Role of the Lymphocyte in Antibody Formation 93 



synthesis in the recipients because: (1) viability was a necessary criterion tor 

 the donor cells to produce antibody, i.e., no immune response was associated 

 with the transfer of fro/en-thawed or heat-killed cells; (2) the recipient rab- 

 bits were exposed to 400 r whole body x-radiation which rendered them 

 incapable of responding to bovine serum albumin; (3) the prompt elimina- 

 tion of antigen and the appearance <>l circulating antibody were typical of 

 a secondary response, as would be expected from the hyperimmunized donor 

 cells; (4) the quality of the antibody as measured by initial combining ratios 

 was definitely that of secondary antibody : and (5) the amount of antibody 

 observed in the recipients was much more than was observed in normal 

 rabbits making a primary response to 1.5 mg. of bovine serum albumin. 03 



The quantity of antibody synthesized also enters into consideration of the 

 question of which cell type was basically responsible for the antibody syn- 

 thesis. Since the antibody made by the transferred cells in the recipient was 

 comparable on a molecule per cell ratio to that made in the most active in- 

 tact hyperimmunized rabbits, it seems most reasonable to assume that the 

 cell responsible for the synthesis of antibody was the preponderant cell, the 

 lymphocyte. To attribute the synthesis of so much antibody to the relatively 

 few T nonlymphocytes of the transferred pools seems unreasonable, since this 

 would mean that the macrophages, reticuloendothelial cells, and plasma 

 cells made many times their own wet weight of antibody in the eight-day 

 period. A significant increase in the numbers of these cell types after transfer 

 seems unlikely in view of the paucity of detectable mitoses in the cell trans- 

 fer sites. 



The failure to find mitoses in the transferred cells is in contrast to obser- 

 vations by Doctor (loons and his group who found considerable mitotic 

 activity in the plasma cell series during the process of antibody formation in 

 lymph nodes of the intact rabbit. 1 ' 4 Similar to our cell transfer findings, less 

 mitotic activity was noted by Fagraeus in cultured tissues producing anti- 

 body than in the same tissues of intact animals producing antibody. 14 Thus, 

 while proliferation of antibody-containing cells during the course of an 

 immune response may occur in the usual situation, it is apparently not an 

 essential feature of the secondary antibody response made by transferred 

 cells. 



Since the immunologic evidence indicated that the transferred cells syn- 

 thesized the antibody observed in the recipient of live cells, and since the 

 decrease in lymphocytes observed between the second and fifth days after 

 transfer was paralleled by an increase in antibody-containing cells of the 

 transitional and preplasma types, and since S 35 -uptake studies on intact 

 animals have shown that the peak rate of antibody synthesis occurred during 

 approximately the same period, days 3 to 6 after the injection of antigen, 65 



