The transplantation of normal tissues: with special reference to auto- and homotransplants of thyroid and spleen in the anterior chamber of the eye, and subcutaneously, in guinea-pigs

The transplantation of tissues raises many yet unsolved problems of fundamental interest, and is of potentially great clinical importance, especially in endocrinology. The present investigation is concerned with three main problems: the immunological reactions associated with the growth of homografts in the anterior chamber of the eye and subcutaneously; the role of the reticulo-endothelial system in the resistance to homografts; and the applicability of Halsted’s principle to auto- and homografts of endocrine tissue, and the mechanism involved. Four groups of experiments are described. In group I, a preliminary study of auto- and homografts of thyroid in the guinea-pig, it is shown that, if a total thyroid deficiency is produced in the host, autografts are uniformly successful both in the anterior chamber and subcutaneously, whereas homografts are usually successful in the anterior chamber but rarely so when made subcutaneously. Halsted’s principle holds good for anterior chamber grafts whether auto- or homografts, i.e. the proportion of successful grafts increases pari passu with the degree of thyroid deficiency produced in the host, but appears to be less applicable to subcutaneous autografts. Some light is thrown on the mechanism of Halsted’s principle by the observation that successful anterior chamber grafts can be obtained in non-thyroidectomized hosts if injections of pituitary thyrotrophic hormone are given. The experiments of group II are concerned with the immunological phenomena relating to thyroid homografts. It is shown that a subcutaneous homograft of thyroid in the guinea-pig is demonstrably antigenic and the same is true of a homograft in the anterior chamber provided this is undergoing destruction. The state of immunity induced is general and extends to the anterior chamber. The existence of a state of immunity induced by a homograft is shown by the diminished chance of a subsequent homograft ‘taking’, but ‘immunization’ (by means of a subcutaneous graft) of an animal which already has a homograft established in the anterior chamber does not appear to modify the behaviour of the latter. In group III it is shown that a homograft transferred after some months from the anterior chamber to a subcutaneous site is more likely to survive than a primary subcutaneous homograft. It thus appears that when a homograft is established in the anterior chamber for a sufficiently long time a process of adaptation occurs as between graft and host. The experiments of group IV relate to the behaviour of auto- and homografts of spleen in the anterior chamber, and of simultaneous thyroid and splenic grafts. It is shown that the chances of success of a thyroid homograft in the anterior chamber are greatly reduced if the latter is provided with reticulo-endothelial tissue in the shape of a simultaneous autograft of spleen, but that a simultaneous homograft of spleen from the same donor has little or no deleterious effect. The mechanism of this phenomenon has not been fully elucidated but would appear to be either cellular, humoral or a combination of the two.