MECHANISM OF ANTIBODY FORMATION 77 



intensification of the protein production has occurred in reticulo- 

 endothehal cells, incited by the great antigen doses injected. From a 

 functional point of view, this development culminates in the formation 

 of the immature plasma cells. Maturing of the latter into plasma cells 

 marks the transition to a less active state, and, therefore, the mature 

 plasma cell represents the final link in a chain of development, a cell 

 which has already passed the stage of its great functional intensity. 

 Fagraeus (1948) concluded that "reticulo-endothelial elements under 

 the conditions described, produce antibodies, thereby develofing into 

 a type of cell xvith the morphological characteristics of the plasma cell." 

 She found no evidence which would directly favor the participation of 

 the lymphocytes in the formation of antibodies.* 



C. THEORIES ON THE MECHANISM OF ANTIBODY 

 FORMATION 



In Part I, experimental data were cited to indicate that the role of 

 antigen in the production of antibody might be one of catalysis. It 

 was further stated that naturally occurring iso-antibodies, agglutinins 

 against bacteria, and red blood cells, precipitins against animal and 

 plant proteins and toxins appeared to be serum globulins. These would 

 emphasize not only the fact that the normal serum and antibody 

 globulins are closely related but also the fact that the site of their forma- 

 tion might be identical. 



At the present time, we are handicapped by the lack of precise 



*Fagraeus (1947) found that the thymus, where the chief production of lympho- 

 cytes takes place (Andreasen and Ottesen, 1945), has an insignificant antigen- 

 phagocyting capacity, and lacks entirely the capacity to form antibodies in vitro. 

 Harris, Rhoads and Stokes (1948) also studied the function of thymus in relation 

 to the formation or retention of antibodies. They likewise found that the thymus 

 did not play a demonstrable role in the formation of antibodies by the young rabbit, 

 or in the retention of antibodies derived by the fetus from the maternal circulation. 

 The formation of antibodies by spleen was also comparatively studied. They found 

 slight evidence of formation of antibodies in the spleen following subcutaneous 

 injections, but high antibody- titers were demonstrated in the spleen extracts following 

 intravenous injection of antigens. This difference was explained by assuming that 

 "the subcutaneously injected rabbits may well have formed the bulk of their anti- 

 body to the Shigella in the lymph nodes draining the site of injection, the spleen 

 being stimulated only by the fraction of soluble antigen-specific material which 

 reached it via the blood stream. In the intravenously injected animals, on the other 

 hand, the spleen could have received a major portion of the injected antigen and 

 would thus have played a relatively greater role in the total antibody response of 

 the animal." 



