The Expression of GAD in Beta Cells of NOD Mice is Required for the Development of Diabetes

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The Expression of GAD in Beta Cells of NOD Mice
is Required for the Development of Diabetes

• Susannah A. Hill

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Background

• Diabetes is an autoimmune disease
• Diabetes my be prevented by suppressing an
  autoimmune response

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Control of Autoimmune Diabetes in NOD Mice by GAD
Expression or Suppression in Beta Cells

• Yoon et al. 1999

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Glutamic Acid DecarboxylaseGAD is a protein
produced by beta islet cells
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A Six Part Study

• The expression of GAD is required to develop
  diabetes
• The suppression of GAD is specific
• GADs action is specific to the beta cell
• GAD acts via diabetogenic T cells
• Other B cell autoantigen-specific T cells are
  dependant upon GAD
• GAD suppressed/expressing B cell grafts

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The expression of antisense GAD was quantitated
with a Southern blot
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Histological examination of islets in high,
medium, low, and transgene-negative islets
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Conclusion

• These data are indicative of a GAD-dependant
  response

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The expression of GAD is required to develop
diabetes

• Highly anti-GAD transgenic NOD mice did not
  develop diabetes
• Moderate and low amounts of transgene prevented
  diabetes by 33 and 25 respectively
• Conclusion Beta cell GAD expression is required
  for the development of diabetes

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The incidence of diabetes at various ages is shown
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The suppression of GAD is specific

• Transgenic mice infected with a viral DNA
  developed diabetes
• Transgene-negative mice infected with viral DNA
  also developed diabetes
• Conclusion The prevention of diabetes in
  transgenic mice is not due to the nonspecific
  effect of an antisense transgene

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GADs action is specific to the beta cell

• Diabetogenic T cells were able to infiltrate into
  the salivary gland of highly transgenic mice
• Conclusion Autoimmunity is specific to beta cells

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The difference between islet cells of transgenic
(GAD) and transgene-negative lines
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The salivary gland cells in both transgenic and
transgene-negative mouse lines
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GAD acts via diabetogenic T cells

• 0 of mice receiving splenocytes from highly
  transgenic mice developed diabetes
• 90 of mice receiving splenocytes from transgene-
  negative mice developed diabetes
• Conclusion GAD expression is required for the
  generation of diabetogenic T cells

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Other beta cell autoantigen-specific T cells are
dependant upon GAD

• Immunization of NOD mice with GAD suppresses T
  cell responses to GAD, heat shock protein 60,
  carboxypeptidase H, and peripherin
• Conclusion The suppression of GAD prevents
  immune responses of other auto- antigens as well
  as GAD

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The splenic T cell proliferative response to
other islet auto-antigens
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The resilience of GAD-suppressed beta cells to
attack by grafted diabetogenic T cells

• 0 of mice receiving GAD-suppressed islets
  developed diabetes
• 100 of recipients of GAD-expressing islets
  developed diabetes
• Transplanting env-(an antisense proviral DNA),
  caused islet destruction

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The effect of GAD suppressed and expressing islet
grafts on blood glucose levels in NOD recipients
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Antisense vs. Tg- cells
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Conclusions

• The expression of GAD is required to develop type
  1 diabetes in the NOD mouse
• The resistance of GAD suppressed islets is a
  specific effect
• GAD expression is neccessary for the induction of
  diabetogenic T cells
• These CD4 and CD8 T cells cannot act without GAD