REACTIONS OF THE GRAFT VERSUS HOST (GVH) TYPE

Abstract

Summary Normal lymphoid cells obtained from animals that are phylogenetically unrelated or only distantly related to the chicken do not initiate graft versus host reactions when introduced into chicken embryos. Such cells are capable of mounting a reaction against the embryo if the donor animal is first immunized with chicken tissues. However, the reaction produced by immune xenogeneic lymphoid cells has a different pathogencsis to that produced by normal allogeneic cells. The transfer of adult blood leucocytes to syngeneic embryos will confer on the embryo the ability to reject transplanted allogeneic tissue, but will not confer on the embryo the ability to make antibody or to reject the transplants of some xenogeneic tissues. The latter type of transplant can be rejected if cells allogeneic with respect to the graft are introduced into the embryo. Allogeneic transplants are only rejected by embryos treated with adult blood leucocytes if the transplant contains a relatively large component of reticular tissue. Treatments, such as γ‐írradiation, that reduce the amount of reticular tissue in the graft protect it from transplantation damage in treated embryos. The in vitro interaction between populations of lymphocytes obtained from different animals has the same specificity as graft versus host reactions in so far as lymphocyte populations obtained from sheep are not stimulated by lymphocytes obtained from a different species of animal such as the rat or goose, but are stimulated by allogeneic lymphocytes. The treatment of one population of sheep lymphocytes with γ‐rays will destroy their capacity to stimulate allogeneic lymphocytes without affecting the antigenicity of the lymphocytes. It is suggested that the ability of an animal to distinguish between “self” and “not‐self” components may operate at two distinct levels; one involves the recognition of foreign antigens, and the other the recognition of cells derived from genetically related but not identical animals.