Question XVIII. Patient P was diagnosed with chronic myelogenous leukemia. His e

Question

Question XVIII. Patient P was diagnosed with chronic myelogenous leukemia. His elder brother Bob (65 years old) is HLA-haploidentical and will donate bone marrow. Patient P’s oncologist has recommended him to a medical center that favors using bone marrow depleted of mature T cells prior to infusion. The rationale for employing the practice of T- cell depletion here could be [complete the sentence and (based on your immunology knowledge) assess the resulting statements (149-153) as either factually correct

(= “true”) or incorrect (= “false”)]:
149. that mature T-cell chimerism is required to establish long-term tolerance.
150. because Bob is HLA-haploidentical and male, there is no risk of alloreactivity toward major or minor histocompatibility antigens.
151. because of Bob’s age, the expected bone marrow harvest is already marginal for successful engraftment, and the absence of T-cell depletion could compromise the yield of stem cells.
152. that T-cell depletion will remove alloreactive T cells from the donor and prevent the potential for graft-versus-host disease.
153. that the risk of using a cocktail of immunosuppressive drugs outweighs the risk of contaminating the bone marrow during T-cell depletion.

Explanation / Answer

T-cells are the basis for graft rejection, since they are the cells that recognize antigens with HLA context. If T cells are removed, transplant will not induce any graft-versus-host rejection. During development and maturation of T cells, some alloreactive T cells clones are always present in the system. Since thymus cannot present all the potential antigens of the body, to developing T cells, alloreactive T cells are not completely eliminated, Instead, they are made tolerant by peripheral tolerance mechanisms.

149. False

150. False. Alloreactive cell clones are due to the fact that T cells cannot present all the allogenic antige-MHC complexes to the developing cells

151. False

152. True

153. True

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