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NBME 22 Answers

nbme22/Block 3/Question#5 (64.0 difficulty score)
A 72-year-old man with multiple myeloma ...
Unrearranged immunoglobulin gene🔍

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submitted by sacredazn(80),
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ehT etcocpn si a cvndoutelo yaw fo ksnagi if ouy wekn ohw VDJ nmotbiinocear skw,ro hwhic is taht it is cltuyala na mxaleep fo itleagnr the DAN of hte /BT .hcoyltmeyp

orSthenu blot ecqhtui:en So ewhn hyet eus a obpre agnsiat soem rone,gi and tuiugtpont a szie of .15 kb or 6 b,k hsit is glleint uyo het izse fo eht NAD amentgrf ni chea ecll t’osned( rtamte fi yeth sya J erpbo ro ctntosan ongeri bp,eor trhyee’ stuj nsagiy yeet’hr eagttigrn meos lteoncueid uqncesee ufodn ni the gI uRc/CsTlo btae ahcni uclso csrepeeilvty for TB/ .ecls)l

I tnhik the snuifcngo prta dcluo eb nrodgeiwn hwo uyo kown ewhther ey’uro tylapr tghouhr rnmrnaereetga rn(awes cchseoi B truh D) ro fi ti hna’ts rccordue ta lla yet (ectcorr rs).eawn e,Her teh ocepnct is ttha B cesll gdnreuo )VDJ( mrrnreeeaangt in eht nobe arrwmo, eihwl T sllec od ti in het yuth,sm dan ti all hneppas at oc.en oS a smpala llec in het dloob liek ni iepltlMu yamolMe udlow haev yullf rendeguon obrtn,onimecai lehiw a T lcle in het oolbd oculd rheeit be uylfl dedutaec (nad vaeh ehsfdini DVJ oac)obmrnietin or aerummti (h’nsat edratts )D.VJ

icSen hte T cell eneg aws 6 kb adn tfeediynli bgrige hant eht 15. kb gn,ee het T elcl shnt’a edngonuer inaentoriobmc .yet

trichotillomaniac  very nice explanation! +26  
nwinkelmann  This was awesome! Made so much sense and hopefully I will be able to think that critically about questions in the future (because I NEVER would have come up with this on my own, hah). +4  
eacv  OMG! THANK YOU. I DIDNT KNOW ANYTHING about this!! Hope this is not testesd on real examen :p +4  
ajss  wow! this explanation was awesome! thanks! +  
mrglass  Also the T-cell V-D-J segments are not the same as the B-cell V-D-J segments. Therefore a B-cell J segment southern blot would look for whether the B-cell site VDJ segment in a T-cell, which would always non-rearranged. +6  
mynamejeff  Thank you! So is this because multiple myeloma produces excessive monoclonal light chain Ig? Is this the 1.5 kb gene? Whereas, T-cells that have not gone through differentiation yet and their J region includes everything (VDJ) vs. just VJ in the light chain? (FA 2020 pg 104) +  
peridot  This explanation is amazing! However, to fully understand another step of what the question is getting at, please take a look at @highyieldboardswards's and/or @mrglass' explanation as well - a very important addition!! +  

submitted by highyieldboardswards(13),
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htSor rna:wes All sgene rea pternes ni ohbt B and T selc,l utb ethy garrrneea adn rpesxse soctreepr atht aer csfeciip ot ihtre .ielange erhiT are eenptdndeni DVJ nroigse orf B lcel rreoptec oineagrent nda T clel rerceotp neeoitgrna! shTi wiki clreait sdhse igtlh no ih:ts


I oto ctiarlyagl sedmsi tbu it si luycatal so spliem ahtt we rea nsigsim the reotsf goruhth eht tsere eh- -iWl btho B nad T esllc udogner JDV neerrag,aternm eth ,V ,D nda J esgen ear ENFERDTIF ESENG ditpees nigeb nzeiaodrg nad fhoeerrte dlicaseifs ni a imirasl oafhins eud to thrie hdsaer ndee ot enaetegr risevde scrrest.uut To amek rtsemat moer gosfic,nun bhot sest of DJV segen aer on cshmemrooo 4.1

hisT is hwy het MBNE pidceeisf hatt ehty era gtnaggi TEH EMAS J GIRNEO wihch si ttah of eht B llec poterrce eeng J i,rngeo nto het T llce ecerotrp eneg bta-eJ renigo see( ikiw iatec.)lr heT B elcl torperec eegn si otn nradgerare in a T ,ecll fi it s,aw T elcsl luwod eahv tnodisibae!

redstrat  This. So much this! +1  

submitted by david_bball(6),
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ehT wya I hgottuh aoubt hits etuosiqn was ttah in MM treeh si a TNO of aibndtoesi ngieb maed, so hte JVD stengem si eginb bkoern edterra/seenegcrp/dlua myan iesmt nda hsa been hodneesrt to 1kb.5. As ofr het T l,Csle ahtt niroeg stin’ ignbe used (sneic eetrh is on olcnal eioaxnpns or lenecs)ito os ti’s ltlis got hte full b6k genhlt uuodehtnc.

d_holles  T cells still undergo VDJ recombination to form their TCRs. +2  

submitted by sam1(16),
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heilW T lcles do esu eth VJD moict,ebnaroni eht T elcl ercoptre asinch rae rnifdfete gseen morf het B lc'lse haeyv adn igtlh .shcian ceiSn ehty dues a B clel -oJenrgi ,peorb hte T e'lslc bnda illw be chmu arlgre as tsih aear of sit AND e(th B clel yvhae or gihtl ihacn e)egsn hvea nto neeb randeeagrr -- aisentd sti T ecll oetrrcep genes have nebe