All-Trans Retinoic Acid (TRA) Is a Metabolite Generated from Vitamin

question 16

Multiple Choice

All-trans retinoic acid (tRA) is a metabolite generated from vitamin A in the diet, and is a key component in generating an appropriate balance of FoxP3+ regulatory CD4 T cells versus T_H17 effector CD4 T cells in mucosal tissues. Patients with some autoimmune diseases, such as psoriasis, derive benefit from oral synthetic retinoid treatment for their condition. This indicates:

• A) A possible role for genetic defects in retinol dehydrogenase, an enzyme required to covert vitamin A into tRA, in autoimmunity
• B) That T_H17 cells play a role in all autoimmune diseases
• C) That tRA likely has systemic actions unrelated to the immune system
• D) That environmental factors such as diet can impact the onset of autoimmunity
• E) A likely role for tRNA in the development of effector CD4 T cells in the skin