ANTffiODY FORMATION 



1000 

 700 

 500 



300 



T i \ \ r 



1 r 



• -CONTROLS 



O - THYROIDECTOMIZeO 



A -THYROXIN-TREATEO 



5 6 7 8 



TIME (WEEKS) 



10 



12 13 



Figure 3. Circulating antibody levels in surgically thyroidectomized, thyroxin- 

 treated, and untreated control rabbits immunized with BSA plus Freund's adjuvant 

 (10 mg BSA per kg body wt) at time zero. 



manner. Maximum utilization of the experiment could be had in this 

 way, and information relative to the time course of re-adaption to 

 the lower altitude obtained. 



After primary injection, the animals at high altitude had levels 

 of circulating antibody approximately 60 per cent higher than con- 

 trols, and were significantly different. After the secondary challenge, 

 the group previously exposed to high altitude had levels of circulating 

 antibody approximately 35 per centhigherthan controls, even though 

 they had been residing at the lower altitude for about six weeks. A 

 third immunization, 22 weeks after descent to lower altitude, showed 

 no difference between the two groups. In this experiment, the time 

 course of response to the antigenic stimulus was similar for both 

 groups. The maximums reached, however , by the high- altitude group 

 were greater both while at the mountain and 6 weeks after returning 

 to the lower altitude. 



95 



