VII 



MESENCHYMAL CELL FUNCTION 

 IN IMMUNITY 



I. Lymphocyte and plasma cells 



There is no serious objection to the view that the main contri- 

 bution of circulating antibody comes from cells with the 

 histological character of immature plasma cells (Fagraeus, 

 1948) and that mature plasma cells may contain high con- 

 centrations of antibody. Probably most would agree that 

 there is no indication that plasma cells have any other 

 function than to produce gamma globulin and many would 

 go further and say that the presence of plasma cells indicates 

 the production of one or other kind of antibody. 



The part played by the lymphocyte is, however, less 

 widely accepted. The ubiquity of the small lymphocyte 

 seems to demand that it is a cell of important function and in 

 the clonal selection theory of antibody production it plays 

 a central role as {a) the carrier of the genetic ' information ' 

 determining antibody specificity and the potential parent of 

 the plasma cells which are responsible for active production 

 of antibody, and {b) the mediator of the functions of cell- 

 borne antibody. The evidence for such a central function in 

 immunity is still inadequate in the view of most commenta- 

 tors. The most recent critical discussion of the cells of the 

 reticular tissue is that of Marshall (1956). He states bluntly 

 that ' the fate and functions of the lymphocytes . . . are mainly 

 unknown'. The chief difficulties are [a) that all functional 

 studies must be made on complex cell populations which will 

 normally contain a proportion of plasma cells and macro- 

 phages that may be responsible for the observed effects and 

 (b) that it has proved very difficult to provide a satisfactory 

 interpretation in terms of genetic sequence and physio- 



107 



