A Child Who Suffers from a Persistent Viral Infection Is

A child who suffers from a persistent viral infection is found to have a deficiency in lymphocyte production and very few T and B cells.Other bone marrow-derived cells are produced in normal numbers,and MHC molecule expression on cells appears normal.Transfusion of mature T cells from an unrelated donor who had recovered from a previous infection by the same virus would not be expected to help the child clear his infection.Which one of the following is a reasonable explanation for why this therapeutic approach would fail?

A) Viral infections are cleared by antibodies,not T cells.
B) The patient's own immune system would destroy the transfused T cells before they could respond to the viral infection.
C) T cells recognize peptides,not viral particles.
D) Donor T cell viral antigen recognition is restricted by MHC molecules not expressed in the patient.
E) In responding to the previous infection,the donor would have used up all his T cells specific for that virus.