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48 Cards in this Set

  • Front
  • Back
What are the INNATE immune responses to infectious diseases?
-Complement system
What are the SPECIFIC responses to infectious diseases?
Cell-mediated response (CTL)
Humoral response
Why do viruses present a unique challenge to the immune sytem?
They are intracellular pathogens and must be combated with cell-mediated immunity; humoral response is insufficient.

To inhibit the pathogen, the host cell must be affected as well.
What is a retrovirus?

An example:
A virus which inserts its dna into the host's genome.

What are the 3 main purpose of the Humoral response to infecton:
1. Defend AGAINST infection
2. Prevent SPREAD of infection
3. Neutralize viral infection by ADCC
How des IgA defend against infection?
It is secreted to the mucosal membranes and prevents pathogens from binding to host cells.

PREVENTS infection or reinfection
An action done by IgA, IgG and IgM:
prevention of viral fusion with the host cell membrane - the pathogen got through the mucosal membrane, but is prevented from inserting DNA into genome.
How do IgG and IgM function in the humoral response to infection?
Both act as opsonins by binding FcR on phagocytic cells. Allosws CLEARING of infection
What is a function of IgM alone in the humoral response:
Agglutinates viral particles - a macroprocedure, but effective nonetheless.
How is complement activated by the humoral response to infection?
When IgM and IgG opsonize, their Fc regions have C3b receptor; C3b can bind the complex and induce MAC construction and lysis.
What are the 3 components of the cell-mediated response to infection
IFN-y secretion
Cytotoxic T lymphocytes (CTLs)
NK cells
What do the three components do?
IFN-y is secreted by T cells; has antiviral activity.

CTLs kill virus-infected cells.

NK cells and macrophages kill virus-inf. cells via ADCC while Cell-med. response is being mustered.
If you're told to describe the INNATE RESPONSE TO VIRAL INFECTION:
IFN-y induces direct antiviral activity;

IFN-a and B stop viral dna replication and protein production.

NK cells are the first-line defense; kill virus-infected cells by ADCC.
Which set of cytokines is important in a viral infection?
Type I interferons
What are the functions of IFN a/b
-inhibit viral dna replication and protein synthesis

-activate NK cell activity
What are the 4 basic ways viruses can evade their host's defense system?
1. Block Antigen presentation
2. Block the complement pathway
3. Block recognition
4. Block host defense
How does a virus block antigen presentation?
By inhibiting the TAP molecule so that degraded virus cannot be presented on the surface of the infected cell as antigen.
How does a virus block the complement pathway of its host to evade the host's defense
1. Bind c4b to prevent opsonization of viruses; prevents MAC lysis.

2. Alter the protealysis pathway
How does a virus block recognition of itself to evade the host defense system?

What is the purpose?
This is a DISGUISE, by two mechanisms:

-Antigen drift
-Antigen shift
What are the characteristics of
-A drastic change in the virus subtype;
-Results from genetic recombination between different species to produce a new subtype of the virus.

-Causes a pandemic
What are the two molecules on the surface of the flu virus?
-Neuraminidase (facilitates budding)

-Hemagglutinin (attaches host to cells)
How is the genetic material stored in the flu virus?
in 8 strands of RNA.

possible to reassort.
What causes antigen drift, what is the result?
Caused by point mutations that occur all the time; results in surface molecules slihtly different, but can still cross-react so there is some protection.

LOCAL epidemic
What are 6 ways viruses can directly BLOCK the host immune system defense?
1. Infect lymphocytes/macrophages
2. Inhibit cytokine functions (mimic or block receptors)
3. Cause cytokine imbalances (suppress cytokine production)
4. Kill T and B cells
5. Be a retrovirus
6. Downregulate MHC expression
What does polychromatic mean?
There are 8 seperate strands of RNA within the flu virus; these can recombine with other virus rna
Why does Antigen drift occur?
RNA polymerase is not high-fidelity, so many mistakes occur in the replication process.
How does the immune system respond to bacteria?
If Extracellular: produces humoral antibody.

