Lymphocytes: Origin, Structure, aud Interrelationships 3 



flammatory reactions. The fact that some type of blood cell (lymphocyte?) 

 can even become an epithelial-like cell in tissue culture has been described 

 and illustrated by Berman. 18 



An intriguing and plausible concept is that of Trowell 19, -° who suggested 

 that reticulum cells containing phagocytosed lymphocytes may develop to the 

 more rounded precursors of lymphocytes while still containing visible re- 

 mains of ingested lymphocytes. He felt this concept would explain the life- 

 span data of Hamilton- "' and others 21 " 25 and offers this morphologic explana- 

 tion of reutilization of lymphocytes as well as of lymphocytogenesis. With 

 this in mind, he is prepared to dispense with the primitive or undifferentiated 

 reticulum cell and to propose instead that there is but one type of reticulum 

 cell. 



This concept seems refreshing and acceptable, but whether or not it covers 

 all situations is difficult to say. Yoffey 26 is not prepared to endorse this whole- 

 heartedly because phagocytosis, lymphocytolysis, and lymphocytogenesis are 

 unequally represented in germinal centers and other areas of lymphocyto- 

 genesis, and the association of macrophages and mitotic figures is not clear- 

 cut. 



Here it should be emphasized that for many years Downey stressed that 

 reticular cells had diverse functions (phagocytosis, storage, support, and lin- 

 ing as well as hematopoiesis) , but he also considered the cells sufficiently 

 versatile to do more than one thing at once. Examples of this include: the 

 ability of the Gaucher cell to phagocytose erythrocytes and contain hemosid- 

 erin as well as to store kerasin 27 and the ability of the hematopoietic reticular 

 cells of leukemic reticuloendotheliosis to be actively phagocytic. 28 ' 29 Dow- 

 ney's illustrations of the "histiocytes" of subacute bacterial endocarditis show 

 the transformation of this type of cell to a monocyte. 29 One of the reticular 

 cells (Fig. 27 in Reference 29) contains a dark body which might well be nu- 

 clear debris. 



I have spent many years wondering what the macrophages of the bone mar- 

 row do with the many things they ingest in toto (erythrocytes, normoblasts, 

 neutrophils, lymphocytes, platelets, and occasionally other cell types as well 

 as iron, melanin, and unidentified stainable materials) . My preoccupation 

 with storage iron"' 031 and melanin 30, 32 has kept me from investigating the 

 other cytoplasmic contents of these macrophages sufficiently thoroughly to 

 draw definite conclusions concerning disposition of these cytoplasmic con- 

 tents. (In the case of reticular cells containing phagocytosed erythrocytes or 

 iron, I have assumed that the reticular cells were processing the red cell or the 

 iron for reutilization. In the case of reticular cells containing- numerous neu- 

 trophils and their autolyzed remains — in the absence of agranulocytosis — I 

 have tried unsuccessfully to correlate this with hyperuricemia and have 



