change from allograft rejection. Serial lung 
biopsies are impractical, and a precise method 
for assessing the degree of lung allograft rejec- 
tion is badly needed. 
It was demonstrated by Blumenstock and co- 
workers that well-matched animals rejected 
lung allografts less readily than did mis- 
matched animals.'^o 
Lung Allotransplantation for Treatment of 
Induced Pulmonary Hypertension 
It was the large number of patients with res- 
piratory insufficiency who first served to stimu- 
late investigation of lung transplantation. Yet, 
an additional problem of less magnitude but of 
considerable clinical importance is that of pul- 
monary hypertension, often associated with car- 
diac lesions. Frequently, the patient has an intra- 
cardiac lesion which could be corrected satisfac- 
torily with present operative techniques, were 
it not for the severe pulmonary hypertension 
which exists and which would result in an un- 
acceptably high mortality rate following repair 
of the intracardiac lesion using cardiopulmo- 
nary bypass. Furthermore, some patients have 
severe primary pulmonary vascular hyperten- 
sion, even in the absence of intracardiac lesions. 
This pulmonary hypertension can produce right 
heart failure and terminate in death. However, 
if lung allotransplantation were a safe and 
dependable procedure, many cases of pulmo- 
nary hypertension which would otherwise 
terminate fatally could be treated effectively. 
The usefulness of lung allotransplantation 
for the reduction of induced pulmonary hyper- 
tension was studied in our laboratory.'^^ First, 
