AAMC 7 biololology

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Normally, immune system avoids attacking tissue of own body because:

A. A special intracellular process recognizes only foreign antigens
B. the body does not make any antigens that the immune system could recognize
C. it changes its antibodies to be specific only to foreign antigens
D. it suppresses cells specific to the body's own antigens

Answer is D.

A is wrong because it is an extracellular process with the MHC's.

B is wrong because that is not how t killers work. they check out antigens of cells they come in contact with.

Why is C wrong?

Originally Posted by chiddler

Normally, immune system avoids attacking tissue of own body because:

A. A special intracellular process recognizes only foreign antigens
B. the body does not make any antigens that the immune system could recognize
C. it changes its antibodies to be specific only to foreign antigens
D. it suppresses cells specific to the body's own antigens

Answer is D.

A is wrong because it is an extracellular process with the MHC's.

B is wrong because that is not how t killers work. they check out antigens of cells they come in contact with.

Why is C wrong?

The antibodies don't get "changed" to be specific for anything. Antibodies are pre-made specifically for an antigne You are born with certain antibodies, and you get other antibodies from things like vaccinations.

Originally Posted by MedPR

The antibodies don't get "changed" to be specific for anything. Antibodies are pre-made specifically for an antigne You are born with certain antibodies, and you get other antibodies from things like vaccinations.

that's right! a bunch of different types are made randomly, and are activated by t-helpers that present the appropriate antigen + activating proteins, yes?

Originally Posted by chiddler

that's right! a bunch of different types are made randomly, and are activated by t-helpers that present the appropriate antigen + activating proteins, yes?

Yup. Each successive exposure to an antigen results in a more specific antibody.

Originally Posted by MedPR

Yup. Each successive exposure to an antigen results in a more specific antibody.

how, if we are only given a single random set? shouldn't the first exposure result in a specific antibody?

Originally Posted by chiddler

how, if we are only given a single random set? shouldn't the first exposure result in a specific antibody?

It's called affinity maturation, but I don't know very much about it. It has something to do with mutations and therefore slightly different variable regions. Proliferation (clonal selection) results in lots of antibodies, some with greater antigen-affinity than others. Only the ones with greatest affinity "survive" and therefore continue to proliferate. Thus, more exposure = more specific (greater affinity) antibodies.