ROLE OF THE THYMUS IN TRANSPLANTATION 

 TOLERANCE AND IMMUNITY 



J. F. A. P. Miller 



Chester Beatty Research Institute, Institute of Cancer Research: Royal Cancer 

 Hospital, London 



It has often been debated whether the thymus really plays any 

 significant part in immunological processes. The intact thymus 

 has not been shown to produce antibody in immunized animals 

 nor does it undergo the histological changes observed in lymph 

 nodes and spleen following the parenteral administration of 

 antigens (Fagraeus, 1948; Askonas and White, 1956). Further- 

 more, thymectomy in the adult animal has been associated with 

 slight or no significant depression of antibody production. On 

 the other hand, there are hints from experimental and clinical 

 observations that the thymus may play some role in the control 

 of the immune response. Thus, it is well known that the thymus 

 is the major lymphoid organ in perinatal life at a time when the 

 animal is most sensitive to external modification of the immuno- 

 logical system. In acute infections, when presumably the need 

 for antibody production is great, the thymus undergoes rapid 

 involution and in patients with acquired agammaglobulinaemia 

 there is often the simultaneous occurrence of benign thymomas. 



Our interest in the thymus arose from observations made 

 independently in this laboratory (Miller, 1959) and in two other 

 laboratories (Gross, 1959; Levinthal, Buffett and Furth, 1959) 

 that thymectomy in mice as late as one month of age would 

 prevent viral induction of lymphocytic leukaemia without 

 actually removing the virus that had been introduced at birth. 

 This prompted us to do certain experiments which required the 



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