ImmunoQuestion

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I'm a bit confused about this question...can any of you help me answer?🙂

You are visited by an 6 yr old who has had nausea and vomiting for 12 hours accompanied by frequent episodes of watery diarrhea. Unremarkable physical exam.History reveals that other children in her class have had similar symptoms over the past week. In these cases, vomiting almost always subsided within 1 day although the diarrhea persisted for up to 4 days. Thereafter all affected children returned to good health. You determine that this probably represents a benign, community acquired enteric viral infection. The short duration of the illness in your patient's peers is explained by:

A. A rapid CD8+ cytolytic T cell responses to virus infections.

B. Development of an antibody response that neutralized infectivity of this enteric virus.

C. Production of type I interferons by infected cells and the ability of NK cells to eliminate virus infected cells.

D. Complement -mediated lysis of the viral host cells.

 

[mercaptovizadeh]

I'm a bit confused about this question...can any of you help me answer?🙂

You are visited by an 6 yr old who has had nausea and vomiting for 12 hours accompanied by frequent episodes of watery diarrhea. Unremarkable physical exam.History reveals that other children in her class have had similar symptoms over the past week. In these cases, vomiting almost always subsided within 1 day although the diarrhea persisted for up to 4 days. Thereafter all affected children returned to good health. You determine that this probably represents a benign, community acquired enteric viral infection. The short duration of the illness in your patient's peers is explained by:

A. A rapid CD8+ cytolytic T cell responses to virus infections.

B. Development of an antibody response that neutralized infectivity of this enteric virus.

C. Production of type I interferons by infected cells and the ability of NK cells to eliminate virus infected cells.

D. Complement -mediated lysis of the viral host cells.

My inclination is to say it's B.

A. Important in viral infection, but most virus is mopped up by antibody. CD8+ cells can't keep up with the vast quantities of virus.

B. Antibodies mop up extracellular virus. CD8+ "flush" them out of their hiding places by killing the cells that harbor them.

C. I think this is important in some viral infections, but not in all. NK cells act on cells not expressing MHC I, and not all viruses necessarily downregulate MHC I. Interferon is important in all viral infection.

D. Complement is most potent in that it opsonizes infective particle for phagocytosis and it also chemotactically recruits neutrophils. The MAC is a comparably minor effect (most important in Neisseria infections, as evidenced by people with deficiencies in the later C' components of the MAC).

 

[bgreet]

Doesn't it take 5-10 days to mount an initial full blown humoral response? I would be inclined to say C (innate immunity) since it's under 5 days, and NK can work on antigen specific markers via ADCC (Antigen Dependent Cell mediated Cytotoxicity)

 

[mercaptovizadeh]

Doesn't it take 5-10 days to mount an initial full blown humoral response? I would be inclined to say C (innate immunity) since it's under 5 days, and NK can work on antigen specific markers via ADCC (Antigen Dependent Cell mediated Cytotoxicity)

Actually, you're probably right. I didn't notice the timing. It would need at least 4 days to start mounting the response.

 

[SOUNDMAN]

Yea the timing is too soon for an Antibody response. Host defense for viral infections includes:

1. Initial Innate Immunity with activation of NK cells and stimulation of Interferon alpha and beta by the virus infected cells. This acts to inhibit viral replication in surrounding uninfected host cells

2. "Early viral infection" NK cells lyse virus-infected cells early before adaptive immunity

3. During "Late viral infection" ADCC is going on and NK cells lyse infected host cells

4. CD8+ CTL's are main immune response during an ESTABLISHED viral infection, because they can lyse viral infected cells, before replication has been completed. This usually occurs 1 - 2 weeks after an initial viral infection.

I would be inclined to got with "C" as well, but what exactly is a "rapid" CD8+ response...I love ambiguity.

 

[Dogg1]

I think it would be A. Remember with alot of viral illnesses, symptoms are not seen until several days after infection has happened. Thus a person is asymptomatic even though they are infected and contagious. Symptoms do not manifest until a certain viral load is reached and by that point the body has produced a cell mediated CD-8 immune response. If it was not a cell mediated response, the body would not be able to rid itself of the infection as it could always exist within cells. Or so I believe