Question

What occurs if the VDJh rearrangement is non-productive, i.e. there is a failure to express a pre-BCR? (2 opportunities to form...?)

A) Apoptosis or receptor editing
B) Proliferation or differentiation
C) Anergy or tolerance
D) Isotype switching or somatic hypermutation

Answer 1

The correct outcome for a non-productive VDJh rearrangement is apoptosis or receptor editing. These mechanisms involve the elimination or alteration of B cells to prevent autoimmunity and maintain immune system homeostasis.

Step-by-step explanation:

If VDJh rearrangement is non-productive, meaning the B cell's receptor is unable to express a functional pre-B cell receptor (pre-BCR), the B cell usually undergoes negative selection mechanisms, which are critical for preventing autoimmunity. Non-productive rearrangement can lead to two main outcomes for the developing B cell: apoptosis or receptor editing. Apoptosis is the programmed cell death that eliminates the B cell, whereas receptor editing refers to the alteration of the B cell receptor (BCR) to change its specificity.

If the rearranged receptor is self-reactive, clonal deletion can also occur through apoptosis, removing potentially harmful B cells. In some cases, non-reactive B cells may undergo clonal anergy, making them non-functional if they encounter soluble self-antigens in the bone marrow. Thus, the correct answer to the question is A) Apoptosis or receptor editing.