The thymic cortex is where positive selection of T cells takes place. Positive selection is a process that tests if T cells can bind to self-MHC well enough above a certain threshold to function properly. If the binding is too weak, the T cell undergoes apoptosis.
Bcl-2 is an anti-apoptosis gene. If cells that reach the thymic cortex have a constitutively active Bcl-2 gene, they would not undergo apoptosis despite weak self-MHC binding. Thus, you would have failure of positive selection and "decreased cell death in the thymic cortex" which was the correct answer.
Also, remember that after positive selection in the thymic cortex, the T cells go on to the thymic medulla for negative selection where the cells undergo apoptosis if they bind to self-MHC too strongly (ie risk for auto-immunity)
Simple way to think about it: remember a disease that presents in the same way aka Follicular Lymphoma which has constitutively active bcl-2. aka follicular lymphoma promotes it nasty cancerous ways via decreasing cell death.
submitted by โsolidshake(25)
The thymic cortex is where positive selection of T cells takes place. Positive selection is a process that tests if T cells can bind to self-MHC well enough above a certain threshold to function properly. If the binding is too weak, the T cell undergoes apoptosis.
Bcl-2 is an anti-apoptosis gene. If cells that reach the thymic cortex have a constitutively active Bcl-2 gene, they would not undergo apoptosis despite weak self-MHC binding. Thus, you would have failure of positive selection and "decreased cell death in the thymic cortex" which was the correct answer.
Also, remember that after positive selection in the thymic cortex, the T cells go on to the thymic medulla for negative selection where the cells undergo apoptosis if they bind to self-MHC too strongly (ie risk for auto-immunity)