Which of the following is NOT an example of a checkpoint in lymphocyte maturation that contributes to the selective maturation of cells with useful antigen receptors?
A)B cell precursors that cannot express Ig g heavy chains die by apoptosis.
B)T cell precursors that cannot express TCR b chains die by apoptosis.
C)Immature B cells that bind to self antigen with high affinity die by apoptosis.
D)Developing T cells that fail to express TCR a chains die by apoptosis.
E)Developing T cells that recognize self major histocompatibility complex (MHC)molecules with high affinity die by apoptosis.

Question

Quizplus · Accepted Answer

B cell precursors must express Ig F1F1F1S1F1F1F10 heavy chains (not Ig F1F1F1S1F1F1F10 heavy chains)to survive.The F1F1F1S1F1F1F10 chains associate with surrogate light chains in pre-B cells,which allows for the generation of survival signals.Otherwise,the cells die by a default apoptotic pathway.A similar checkpoint exists in T cell precursors,which must express TCR F1F1F1S1F1F1F10 chains that associate with pre-TF1F1F1S1F1F1F10 chains to avoid apoptotic death.Developing T cells must progress to express TCR F1F1F1S1F1F1F10 chains and form F1F1F1S1F1F1F10 TCRs to be positively selected and continue to survive.Both immature B cells and developing T cells will undergo apoptosis if they express high-affinity receptors that bind to self antigens.In the case of developing T cells,high-affinity binding to self MHC will lead to apoptotic death.

Which of the Following Is NOT an Example of a Checkpoint