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* q.2___________?
  sarim - 08/30/13 13:28
  MBME 3 Q.

MRL- lpr/lpl mice are useful in biomedical research cos they are susceptible to autoimmune diseases. These mice are characterized by a defect in fas gene and marked increase in T lymphocyte accumulation when compared to wild-type animals. Based on these findings which of the following could be the cause of increased susceptibility of these mutants to autoimmune diseases ?

A-Decreased cell cycle transit time in activated of the T lymphocytes.
B-Decreased dependence for Antigen Presenting cells for T lymphocyte activation
C-Dec responsiveness to clonal deletion signals in the thymic cortex.
D-Increased responsiveness of the mature T lymphocyted to Antigenic stimulation
E-Increased thymocyte precursor proliferation in the bone marrow.
F-Increased thymocyte proliferation rate in thymic cortex.
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* Re:q.2___________?
  psychmledr - 08/30/13 13:36

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* Re:q.2___________?
  shriti - 08/30/13 13:39
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* Re:q.2___________?
  my250 - 08/30/13 13:44

Mutation of the FAS protein prevents apoptosis of auto-reactive lymphocytes..clonal deletion of activated T lymphocytes is impaired ,therby disposing the individual to develop autoimmune dis.
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* Re:q.2___________?
  psychmledr - 08/30/13 13:48
  Thank you :)  
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* Re:q.2___________?
  sarim - 08/30/13 13:52
  "C" is correct as explained .thanks

In "Clonal deletion"(in thymus), apoptosis of auto reactive lymphocytes is done via
"Fas-Ligand and Fas-receptor - Caspases" mechanism

-plz refer "Autoimmune Lymphoproliferative Syndrome" (Canal Smith Syndrome)
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