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NBME 24 Answers

nbme24/Block 2/Question#45

A 2-year-old boy is brought to the physician ...

Peptide transporter (TAP)

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 +11  upvote downvote
submitted by lsmarshall(267),

MHC class 1 peptide antigen processing > "Antigen peptides loaded onto MHC I in RER after delivery via TAP (transporter associated with antigen processing)" - First Aid 2019.

Bare lymphocyte syndrome type 2 (BLS II; affecting MHC II) is due to mutations in genes that code for transcription factors that normally regulate the expression (gene transcription) of the MHC II genes. Bare lymphocyte syndrome type 1 (BLS I; affecting MHC I), is much more rare, and is associated with TAP deficiencies.

ADA mutation = autosomal recessive SCID

IL-2-R gamma chain mutation = XLR SCID

IL-2-R alpha chain (CD25) = T-reg dysfunction; assoc with autoimmunity esp. T1DM, MS

Fas ligand (CD95) mutation = no T cell apoptosis in negative selection in thymic medulla = incr circulation of self-reacting lymphocyte = autoimmune lymphoproliferative syndrome

 -2  upvote downvote
submitted by yotsubato(520),

Cool another question taken from the list of things not in FA

charcot_bouchard  Actually it is in FA. FA 19 Page 100 - Antigen loaded onto MHC1 in RER after delivery via TAP transporter.... Remember FA is that friend who always say I told you so. +4  
yotsubato  But not in this context +1