ABIO335 Chapter 2
Which of the following are characteristics of complement receptor 1 (CR1)?
Correct = it is a receptor on the surface of macrophages, contains complement control protein (CCP) modules, facilitates phagocytosis, binds to C3b, inhibits complement fixation on the surface of macrophages Incorrect: binds to iC3b
Which of the following statements regarding platelets is correct?
Correct = platelets contribute to the formation of blood clots, secrete prostaglandins, participate in the coagulation system Incorrect = platelets secrete complement components, enhance vasodilation at infected sites
In which way is α2-macroglobulin similar to complement component C3?
Correct = α2-Macroglobulin contains an interior highly reactive thioester bond, must undergo a conformational change to carry out its function Incorrect = during infection, a2-macroglobulin is cleaved by the C3 convertased of C3bBb of the alternative pathway of complement activation, a2-macroglobulin spontaneously changes it conformation
Which of the following refers to monocytes that leave their circulation and take up residence in tissues?
macrophages
Much attention has been focused on developing synthetic antimicrobial peptides (AMPs) as alternatives to anti-infective therapies. Their therapeutic effectiveness, however, would have limitations in the long run because pathogens evolve ways of escaping the action of antimicrobial peptides.
True
Pentraxins provide the innate immune response with some of the same attributes that antibodies provide to the adaptive immune response.
True
T/F: Protein complexes containing α2-macroglobulin bound to proteases are removed using receptor-mediated uptake by macrophages, fibroblasts, and hepatocytes.
True
Antibodies bind more effectively to extracellular viruses than they do to intracellular viruses
True -- Antibodies are soluble, secreted molecules of the immune system that have access to viruses only in the extracellular stage of their life cycles.
In what way does Listeria monocytogenes differ from Streptococcus pneumoniae?
L. monocytogenes is an intracellular bacterium
_____ occurs when protein-coated pathogens are phagocytosed more effectively than uncoated pathogens.
Opsonization
The type of immune response required to eradicate listeriosis requires ______________________________.
killing of human cells in which the bacteria are living
Identify the mismatched pair.
kinin system: vasoconstriction
Individuals with a C3 deficiency would not be able to activate the alternative or lectin pathways of complement, but the classical pathway would still be intact.
False
What do many of the regulators of complement activation (RCAs) that ensure C3b is deposited on the surface of pathogens and not on the surfaces of healthy host cells and tissues contain?
Complement control protein (CCP) modules
What do the terminal complement proteins form?
Membrane-attack complex
identify the mismatch pair
decay-accelerating factor: inhibits C9 recruitment
What occurs when C3 is cleaved?
C3a and C3b are formed
Specialized epithelial cells of the small intestine called _____ secrete cryptdins.
Paneth cells
Which are mismatched? (1) Mechanical barrier: pulmonary surfactant (2) Mechanical barrier: tight junctions between epithelial cells (3) microbiological barrier: commensal microorganisms (4) chemical barrier: antimicrobial peptides (5) chemical barrier: acidic environment
(1) Mechanical barrier: pulmonary surfactant Reasoning: it's a chemical barrier
If 1 in 40 Japanese people are carriers of a nonfunctional C9 gene, then _____ homozygotes will be unable to form the membrane-attack complex of the three complement pathways.
1 in 1600
Why does the pathogen surface become heavily coated with C3b during the early steps of the alternative pathway of complement activation?
A positive-feedback mechanism promotes assembly of additional complexes of C3 convertase
Which cleave or do not cleave? (1) C3bBa (2) factor D (3) iC3bBb (4) C3bBb
Cleaves = 3, 4 Doesn't cleave = 1,2
Which of the following is a line of defense used by the immune system during infection?
Adaptive immune responses, immediate innate immune responses, induced innate immune responses
Which of the following occurs during an inflammatory response induced by complement activation?
All of the above -- mast cells and basophils degranulate, capillaries permeabilize, smooth muscles contract, blood vessels dilate
_____ is the general name given to a complement fragment produced during complement activation that facilitates inflammation at sites of infection.
