Comparative Studies on Autoplastic Lymph Node and Thymus Transplants.

Abstract

Studies by numerous investigators on the histogenesis of the thymus gland have failed to clear up the origin and biological significance of the small thymic cell. In order to secure additional data concerning the origin of these cells, the method of autoplastic thymus transplantation with careful histological studies of the daily regenerative changes which take place in the growing transplants was utilized. 1 It was concluded from these experiments that the small thymic cell in the rat arises from the reticular epithelium.

In an effort to gather further evidence on this much mooted question, the regeneration of a series of lymph node transplants has been studied and compared with transplants of the thymus in rats of the same age, sex and strain. To our knowledge no detailed nor extensive studies are available concerning successful transplantation of lymph nodes. In our studies, young albino rats were used. Pieces of inguinal lymph nodes, approximately 8 mm. in diameter were planted into prepared pockets in the abdominal wall. The presence of infection in these nodes in young rats is infrequent.

At the end of the first 24 hours the lymph node transplants show almost complete destruction of both reticular and lymphocytic elements except for a small zone of well preserved lymphocytes at the periphery, with invasion by polymorphonuclear leucocytes, rapid phagocytosis and marked congestion of the surrounding blood vessels. At 48 hours there is striking evidence of proliferation of the reticular cells from the outer zones, with extension of these elements in finger-like processes toward the center of the transplant. In the outer zone of regenerated reticulum are seen many newly formed lymphocytes. During the third day mitotic figures are numerous. Small lymphocytes which are present as early as 24 hours increase in the outer zone of the transplant.