Question

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.

Answer 1

Answer: there can be two possibilities and both may work hand in hand- B.The patient's own immune system would destroy the transfused T cells before they could respond to the viral infection and

D.Donor T cell viral antigen recognition is restricted by MHC molecules not expressed in the patient.

Explanation: MHC class II are expressed on B and T cells and they will be responsible for presenting the viral peptide to T cells who will then recognize and initiate the reactions to remove viral cells.An effective immune response against viral infections depends on the activation of cytotoxic T cells that can clear infection by killing virus-infected cells. Proper activation of these T cells depends on professional antigen-presenting cells, such as dendritic cells (DCs)

Perforin first makes a pore, or hole, in the membrane of the infected cell. Cytotoxins go directly inside the cell through this pore, destroying it and any viruses inside. This is why Killer T-cells are also called Cytotoxic T-cells. The pieces of destroyed cells and viruses are then cleaned up by macrophages.