Histochemistry of Lymphocytic Tissue in Malignant Lymphomas 195 



(1) identification of specific cells by their enzyme activity and (2) a study of 

 the possible differences in metabolism of neoplastic cells as contrasted with 

 their normal counterparts. The currently popular concept of enzyme adapta- 

 tion and observations indicating an apparent tendency toward enzyme dele- 

 tion in malignant neoplasms are evidences of the potential importance of 

 the latter. 1 



HYDROLYTIC ENZYMES IN NORMAL LYMPHOID CELLS 



Table 16-1 summarizes the hydrolytic ezyme activity of the normal lym- 

 phoid cells. As pathologists our belief is that lymphoid elements represent 

 distinct morphologic units and that differences in morphology will probably 

 be accompanied by functional differences. 2 



Lymphocytes. The lymphocyte, the predominant nodal cell, manifests 

 only probable acid phosphatase activity but no esterase, alkaline phosphatase, 

 5-nucleotidase, phosphamidase, 3 or leucine aminopeptidase. We have not 

 studied ^-glucuronidase in humans. Studies of blood smears and lymph node 

 imprints have confirmed the presence of slight acid phosphatase activity in 

 50 to 90 per cent of normal lymphocytes. 



Histiocytes. Histiocytes in all locations in the lymph node manifest 

 strong esterase, acid phosphatase, and phosphamidase activity. 3 Slight leucine 

 aminopeptidase activity is also present, while studies by others have re- 

 vealed /^-glucuronidase as well. 5 Blood monocytes, like histiocytes, contain 

 considerable acid phosphatase and esterase, but we have not studied enzymes 

 other than these and alkaline phosphatase. Germinal center cells reveal 

 moderate 5-nucleotidase activity' 1 but are otherwise unreactive, while capil- 

 lary endothelium is strongly positive for alkaline phosphatase only. 



Lymph Node Follicles. When the normal lymph node follicle was 

 stained to demonstrate nonspecific esterase, the isolated histiocytes were posi- 

 tive (black) while germinal center cells were negative. Study of the same 

 follicle in a preparation demonstrating acid phosphatase activity revealed 

 that activity restricted to histiocytes as manifested by black precipitate. 

 When stained to demonstrate 5-nucleotidase, the cells of the germinal centers 

 were positive (black), while the areas within them, where histiocytes are 

 located, were devoid of activity. 



Other Lymphoid Elements. When a lymph node showing the typical 

 pattern of sinus hyperplasia was stained to demonstrate esterase, the histio- 

 cytes lining the peripheral lymph sinus stained strongly. In a similar section 

 stained to demonstrate acid phosphatase, 7 the sinus histiocytes contained con- 

 siderable bright-red precipitate. Leucine aminopeptidase activity in histio- 

 cytes was shown by the red precipitate in sinus lining cells. In sections of 

 spleen stained to show acid phosphatase, the red pulp manifested intense 



