The Histological Changes in Immunologically Tolerant Lymphoid Tissue

The histological features of the regional lymph node draining a skin homograft have been examined in normal and tolerant recipients. The response of this node was morphologically identical in normal and specifically tolerant hosts, the most important feature being the appearance of medullary cords packed with intensely pyroninophilic cells. Furthermore, a similar response was observed in the regional lymph nodes of (DA×Lewis) F_1 hybrids bearing DA skin grafts of which they were ”genetically tolerant”. It was concluded that the failure of graft rejection in tolerant rats could not be attributed to an absence of reactivity to the grafts on the part of the lymphoid tissue of the host.