Cytochemistry of tJie Lymphocytes 35 



The Feulgen nucleal reaction has been combined with microspectro- 

 photometry in order to determine quantitatively the amount of DNA in 

 normal and leukemic lymphocytes. 05 - 7!) ' 80 These data 05, 80 indicate that the 

 normal lymphocytes of the blood and the majority of those of lymphatic 

 tissue contain the diploid amount (2n) of chromatin as do other somatic 

 cells. Some of the lymphoid cells in lymphatic tissue possess intermediate 

 values of chromatin between the diploid and tetraploid (4n) amount sug- 

 gesting a premitotic build up of DNA in the immature lymphocytes. 80 In 

 six patients with chronic lymphocytic leukemia, the lymphocytes were found 

 to contain the normal (2n) amount of chromatin, while those from three 

 patients with chronic lymphocytic leukemia and four of five patients with 

 acute lymphocytic leukemia were found to contain between the normal 

 diploid and the tetraploid amount of chromatin. 80 These observations sug- 

 gest that most of the lymphocytes in chronic lymphocytic leukemia are in- 

 termitotic, while those of acute lymphocytic leukemia are either in the 

 process of mitosis with premitotic synthesis of DNA or actually may exhibit 

 polyteny. 80 Confirmation of these observations is awaited with great interest. 



Pentose Nucleic Acid (PNA or RNA). The basophilic staining property 

 of the cytoplasm and nucleoli of various blood cells following staining with 

 certain basic dyes has been recognized for many years. 30 ' 49, 59, 8G ' no Both 

 microspectrophotometry and selective abolition of basophilia with the en- 

 zyme ribonuclease 22 have indicated that this basophilic substance is a 

 nucleoprotein, namely RNA. Histochemical studies on normal lymphocytes 

 (Figs. 3-19, 3-20) and on those from various hematologic dyscrasias have 

 shown that cytoplasmic basophilia 11 - or more specifically RNA varies in- 

 versely with the age of the lymphocyte. This substance is formed in large 

 amounts in the lymphoblasts and gradually decreases during the maturation 

 of the lymphocyte. 1 ' 112 It seems probable that the RNA plays an important 

 role in the formation of cellular proteins and globulins. 80 After injection 

 of antigen into an animal, the RNA content of the immature cells increases 

 first in the altered reticular cells then in the young lymphocytes while the 

 DNA content remains constant. 30 ' 49 



Methyl green-pyronin has been widely employed in histochemistry for the 

 simultaneous visualization of DNA and RNA. 78 Methyl green acts as a 

 selective stain for highly polymerized DNA present in the chromatin of the 

 cell, while pyronin has an affinity for RNA of the cytoplasm and nucleoli. 

 The RNA nature of the cellular substances is confirmed by selective extrac- 

 tion with ribonuclease. Results obtained by the methyl green-pyronin 

 method on the lymphocytes 30, 49 ' 7S in the blood and lymphatic tissue are in 

 agreement with those described earlier. 



Differences in methyl green stainability between granulocytes and lympho- 



