BIOL 221 Lecture Notes - Lecture 6: Complement Membrane Attack Complex, Opsonin, Lysis

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1 Mar 2020

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Complement Activation

•Classical pathway

–Activation by interaction with antigen-antibody complex

•Alternative pathway

–Complement protein stabilized by interaction with antigens

● The classical pathway starts when a specific complement protein

interact with antigen-antibody complex(McGraw-Hill Education, 2017);

this is an example of the interaction between adaptive and innate

resistance.

● The alternative pathway occurs as antigens interact directly with a

different complement protein resulting in activation of complement

proteins.

Activated Complement

•Lyse cells by insertion of MAC (membrane attack complex)

•Enhance inflammation

•Neutralize viruses

•Stimulate chemotaxis

•Enhance phagocytosis

–opsonization

● Activated complement proteins lyse cells by insertion of complement

proteins (called the membrane attack complex or MAC) into the plasma

membrane of the cell; enhance inflammation; neutralize viruses;

stimulate chemotaxis (drawing leukocytes to the area), and enhance

phagocytosis by opsonization.

Chemical Defenses: Interferons

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Document Summary

Activation by interaction with antigen-antibody complex: alternative pathway. The classical pathway starts when a specific complement protein interact with antigen-antibody complex(mcgraw-hill education, 2017); this is an example of the interaction between adaptive and innate resistance. The alternative pathway occurs as antigens interact directly with a different complement protein resulting in activation of complement proteins. Activated complement: lyse cells by insertion of mac (membrane attack complex, enhance inflammation, neutralize viruses, stimulate chemotaxis, enhance phagocytosis. Chemical defenses: interferons: proteins secreted by somatic cells infected with virus, activated lymphocytes and macrophages, virus. Nonliving pathogen: protein capsid, nucleic acid (dna or rna [retroviruses]) Use host cells" materials and processes to replicate. Interferons are proteins secreted by somatic (body) cells infected with viruses and by activated lymphocytes and macrophages. Viruses are nonliving pathogens consisting of a protein capsid surrounding a nucleic acid (either dna or rna, the latter in retroviruses). Viruses use the host cell"s materials and processes to replicate.

Related Questions

Which of the following is a characteristic of the adaptive immune system?

a .It is a specific response against microbial antigen

b. It includes inflammation.

c. It activates the alternative complement pathway.

d. It includes defenses on the body surfaces.

2. C-reactive protein is an opsonin because it:

a. creates a channel in bacterial membranes

b. increases C3b binding to a microbe.

c. forms the pathogen-associated molecular patterns.

d. enhances phagocytosis.

3. The rapid increase in antibody production after repeated exposures to the same antigen is due to:

a. antibody-dependent cellular cytotoxicity.

b. higher levels of IgE

c. presence of memory cells.

d. clonal proliferation of NK cells

4. Cytotoxic T cells can kill cancer cells by:

a. inducing apoptosis with granzyme.b. release of membrane attack complex.

c. activate the production of complement C3b

d. phagocytosis of opsonized cells.

5. Which event is not required for the activation of helper T cells?

a. The presence of interleukin-1

b. Binding of CD8 receptors

c. Binding of matching non-antigenic proteins of the antigen-presenting cel

d. Presentation of an antigen bound to class II MHC

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1.How do some pathogens prevent complement activation or avoid the effects of activated complement?

A. some pathogens hijack the host's regulatory membrane proteins that inactivate C3b, preventing the triggering of the alternative activation pathway AND some pathogens produce C5a peptidase that causes destruction of phagoctyes recruited to the area of infection

B. some pathogens produce C5a peptidase that causes destruction of phagoctyes recruited to the area of infection

C. some pathogens produce C5a peptidase that destroys complement C5a, a chemoattractant that recruits phagocytes to the area of infection

D. Some pathogen hijack the host's regultory membrane proteins that inactivate C3b, preventing the triggering of the alternative activation pathway AND some pathogens produce C5a peptidase that destroys complement C5a, a chemoattractant that recruits phagocytes to the area of infection.

2. One of the most important jobs of dendritic cells is

A. production of complement proteins

B. activation of T cells by breakdown of whole antigens and presentation of antigenic epitopes on MHC molecules

C. stimulation of cytokine production by neutrophils

D. activation of B cells by combining epitopes and presentation of whole antigens on MHC molecules

E. production of IgD

3. Normal Microbiota

A. play no role in affecting pathogen growth

B. are the organisms that typically reside on and in your body

C. enhance infection by pathogens

D. are the organisms that typically reside on and in your body AND protect aganist infection by pathogens

E. protect against infection by pathogens.

4. why is the process of gene rearrangement used in creating antibodies and T-cell receptors (TCRs) so important?

