330 . B. NAKIC, A. KASTELAN AND N. AVDALOVIC 



"parabiotic disease" (Nakic and Silobrcic, 1958). Tested in 

 extremis, these parabionts were found to be chimeras (Nakic and 

 Silobrcic, 1962). 



The characteristic symptoms of "parabiotic disease" were 

 wasting, diarrhoea, anaemia and general lymphoid atrophy in an 

 animal tolerant of the skin graft from its parabiotic parmer. 

 These symptoms were never observed in a parabiont that had 

 successfully rejected the cross-graft. This close relationship of 

 tolerance to the disease was absent in parabionts challenged with 

 the graft from the third strain (Nakic and Silobrcic, 1962). 

 Symptoms of the disease appeared several days after complete 

 breakdown of the graft ; even when parabionts fell ill with a graft 

 that was still preserved, the symptoms continued for several 

 days following rejection of the graft. Thus it appeared that once 

 the symptoms of " parabiotic disease" had set in, inhibition of the 

 immune reaction became specific, the sick animal being quite 

 capable of differentiating between the cross-graft and the graft 

 from the third party. 



Because of the close relationship of the disease to tolerance and 

 the striking similarity between "parabiotic disease" and "para- 

 biosis intoxication" on the one hand and conditions such as 

 "runt disease" and "secondary disease" on the other, we have 

 included "parabiotic disease" or "parabiosis intoxication" in the 

 now large family of graft-versus-host reactions (Nakic and Silo- 

 brcic, 1958). Since it seems that the term "parabiosis intoxication" 

 may cover several phenomena (Eichwald et al, 1961) we suggest 

 that the term "parabiotic disease" be reserved to denote the graft- 

 versus-host reaction in parabionts. 



The susceptibility to "parabiotic disease" has been found to 

 fall sharply in parabionts two months of age or older (Nakic 

 et al, 1961). Younger hosts, unable to reject the cross-graft, all 

 succumb to "parabiotic disease". The relation of age to suscep- 

 tibility to graft-versus-host reaction has already been described by 

 Cock and Simonsen in chicks (1958) and by Billingham and 



