248 HILDEMANN, LINSCOTT AND MORLINO 



assay provides a satisfactory basis for an overall measurement of 

 varying degrees of runt disease over a broad range of ages. 



The general predictive value of the weight-gain assay employed 

 was borne out by individual weights in the series that received 

 2 X 10^ cells. All animals that later died showed individual 

 weights well below normal from 9-1 1 days on, although many 

 eventual survivors achieved weights approaching or within the 

 normal range by three weeks of age. 



A more detailed but laborious assay of graft-induced trans- 

 plantation disease, first devised by Simonsen and co-workers 

 (1958), involves the determination of body, spleen and liver 

 weight indices of graft reaction. The method is based on the 

 fmding that with many combinations of inbred mouse strains, 

 there is an increase of spleen and liver weights in conjunction with 

 failure to gain body weight among neonatal mice under immuno- 

 logical attack. This approach, of course, requires that injected 

 Htters be killed at a given time, optimally at some 9-15 days after 

 injection. Evaluation of histopathological changes during the 

 syndrome was also made concurrently in the present study. 



Application of this *' organ-enlargement" assay to our system 

 provided insight into the immunopathological effects of blood 

 lymphocytes compared with those of the mixed populations of 

 leucocytes employed in previous mouse studies. Four litters of 

 A/Jax mice totalling 12 experimental animals were killed at 14 and 

 15 days of age. These animals had been injected by the intra- 

 cardiac route with 0-9-1 • million adult C57BL/6 small lympho- 

 cytes at birth. Whole body weights were taken, gross pathological 

 changes noted, and spleen, hver and kidney weights recorded for 

 each animal prior to fixation of these organs for subsequent 

 sectioning and staining with Maximo w's haematoxyhn-eosin 

 azure II stain (spleens) or haematoxylin and eosin. From these 

 data, indices of graft-versus-host reaction were computed along 

 with the means and confidence hmits for each set of values. These 

 results are detailed in Table II. The indices are quotients represent- 