Anaphylatoxins
_____ is (are) a collection of plasma proteins that act in a cascade of reactions to target extracellular forms of pathogens for engulfment by phagocytes or direct killing.
Complement
Which of the following refers to a protein that inhibits complement fixation on the surface of human cells?
Complement control protein
Identify the correct sequence that operates during the early steps of the alternative complement pathway.
C3 - iC3 - iC3Bb - C3b - C3bBb
_____ is the C5 convertase of the alternative pathway of complement activation.
C3b2Bb
Which components of the membrane-attack complex are the last that remain soluble?
C5b6
Which of the following do neutrophils and monocytes upregulate the expression of in response to the potent anaphylatoxin C5a?
CR1 and CR3
Which are true or false? (1) C3 often forms a covalent bond with water molecules (2) The hydrolysis of C3 is required for the initiation of the alternative pathway of complement activation (3) C3 undergoes spontaneous conformational changes that expose the sequestered thioesterbond (4) C3 is synthesized continuously by the pancreas (5) C3 is synthesized only after an infection begins
Correct = 1, 2, 3 Incorrect = 4, 5
Which of the following is not a characteristic of C3b?
Correct = It recruits phagocytes to sites of infection Incorrect = It contains a high-energy thioester bond subject to nucleophilic attack, it is inactive in the hydrolyzed form, it participates in complement fixation
Why do defensins provide more effective protection against microbes in some people than others?
Correct = There are genetic polymorphisms in genes that affect the amino acid composition and killing properties of defensins. There is genetic variation in the number of α- and β-defensin genes. Incorrect = they are produced constitutively in some individuals, and inducibly (after infection) in others, defensins kill only gram-negative bacteria so individuals infected by gram-positive bacteria are not afforded protection by defensins
Which of the following statements regarding complement is correct?
Correct = complement proteins are not activated until an infection develops Incorrect = Complement proteins are available only in the blood, are synthesized continuously by the spleen, inhibit phagocytosis
As a consequence of increased permeability and changes in cellular adherence properties, _____ are able to cross intact endothelium of blood vessels at sites of infection.
Correct = complement proteins, plasma proteins, monocytes, neutrophils Incorrect = erythrocytes
Which of the following would be inconsistent with clinical cases involving an immunodeficiency of factor I?
Correct = decreased levels of factor H in the blood, elevated levels of C3 in the blood Incorrect = increased susceptibility to infections caused by encapsulated bacteria, decreased ability to fix C3b on bacterial surfaces
Which of the following do not facilitate the cleavage and inactivation of C3b by factor I?
DAF
T/F: Defensins are synthesized only in the gastrointestinal tract, where they defend the body against ingested microbes.
False
Which of the following enhances the rate and power of complement activation?
Factor P
Complement control proteins must be membrane-bound to regulate complement fixation at the cell surface.
False
T/F Nucleophilic attack of the thioester bond of C3b by water is necessary before C3b can bind covalently to the surface of pathogens.
False
T/F: Animals born and raised in a sterile environment are healthier than animals raised in a germ-ridden environment?
False
T/F: Complement regulatory proteins inhibit complement pathway progression up to the formation of C5 convertase, but not after.
False
T/F: Once formed, iC3 binds to factor D and undergoes degradation.
False
T/F: Because all pathogens must gain entry into host cells to complete their life cycles, the only way to completely eradicate the pathogen during infection is to kill the infected cells
False -- Although some pathogens require entry into host cells to complete their life cycle, others do not. Therefore, mechanisms must be in place to recognize and destroy pathogens in extracellular spaces of infected tissues.
T/F: Following engulfment by macrophages, pathogens are degraded in phagosomes
False -- degradation occurs in the phagolysosome
T/F: Kupffer cells are resident phagocytes of the lungs.
False -- they're in the liver
Susceptibility to infection by which of the following increases due to deficiency in the terminal components of the complement pathway?
