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FA 2012 Pg. 227

Discussion in 'Step I' started by kaleerkalut, Apr 24, 2012.

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  1. kaleerkalut

    kaleerkalut

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    I had a question about the antibody structure shown. On the right half of the "Y" it shows some subunits called "Jh", "D", and "Jl". Anybody know what these are or what they do? Totally unexplained and was newly added to this edition. Thanks in advance :)
  2. JRjcu08

    JRjcu08

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    These are the segments of the variable portions of heavy and light chains that rearrange to form the BCR/TCR (BCR in this case) so that each BCR recognizes one specific Ag.
    Heavy chains rearrange first (Jh and D; light chain has no D, so they are simplifying by just writing D), then they combine with a V and a constant region. (Then transcribed to RNA...translated to protein...etc. Also Tdt nucleotides can be added during rearrangement for even more Ab diversity).
    Next, light chains rearrange (Jl only, no D) with a V and a constant region. Then the rearranged heavy chains recombine with the rearranged light chains to generate Ab diversity.
  3. kaleerkalut

    kaleerkalut

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    Thank you so much! Yeah it totally made no sense until I read your post and it clicked that this was VDJ recombination. :thumbup:

    On a different question or note:

    The last line of Graft-Versus-Host-Disease says: "potentially beneficial in bone marrow transplant". Why is this? Thanks again.
  4. JRjcu08

    JRjcu08

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    I think that "a little" GVHD is beneficial in a case of leukemia or another blood cancer, since the recipient of the BMT will have been irradiated before the transplant so they have no immune system. GVHD happens when there are still some competent CD8+ T cells from the donor, and if there are any remaining cells in the host, the donor T cells can attack and kill them.
    I think they should have specified that *mild* GVHD could be beneficial, because severe GVHD is definitely a serious complication after BMT because the donor is basically destroying the host who can't fight back.
  5. kaleerkalut

    kaleerkalut

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    Makes sense. Thanks again.
  6. JRjcu08

    JRjcu08

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    You're welcome! :)

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