Re:nbme form 11 block 1 q 17 confusion???????? - phagocyte

[ArchivalUser]

http://www.lsic.ucla.edu/classes/mimg/te...weirtz.pdf



may be helpful

ans.. b or e

[ArchivalUser]

i also did it...plz write a question

[ArchivalUser]

During experiment the us11 gene product of cytomegalovirus is expressed constitutively after stable transfection in an experiment tumoer cell line.it is found that this gene product causes translocation of nascent class 1 mhc molecules from the endoplasmic reticulum into cytosol.which of the following is most likely to occur regarding the class 1 mhc product??


a . association with invariant chain

b.binding of peptide from the endocytic pathway

c.degradation by the proteasome

d.formaton of class1mhc/mhc2 mhc hybrid molecules

e.interaction with the T lymphocyte receptor

[ArchivalUser]

i think ans is C-....its CMV protection mechanism,in which downreg.MHC-I expression,preventig getting to the surface...in the cytosole these substance are degrad.b/c they have lost theire own function

[ArchivalUser]

answer by maryam2009 - 05/27/11 14:19

*************************correction for Q10**********************



The answer is 4..As i already explained earlier that plasmid transfer between bacterias needs cell to cell contact through conjugation.And E coli is notorious for that.

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?

[ArchivalUser]

sorry wrong post .............

[ArchivalUser]

#2403184
maryam2009 - 05/27/11 15:22

correction...

Q17.CC

CMV has a unique method of escaping immune response it dec. the expression of MHC 1 and also expresses a decoy molecule. The normal for the MHC 1 molecule is that its made in the RER and then transported to the Cell membrane. If it get translocated to the cytosol, its likely to be degraded.

[ArchivalUser]

Yes, C 100%

If you want to be sure, find this article

The Human Cytomegalovirus US11 Gene Product
Dislocates MHC Class I Heavy Chains from the Endoplasmic Reticulum to the Cytosol

[ArchivalUser]

for a second disregard the Cytomegali virus...... and think of the concept... mhc1 and mhc2

mhc 1 is associated with cytotoxic t cells = associated with endogenous viral infections
mhc 2 is associated with t helper cells [th1 and th2] = associated with exogenous bacterial infection

mhc 1 is found within the ER and encounters virus in small pieces [viral peptides or self peptide] within the cytoplasm after virus is broken down via TAP and then sent to CM for recognition

mhc 2 is within the cytoplasm from the beginning and gets its invariant chain degraded via the ↓ in PH than attaches to the bacteria and gets sent to Cell membrane for recognition

if the virus causes a translocation from the ER to cytosol that would mean that the MHC 1 molecule can't function normally like its suppose to and recognize endogenous viral proteins thus acting like a MHC 2 molecule.... but u see this molecule does not have a invariant chain therefore i assume it would attach to the bacteria without any effect from the PH so i would say either it forms a MHC HYBRID molecule [d] or be degraded by PROTEASOMES [c] and IN SUCH SCENARIO NATURAL KILLER CELLS WOULD TAKE OVER THE ACTION Where u have the absent of MHC 1 molecule.........

[ArchivalUser]

please correct me if im wrong in my concept....