Transplantation models using the regional lymph node.

Several transplantation models, using the regional lymph node, to study the transplantation reaction in strictly defined and simple conditions were devised. Lymphoid cells were transplanted to inbred rats and mice at the sites drained by one regional lymph node; the experimental design was chosen so as to permit theoretically a one-way reaction, either the host-versus-graft (HVG) or the graft-versus-host (GVH) reaction. The changes in the lymph nodes draining the site of cell injection (weight increase, histology, lymphocyte activation) were very similar in both transplantation reactions. They were ascribed to a humoral mediator released upon the contact of lymphoid cells from two genetically different individuals. The direct demonstration of a mediator which is capable of activating the regional lymph node in vivo introduces some new aspects into the process of sensitization after transplantation.