Question

True or False

A]  In the case of Central Tolerance for T-cells, it takes place in the thymus, specifically, positive selection takes place in the cortex and negative selection takes place in the medulla.

B] The AIRE gene codes for information allowing for the expression of self-antigens by epithelial cells in the thymus cortex allowing for immature T-cells to be “educated” about self-components.

C] An important concept of Central Tolerance that explains how B-cells develop tolerance is receptor editing. This concept basically states that B-cells have more than one opportunity to select V-genes that encode for the antigen binding site. If they select an idiotype that binds self they get second or third chance to select different light chain V-genes.

D] In Peripheral Tolerance professional antigen presenting cells (APC) and T-regulator cells influence T-helper cells to only respond to non-self and not to self-antigens.

E] Secondary immunodeficiency diseases can result from exposure to environmental factors, drugs, or aging.

Answer 1

A) True - T cell central tolerance - Positive selction in cortex and negative selction in medulla.

B) False - Transcription factor autoimmune regulator (AIRE) - expressed in thymus medulla not in cortex - and eliminates self reactive T cells.

C) True - In B cell both light and heavy chain V regions can be replaced during receptor editing.

D) True - primary function of T cells is to prevent autoimmune disease. Both APC ( by releasing cytokines) and T cells regulate Th cell activities

E) True - Secondary immunodeficiency diseases can result from exposure to environmental factors, drugs, or aging.