Immunological responses in identical twins with renal transplants from a common donor.

Two identical twins suffering from end stage renal failure due to chronic pyelonephritis received cadaver renal allografts from one donor. Immune status was measured in both by in vitro responses to vegetable mitogens and by reactivity in mixed lymphocyte culture with a random volunteer. Both patients underwent rejection episodes at different times; these were of differing severity. Reactivity to PHA and in MLC was minimal during rejection and increased following recovery in spite of continued high levels of immunosuppression. In contrast, reactivity to pokeweed mitogen and concanavalin A increased at the time of rejection and fell with recovery. The changes seen in the twins, while qualitatively similar, differed in magnitude and timing. It is concluded that environmental factors as well as histocompatibility play a part in influencing immune responsiveness, and that studies of immune responsiveness should be interpreted with caution in the management of renal allograft recipients.