Individuals That Lack All T Cells Have the Most Severe

Multiple Choice

Individuals that lack all T cells have the most severe form of immunodeficiency (SCID) and will not survive past their first birthday without a bone marrow transplant from a healthy donor. These individuals fail to make antibody responses to the normal childhood vaccines because:

A) They generally lack all B cells
B) SCID causes a defect in B-cell receptor signaling
C) SCID patients lack AID, so their B cells cannot undergo class switching
D) Most antibody responses require T cell help for the B cells
E) Persistent infections in SCID infants disrupts hematopoiesis