophobic and hydrophilic regions
E. disrupt pathogen membranes by penetrating and disrupting their integrity

Answer 15

C. contain three interchain disulfide bonds

Question 16

The function of MHC molecules is to bind peptide fragments derived from pathogens and display them on the cell surface for recognition by the appropriate T cells. The consequences are almost always deleterious to the pathogen – virus-infected cells are killed, macrophages are activated to kill bacteria living in their intracellular vesicles, and B cells are activated to produce antibodies that eliminate or neutralize extracellular pathogens. All the following are characteristics of both MHC class I and II molecules except:

A. They are expressed codominantly.
B. They are expressed constitutively on all nucleated cells.
C. They are glycosylated polypeptides with domain structure.
D. They are involved in presentation of antigen fragments to T cells.
E. They are ex pressed on the surface membrane of B cells.

Answer 16

B. They are expressed constitutively on all nucleated cells.

Question 17

MHC class I deficiency is a rare autosomal recessive disease also known as Bare lymphocyte syndrome type I. Patients with severely decreased MHC class I expression have the most severe phenotype and present with a combined immunodeficiency in the first year of life with bacterial, fungal, and parasitic infections. MHC class I molecules are important for which of the following?

A. binding to CD8 molecules on T cells
B. presenting exogenous Ags (e.g., bacterial protein) to B cells
C. presenting intact viral proteins to T cells
D. binding to CD4 molecules on T cells
E. binding to Ig on B cells

Answer 17

A. binding to CD8 molecules on T cells

Question 18

Hepatitis B is a viral infection that attacks the liver and can cause both acute and chronic disease. The virus is transmitted through contact with the blood or other body fluids of an infected person. After Hepatitis B virus infects liver cells, which of the following about the processing and presentation of virus- derived proteins is correct?

A. All the peptides derived from the processing associate with his HLA class I molecules.
B. Processing occurs exclusively in acid vesicles.
C. The virus-derived peptides that bind to his HLA class I molecules also bind to his sister’s HLA class I molecules.
D. Some virus-derived peptides are presented to CD8+ T cells.
E. His HLA class T molecules preferentially bind virus-derived peptides 15-20 amino acids long.

Answer 18

D. Some virus-derived peptides are presented to CD8+ T cells.

Question 19

B cell development and differentiation occurs in multiple phases. The initial, Ag-independent phase generates mature B cells that can bind to a unique non-self Ags. This stage of development occurs in the bone marrow. The Ag- dependent phase of B cell development occurs following B cell activation by Ag binding and co-stimulation. Which of the following is expressed on the surface of the mature B lymphocyte?

A. CD40
B. MHC class II molecules
C. MHC class I molecules
D. IgMandIgD
E. all of the above

Answer 19

E. all of the above

Question 20

T cell differentiation and maturation is a tightly regulated process during which T cell precursors undergo rearrangement and expression of TCRs followed by elimination of self-reactive thymocytes. Which of the following statements concerning T-cell development is correct?

A. Progenitor T cells that enter the thymus from the bone marrow have already rearranged their TCR genes.
B. Interaction with thymic nonlymphoid epithelial cells is critical.
C. Maturation in the thymus requires the presence of foreign antigen.
D. MHC class II molecules are not involved for elimination of self- reactive T cells
E. MHC class I molecules are not involved for elimination of self- reactive T cells.

Answer 20

B. Interaction with thymic nonlymphoid epithelial cells is critical.

Question 21

The immune system has a near limitless capacity for detecting abnormalities (danger signals). This remarkable ability for self-interrogation is achieved by the related structures of two molecules, antibodies (B cell receptors) and T cell receptors. The TCR, a defining structure of T cells, is a transmembrane heterodimer that recognizes only protein Ags presented as MHC-Ag complexes on Ag-presenting cells. Which of the following statements is incorrect concerning Ag-specific receptors on T cells?

A. They are clonally distributed transmembrane molecules.
B. They have extensive cytoplasmic domains that interact with intracellular signaling molecules.
C. They consist of polypeptides with variable and constant regions.
D. They are associated with signal transduction molecules at the cell surface.
E. They can interact with peptides derived from nonself-Ags

Answer 21

B. They have extensive cytoplasmic domains that interact with intracellular signaling molecules.

Question 22

A 30-year-old female is admitted to the emergency room with a recurrent viral infection. Blood work shows normal numbers of circulating B cells, T cells, monocytes, and neutrophils in her blood. A deficiency in production which of the following cytokines may contribute to clinical condition of this patient?

A. IL-2 
B. IL-5 
C. IL-4 
D. TGF-β 
E. IL-10

Answer 22

A. IL-2

Question 23

Johnny is a 1-month-old healthy child who has not, as yet, received any childhood immunizations. He presents with his first episode of otitis media (middle ear infection) that is successfully treated with a 3-week course of antibiotics. Which one of the following immune components contributed the most to his clearing the infectious agent during the first few days of his infection?

A. BCRs on his B lymphocytes
B. TLRs on his neutrophils
C. Cytokines that promoted Ab formation 
D. T cell responses to bacterial Ags 
E. Memory B cells

Answer 23

B. TLRs on his neutrophils

Question 24

The pathogenesis of anaerobic infections includes disruption of the mucosal surface and entry of the anaerobic bacteria with the invasion of the deep tissue. The mechanisms of entry of anaerobic bacteria may include local trauma, surgery, appendicitis, and tissue necrosis. If neutrophils are recruited to an anaerobic site to kill such a bacterium, which of the following substances would will be used?

A. IL-12
B. Nitric oxide
C. Interferon-α
D. Respiratory burst oxidase
E. Cathelicidin

Answer 24

E. Cathelicidin