34 The Lymphocyte and Lymphocytic Tissue 



HISTOCHEMISTRY 



Recent advances in the field of histochemistry have added considerably to 

 our knowledge of the chemical structure of the lymphocyte and have given 

 some insight into the chemical alterations in these cells in disease. Histo- 

 chemistry not only provides a method for chemically identifying and classify- 

 ing various normal and abnormal cells but provides one of the most im- 

 portant approaches for determining the underlying causes of disease and 

 cellular differentiation. Few detailed studies have been made concerning 

 the histochemistry of the lymphocyte either in the normal or diseased con- 

 ditions. Although lymphatic tissues have been subjected to a large number 

 of histochemical procedures, all too frequently observations are histologic 

 rather than cytologic in nature. Not infrequently histochemical reactions 

 are described as being either present or absent in a given cell or tissue, and 

 the reactive substance is not localized to the morphologic structures within 

 these cells. Considerable data have been derived from the study of leukemic 

 cells without attempting to correlate these findings with comparable cells 

 in the normal condition. These facts coupled with the development and 

 improvement in histochemical procedures and inherent difficulties in vari- 

 ous methods have caused considerable variations in the literature concerning 

 the histochemical characterization of the lymphocyte. An attempt has been 

 made to summarize briefly the most important observations concerning the 

 histochemistry of the lymphocyte in health and disease. 



Nucleoproteins 



Deoxypentosenucleic Acid (DNA). Both the Feulgen nucleal reaction 1, 

 2, 41, 5G an j ultraviolet microspectrophotometry <:::i ' " 9 - s0 have established the 

 presence of DNA in the chromatin of the nuclei of the lymphocytes as well 

 as in the nuclei of other cells in the plant and animal kingdom. Morpholog- 

 ically, the nuclei of the small lymphocytes stain rather intensely and exhibit 

 a dense, coarse, Feulgen-positive chromatin pattern, while the more im- 

 mature lymphocytes and lymphoblasts possess a more delicate chromatin 

 pattern and stain less intensely than the small mature lymphocytes. 1 Fre- 

 quently, the Feulgen-positive "nucleolar associated chromatin" is very ap- 

 parent surrounding the Feulgen-negative nucleoli of the lymphoid cells. The 

 nuclei of the lymphocytes in chronic lymphocytic leukemia have a coarse, 

 darkly stained chromatin in contrast to the lymphocytes in lymphosarcoma 

 which usually stain lighter and have a more uniform distribution of 

 chromatin. 1 The enzyme desoxyribonuclease will selectively remove the 

 stainability of the lymphocyte with basic dyes 50 ' 98 or with the nucleal re- 

 action. 9 