If Intracellular: Delayed Type Hypersensitivity DTH
Why does a DTH develop in response to intracellular bacteria?
Because this response is cell-mediated, and these bacteria are only presented on MHC and induce a cell-mediated response.
what is a protease inhibitor?
A drug useful for combating viral infection that inhibits reverse transcriptase and viral gene replication
what is the target of the AIDS virus?
the Thelper cell
How does the AIDS virus recognize Thelper cells?
It recognizes CD4 and serpentine chemokine receptors; after entering the cell it becomes a


and lives for a while.
Cell receptors necessary for AIDS to enter cell; which cells?
Monocytes; must have CD4 and Chemokine receptors.
5 ways Antibodies combat extracellular bacterial infections:
1. Bind/neutralize toxin produced..
2. Lysis of bacteria by activating complement (alternative pathway).
3. Ab/C3b bind bacterial surface; opsonins for phagocytosis.
4. C3a anaphylatoxin causes inflammation.
5. Chemotaxis for WBC response
Immune responses to bacteria can be pathogenic, rather than the bug itself; what are some examples?
Endotoxin causes septic shock

Exotoxin functions as superantigen, resulting in huge cytokine production.

M. tuberculosis - pathogens living intracellularly cause DTH, chronic antigenic activation of Thelper cells.
2 types of intracellular pathogens and the immune response:

Leprosy, Tuberculosis


DRUGS, taken for a loooong time.
What happens in an infection of tuberculosis?
Bacteria lives intracellularly in macrophages.
Chronic Ag presentation to CD4 tcells.

EFFECT of activated Tcells -> CTLs release lytic granules to kill targets.

Chemotaxis for activated macrophages causes granuloma -> TUBERCLE walls off bug.
4 ways that bacteria invade the host:
1. Attach to host cells
2. Proliferate
3. Invade host tissues
4. cause damage with toxins
4 ways hosts defend against bacteria:
1. block attachment to host cells with IgA
2. prevent prolif by opsonizing for phagocytosis; or by MAC-lysis and inflammation.
3. Use Ab-mediated agglutination to prevent invasion of tissues
4. Neutralize toxins with antibody
6 mechanisms by which bacteria evade the host defense against the bacteria:
Secrete proteases to cleave IgA
Vary Antigenic structure
3. Inhibit phagocytic cells
4. Resist MAC insertion (Gram pos)
5. Membrane molecules to resist MAC insertion (GRAM neg)
6. Secrete molecules to inactivae C3a/b
Life cycle of Protozoa
1. Blood meal; sporozites enter blood.
2. To liver; multiply, transform liver cells, release many babies.
3. babies infect RBC, rupture, release more babies.
4. Get ingested by another mosquito eating; differentiate, transmitted agian.
What causes malaria?
plasmodium, a protozoan
4 Challenges of Plasmodium:
1. Many phases in life cycle make specific immune response difficult.
2. Many babies - MUCH Ag;
3. Sporozoites only circulate 30 min before going to liver.
4. Sporozoites antigenic phenotype changes alot
Solutions for Malaria:
develop a vaccine
develop new drugs to replace old resistant ones
best stage of plasmodium life cycle to administer a vaccine:
the sporozoite stage (before going to the liver and having babies)

not useful tho, becuase this is only 30 minutes and immune response takes longer
what is Schistosomiasis?

How is it transmitted
disease caused by Schistosome - a parasitic worm.

Contact with swimming larvae
Process of Schistosomiasis:
1. Larvae bore between toes
2. enter capillaries/blood Travel to Mesenteric veins or the bladder.
3. Mature into adult worms.
4. Have eggs; get into feces and urine.
5. Spread eggs.
Where would be the best vaccine to schistosomiasis?
Early in the stage of infection, maybe the larvae or adult worms but before generation of eggs.
What are the challenges presented by schistosomiasis?
1. only one worm, hard to stimulate immune response.
2. only one worm; hard to find it to neutralize.
3. Motile worm; evades immune response that is generated.
4. worm expresses ABO antigens; not recognized as foreign