INDUCTION OF SPECIFIC TOLERANCE IN ADULT 

 RATS BY THE METHOD OF PARABIOSIS* 



B. Nakic, a. Kastelan and N. Avdalovic 



Institute of Physiology, Faculty of Medicine, University of Zagreb 



The most important contribution to tissue transplantation 

 research since Meda war's demonstration (1944) that homograft 

 rejection is an immunological phenomenon, was the discovery by 

 Billingham, Brent and Medawar (1953) that the body's immuno- 

 logical defence mechanism can be artificially overcome by inocu- 

 lation of cells from an adult donor into immature recipients. 

 In the same year Hasek (1953) described another experimental 

 model known as "embryonic parabiosis" whereby artificial syn- 

 chorial anastomoses were established between two bird embryos. 

 Both methods were successful in inducing specific tolerance to 

 subsequent skin homografts. 



For some time it was believed that induction of tolerance to 

 living tissue was limited by the so-called "adaptive period" 

 which in most species ends around the time of birth. The first 

 indication that it may not be so and that specific tolerance could be 

 artificially induced in adult animals as well came from the radio- 

 biologists. Main and Prehn showed (1955) that mice receiving a 

 lethal dose of X-rays and protected with bone marrow from an 

 Fi hybrid derived from the irradiated and a foreign strain, will 

 subsequently tolerate skin homografts from the foreign parent 

 strain of the Fj hybrid. Later on, many others showed that specific 

 tolerance to homografts (Trentin, 1956; Barnes et aL, 1958) or 

 even heterografts (Zaalberg, Vos and van Bekkum, 1957) can be 



* This work has been supported by grant no. 2919/2 from the Federal Scientific 

 Fund (Belgrade). 



328 



