Infectious Tolerance

Models of transplantation tolerance induced with anti-CD4 or anti-CD40L antibodies showed that tolerant mice did not reject the grafts even after the adoptive transfer of lymphocytes from a non-tolerant animal.5,6,25 It was also demonstrated that spleen cells from animals made tolerant to skin and heart grafts using anti-CD4 or anti-CD40L antibodies could regulate naïve T cells, and in so doing, rendering them regulatory in their own right.7,26,25 Using transgenic mouse strains carrying specific cell surface markers in their lymphocytes, it was possible to selectively eliminate the host-type T cells from the tolerant animal.7,25 If this cell-depletion was performed immediately after cell transfer, the tolerance state was broken and indicator grafts were readily rejected by the transferred non-tolerant lymphocytes.7,25 If, however, the host cells were allowed to coexist with those adoptively transferred for 4-6 weeks, then tolerance was maintained even after the depletion of the host cells.7,25 The remaining cells were nevertheless fully competent to reject an unrelated graft. Not only were they unable to reject a

Grafts rejected

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