G. J. V. NOSSAL AND LOIS LARKIN 



recipients were adequate hosts for the antibody-producing cells, and antibody 

 developed in their serum. However, in the neonatal recipients, the trans- 

 ferred cells did not make antibody. Apparently the environment of the 

 neonatal animal is inimical to the initiation of a primary antibody response, 

 although as was seen earlier, there is nothing in the environment inimical 

 to antibody production per se. These results are in agreement with findings 

 described by Dixon and Weigle^. Similar results were obtained when non- 

 irradiated neonatal rats were used as recipients. However, when a large 

 number of normal spleen cells was injected into the neonatal recipients either 

 before, with, or some days after the stimulated spleen cells, some antibody 



<10 



4 6 8 10 12 

 Days after injection 



14 16 17 



Figure 3. Transfer of normal spleen cells stimulated in 



vitro: • — • adult irradiated recipients; ■ ■ 



neonatal irradiated recipients 



production did result. Conversely, when neonatal spleen cells were trans- 

 ferred to X-irradiated adult recipients, after suitable stimulation in vitro, 

 some antibody production resulted®. 



The full implications of this work are not clear as yet, but it appears that 

 for the first step in the chain of events leading to antibody formation to take 

 place, the cells concerned must be placed in a suitable environment, such as 

 is provided by an adult animal. If this first step has already been taken, 

 then the process of antibody production can continue quite satisfactorily 

 even in the environment of the neonatal animal, and, to a lesser extent, in 

 tissue culture. The nature of this essential environmental factor is still 

 entirely obscure, and is being investigated further at the moment. 



The next question to interest us was the possibility of isolating a 'clone' 

 of antibody-producing cells in the immunologically neutral environment of 

 the neonatal rat or the X-irradiated adult rat. The experimental procedure 

 was as follows: recipients were inoculated intraperitoneally with stimulated 



239 



