IMMUNOLOGICAL STUDIES ON IRRADIATED ANLMALS 



spleen cells. A consideral)lc piojjortion f)f these found their way to the 

 spleen of the recipient animal, and diflcrentiated there into antibody- 

 producing cells. The recipients were killed two weeks later, their spleens 

 were removed, restimulated in vitro, and injected into further recipient 

 animals, and so forth. The basic plan of these experiments was rather 

 similar to that of the experiments by Simonsen, cited earlier. 



Figure 4 demonstrates the cflcct of passage of stimulated spleen cells 

 through a series of neonatal rats, antigenic stimulation in vitro preceding each 

 passage. The controls, given either antigen alone, or unstimulated adult 



5.242.880 



1.310,720 



327.680 



2: 81.920 



>. 



T3 

 O 

 .O 



C 

 ID 



E 



I 



20.480 



5.120 - 



1.280 



320 



80- 



20 



<10 



2nd 3rd Ath 5th 

 Passage 



Figure 4. Serial transfer of immune spleen 

 cells to neonatal recipients: ■ — ■ immune 



spleen; • • normal spleen; X — X 



antigen alone 



spleen cells, elaborated virtually no antibody. The recipients of immunized 

 spleen cells developed high titrcs of antibody for the first three passages, but 

 then the titres fell off rather sharply. However, some immunologically com- 

 petent cells were still present even after five passages. In Figure 5 the results 

 of serial passage through sub-lethally irradiated adults are depicted. Here, 

 the results were not quite so easy to interpret, because the control animals 

 did have a partial response to the injection of antigen alone, and on passage 

 developed quite high titres. However, it can be seen that serial passage of 

 cells from immune donors to X-irradiated recipients is followed by per- 

 sistent antibody-forming activity for at least six passages. Here, also, the 

 difference between neonatal and adult environment is evident. The adult 

 animal can support the initiation of the primary response, as evidenced by 

 the good titres obtained on first and subsequent passages of normal spleen 



240 



