One question a day Q#6 RC 02032014
The transplantation of organs from one individual to another normally involves two major problems: (1) organ rejection is likely unless the transplantation antigens (a usually protein or carbohydrate substance (as a toxin or enzyme) capable of stimulating an immune response) of both individuals are nearly identical, and (2) the introduction of any unmatched transplantation antigens induces the development by the recipient of donor-specific lymphocytes that will produce violent rejection of further transplantations from that donor. However, we have found that among many strains of rats these “normal” rules of transplantation are not obeyed by liver transplants. Not only are liver transplants never rejected, but they even induce a state of donor-specific unresponsiveness in which subsequent transplants of other organs, such as skin, from that donor are accepted permanently. Our hypothesis is that (1) many strains of rats simply cannot mount a sufficiently vigorous destructive immune-response (using lymphocytes) to outstrip the liver’s relatively great capacity to protect itself from immune-response damage and that (2) the systemic unresponsiveness observed is due to concentration of the recipient’s donor-specific lymphocytes at the site of the liver transplant
Which of the following new findings about strains of rats that do not normally reject liver transplants, if true, would support the authors’ hypothesis?
I. Stomach transplants are accepted by the recipients in all cases.
II. Increasing the strength of the recipient’s immune-response reaction can induce liver-transplant rejection.
III. Organs from any other donor can be transplanted without rejection after liver transplantation.
IV. Preventing lymphocytes from being concentrated at the liver transplant produces acceptance of skin transplants.
(A) II only
(B) I and III only
(C) II and IV only
(D) I, II, and III only
(E) I, III, and IV only
No OE available
Source: GRE Big Book
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