A. the given choices are all reasons that generearrangement is critical in adaptive immunity

B. This is how our systems produce memory of previous exposures, a key trait in adaptive immune responses

C. without it, we would need a single gene for every antibody and TCR required to mount all the possible responses needed during our lives

D. interactions with antigens stimulate cells to initate these processes, building the best and strongest response possible to that antigen

E. this is the same DNA altering process that leads to cancer. Understanding it leads to better treatments for cancer.

1. Select which of the following are mechanisms used by pathogens to avoid host defenses and to successfully colonize the host.

A. Producing siderphores to obtain iron from the host for growth

B. producing adhesins for damaging host cells

C. Avoiding IgA proteases for avoiding secretory IgA

D. Avoiding secretory IgA by rapid turnover of pili

E. Producing toxic substances to suppress host responses

2. People considered obese have a different normal flora in the gastrointestinal tract compared to people who are considered lean.

A. true

B. false

3. Which of the following is NOT a mechanism used by pathogens for avoiding or surviving phagocytosis?

A. Killing macrophages and neutrophils

B. Colonizing the phagocyte

C. inhibiting opsonization

D. Inhibiting phagocte chemotaxis

E. these are all methods of avoiding or surviving phagocytosis

4.Which of the following immune responses is best suited to prevent a virus from infecting a cell?

A. complement cascade

B. inflammation

C. Virus-specific antibodies

D. Fever

E. phagocytic cells

5. Which of the following is NOT a method used by pathogens for penetrating skin or mucous membranes?

A. Injection of effector proteins that induce endocytosis

B. Exploiting antigen-sampling processes

C. these are all mechanisms for penetrating skin or mucous membranes

D. Exploiting an injury

E. Production of endotoxin

6. Antibodies, which are produced as part of the adaptive immune response, can sometimes be damaging rather than beneficial. People suffering from an autoimmune disease called antiphospholipid antibody syndrome (APS) make antibodies that bind to phospholipids. Some of the signs and symptoms affected individuals experience are blood clots, stroke, heart attack, and kidney damage. What is the likely cause of these symptoms?

A. the anti-phospholipid antibodies cuse immune complexes that lodge in the affected organs

B. The person fails to make protective antibodies

C. The anti-phospholipid antibodies weaken certain organs that contain fat

D. the person makes antibodies that bind inappropriately to bacterial capsules, preventing phagocytosis of these cells

E. Cell damage caused by binding of these antibodies initates inappropriate coagulation events which inferfere with blood flow in affected organs.

7. Only Gram-positive bacteria produce exotoxins

A. true

B. False

8. Which of the following members of the normal microbiota inhibit the growth of Candida albicans?

A. Lactobacilus species

B. Staphylococci species

C. E. coli

D. Neisseria species

E. Propionibacterium species

9. Would an antibody response against the B subunit of an A-B toxin protect against the effects of the toxin?

A. yes. if antibodies bind to the B protion, the toxin can no longer bind to target cells and will thus not affect those cells

B. No, even if antibodies bindto the B portion of the toxin, it is the A portion that actually causes damage to the cell

C. This question cannot be answer. The immune system does not mount a strong response against proteins, so this situation is unlikely to occur.

D. Yes, if antibodies bind to the B protein, that portion of the toxin does not become activated, and thus does not damage the host cell

E. No, even if antiibodies bind to the B portion of the toxin, the toxin is still taken into the host cell by phagocytosis, damaging that cell

10. Please select the correct definition of balanced pathogenicity.

A. A host-parasite relationship in which the parasite persists in the host, causing maximal harm. The pathogen becomes more virulent while the host becomes increasingly susceptible.

B. A mechanism that allows bacteria to transfer gene products directly into host cells, inducing changes such as altering the cell's cytoskeleton structure

C. A generated balance in the microbiome that may be caused by taking antimicrobial medication. it generally helps the host maintain optimal health

D. A situation in which an abnormally high number of T-helper cells are stimulated, causing a massive release of cytokines.

E. A host-parasite relationship in which the parasite persists in the host while causing minimal harm. The pathogen becomes less virulent while the host becomes less susceptible

11. Bacteria may survive phagocytosis by

A. preventing encounters with phagocytes AND preventing fusion of two pathogosomes

B. avoiding recognition and attachment of lymphocytes AND lysinf the phagosomes

C. preventing fusion of the lysosome with the phagosome AND mimicking host molecules

D. lysing the phagosome AND mimicking host molecules

E. preventing fusion of the lysosome with the phagosome AND lysing the phagosome

BIOL 221 Lecture Notes - Lecture 6: Complement Membrane Attack Complex, Opsonin, Lysis

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