drk1980
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After a full course of immunization with a new vaccine consisting of a recombinant polypeptide. 10% of adults fail to make antibody to the polypeptide. The nonresponders have an increased frequency of one HLA type. What is the most likely explanation for the failure of this group to respond to immunization?
A. B cell can't recognize this peptide
B. T cell can't recognize this peptide
C. Lack of class I MHC presentation of this peptide
D. Lack of class II MHC presentation of this peptide
Edited by drk1980 on 01/30/06 - 09:59 AM
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| sturge_weber
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D , i think
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| reet
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yes,, D
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| doc179
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D?
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| sarika
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plz explain
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| skyhigh
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yes, why d?
doesn't presence of HLA mean that MHCII is also present
Shouldn't it be A, failure of B cells to recognize peptide?
Edited by skyhigh on 01/29/06 - 06:57 PM
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| doc179
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its the bare lymphocyte syndrome in which the MHC2 is mutated. in the question note that there is increased frequency of one HLA type that means its either MHC1 or MHC2 . if it was MHC2 then there could have been no deficiency of any of the antibodies.
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| sturge_weber
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there re two types of hla, hla abc and hla dp dq dr... all these re formed by the mhc classes... i mean mhc 1 forms the hla a b c and so on. now in this question he says that one type of ab not being made, and one type of hla is increased, that means ... some problem with the mhc, and hence i think the answer
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| doc179
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I was also actually thinking abt the same thing ...but I have not come across such a thing that there is this particular defect in T or Bcell to recognise a peptide where the MHC molecules are doing their work properly..I might be wrong ..but I have not studied such a defect...but I do have studied the bare lymphocyte synd. and the genes A,B and C of MHC1 and DR,DP, and DQ of MHC2 are expressed codominantly so if a particular combination of them in a particular MHC2 is expressed after a mutation then I think it will not be able to present antigens to CD4...correct me if I am wrong
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| doc179
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drk1980 ...is my ans correct?
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| drk1980
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i just found this! i think this stem is closer to the real NBME Q...Sorry abt the earlier one, kinda incomplete!
After a full course of immunization with a new vaccine consisting of a recombinant polypeptide. 10% of adults fail to make antibody to the polypeptide. The nonresponders have an increased frequency of one HLA type. What is the most likely explanation for the failure of this group to respond to immunization?
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| sturge_weber
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ya thats how it was in the test
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| drk1980
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doc179, these are NBME Qs. Only NBME can answer your doubt......and ofcourse maybe some wise soul here on these forums 
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| doc179
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does not NBME has the answers for the questions in it?
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| drk1980
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No, unfortunately NBME does not release the answers to their Qs. Their Qs are for the sole purpose of judging your readiness for the USMLE. The NBME Qs are the closest to the real exam Qs in terms of difficulty level.....and quite a few are even repeated on the USMLE....so its worth discussing them. u may want to chk out nbme.org for more info.
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| doc179
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thank you very much..and sorry abt the trouble
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| drk1980
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no trouble at all buddy! not any more than the big one..... 'USMLE' 
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