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tyrionwill
in the question, it says absence of MHC-I presenting cells. I guess the meaning is lack of MHC-I. IF TAP is missing or dysfunction (bare lym syn type-1), MHC-I should be there, however Ag cannot be loaded to the MHC-I. Can anyone help me to understand more.
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peridot
@tyrionwill From wiki: "The TAP proteins are involved in pumping degraded cytosolic peptides across the endoplasmic reticulum membrane so they can bind HLA class I. Once the peptide:HLA class I complex forms, it is transported to the membrane of the cell. However, a defect in the TAP proteins prevents pumping of peptides into the endoplasmic reticulum so no peptide:HLA class I complexes form, and therefore, no HLA class I is expressed on the membrane. Just like BLS II, the defect isn't in the MHC protein, but rather another accessory protein."
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j44n
i hate this question because MHCI is on all nucleated cells. So this person is literally a bag of RBC's
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soccerfan23
@j44n Not quite. It's true that MHC I is on all nucleated cells. Because of the TAP mutation, these cells don't express MHC I on their membranes. But these cells still exist. That is what is meant when the vignette says "flow cytometry shows absence of class I MHC-expressing cells.
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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.
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submitted by โlsmarshall(465)
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.