TRAPANI 



A study was made of passive and active immunization in rabbits 

 which were either surgically thyroidectomized or treated with thy- 

 roxin. The half- life of passively administered antibody in thyroidec- 

 tomized, thyroxin- treated, and controls (Fig. 2) was: 8.9* 0.4, 3.8 ± 

 0.2, and 4.7 ± 0.2 days, respectively. 



Similarly prepared groups of rabbits were actively immunized 

 with BSA (10 mg per kg body weight) in Freund's adjuvant. Figure 

 3 displays the data obtained from the experiment. The circulating 

 antibody level in the thyroidectomized group rises gradually and ap- 

 proximates the control level at about 14 weeks after immunization. 

 The thyroxin- treated group, on the other hand, not only had an in- 

 itially higher level of circulating antibody, but also displayed 

 measurably increased amounts of antibody 3 days after immuniza- 

 tion. This early response was not present in either of the other 

 groups. After the initial high level of circulating antibody in the 

 thyroxin- treated group, there was a decline to levels below those of 

 controls, and then a second increase. Thus, there is a similarity 

 between hyperthyroid and cold exposed animals in terms of an in- 

 creased rate of proteinturnover. However, the net immune response 

 after active immunization shows little similarity between hyper- 

 thyroid and cold exposed rabbits. 



Since experiments concerned with thyroid activity did not clarify 

 the results obtained with cold exposed animals, we next investigated 

 the role of the adrenal gland on the immune response. One reason 

 for this approach was the observationthathigh- altitude acclimatized 

 rabbits showed an increased immune response, and animals under 

 these conditions exhibit an increased adrenal activity. 



Figure 4 shows the results of active immunization of rabbits ac- 

 climatized to 14,150 ft. at the Summit Laboratory of the Inter- 

 University High Altitude Laboratory at Mount Evans, Colorado, 

 Immunization was accomplished with a single intravenous injection 

 of 10 mg BSA per kg body weight. The animals were bled periodi- 

 cally for the next 5 weeks and then returned to Denver (altitude = 

 5,280 ft.) where further samples were taken. After circulating anti- 

 body had reached low levels, the animals were given a secondary 

 intravenous challenge with 10 mg BSA per kg body weight. Sixteen 

 weeks later, a third immunization dose was given in the same 



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