N. meningitidis
According to a review by Vanitha Janakiraman (Rev. Obstet. Gynecol. 2008, 1:179-185), infections caused by Listeria monocytogenes are about 20 times more common in pregnant women than in the general population, and account for 27% of all listerial infections. Infection during pregnancy, usually arising from ingestion of contaminated food such as soft cheeses, poses serious threats to the fetus including severe disease or death. Which of the following statements provides a plausible explanation for why pregnancy predisposes to infection by this bacterium?
The host defense required to combat intracellular bacteria such as L. monocytogenes is a cell-mediated process that kills infected cells; pregnancy reduces the efficacy of this type of immunity.
Which of the following statements regarding commensal microorganisms is true?
True = Antibiotics can alter the composition of commensal microorganisms permitting colonization of pathogenic bacteria, Before birth there are no commensal microorganisms living in or on the body False = Commensal microorganisms populate only the gastrointestinal tract and enter the body by ingestion, commensal microorganisms have an adverse effect on health
Indicate whether each of the following is true or false in reference to the function of mucosal epithelia.
True = they secrete antimicrobial substances; provide mechanical barriers to pathogens, provide chemical barriers to pathogens False = located only in the gut, are hostile environments for all microbes
When C3 and C5 are cleaved during complement activation, the smaller _____ fragments promote inflammation, whereas the larger _____ fragments participate in the next stage of the complement pathway.
a,b
The protein α2-macroglobulin has attracted the attention of clinicians as a supplementation therapy to treat osteoarthritis of the knee. Which of the following provides a rationale for the use of this naturally occurring glycoprotein to reduce pain in patients suffering from this crippling disease?
a2-macroglobulin binds to and traps enzymes including collagenase, which breaks down cartilage in the knee
[no question]
all are correct (coagulation system, kinin system, complement activation system) -- All three of these systems use enzymatic cascades involving plasma proteins.
The _____ pathway of complement activation begins immediately upon infection.
alternative
Imagine that you are working for a biotechnology company and have been assigned to develop a recombinant synthetic long pentraxin that will be used for therapeutic purposes. Which of the following will not be a characteristic of this biologic?
amphipathic proteins
When moving from an infected host cell to an uninfected host cell, Listeria monocytogenes ___
breaks through the membrane of the infected cell and the membrane of the neighboring cell to gain entry into the cytosol of the uninfected host cell
How do pentraxins function?
by binding to pathogens and phagocyte receptors
The only complement pathway that is part of both innate and adaptive immunity is the _____ pathway.
classical
A 32-year-old woman presented with a history of pneumococcal and meningococcal infections. After a prolonged stay in the intensive care unit for respiratory complications, her physician conducted tests to determine if she had an immunodeficiency. Screening tests confirmed that the classical complement pathway was functional, but not the alternative complement pathway. The activity of the alternative pathway was restored by mixing the patient's serum with properdin-deficient serum, but not with factor B-depleted serum. From this information, which of the following is consistent with the patient's repeated susceptibility to infections caused by encapsulated bacteria?
factor B deficiency
Unlike lysozyme, which kills bacteria by degrading their cell walls, defensins ______________________________.
forms pores in the membranes of bacteria that disrupt their integrity
The short pentraxins are made by _____, while the long pentraxins are made by _____.
heptocytes; myeloid, endothelial, and epithelial cells
The antimicrobial properties of defensins are due to ______________________________.
hydrophilic and hydrophobic regions that penetrate pathogen membranes and form pores
What does factor I generate when working together with factor H?
iC3b
A patient presents with the unique triad of hemolytic anemia, pancytopenia, and thrombosis, an indicator of paroxysmal nocturnal hemoglobinuria (PNH). Which of the following is not associated with PNH?
overexpression of protectin CD59
Which of the following facilitates the motility of Listeria monocytogenes?
polymerization of host actin
When C3 is first released into the blood, the thioester bond is
sequestered within the hydrophobic interior of the protein
Defensins are characterized as ___________.
small antimicrobial peptides
Defensins are not ____________________.
synthesized as active peptides