16 The Lymphocyte and Lymphocytic Tissue 



lin. 48 I have come to wonder if the cells common to peripheral plasmacel- 

 lular reactions and comparable to those that cause the confusion by virtue 

 of their presence in germinal centers may not be different from the plasma 

 cells that are so clearly perivascular in the marrow and other organs. 



The transition of large hematopoietic reticular cells to reticular lympho- 

 cytes to lymphocytes is clearly evident in lymph node imprints from infec- 

 tious mononucleosis and chronic lymphatic leukemia. 8 In these cases the 

 transitional forms resemble those of hyperplastic nonleukemic nodes, but the 

 leukocytoid lymphocytes of Downey 49 are, of course, more prominent in the 

 nodes from infectious mononucleosis. 



In the acute and subacute lymphatic leukemias, the transitional forms 

 appear to progress from narrow-bodied reticular cells to lymphoblasts to 

 immature lymphocytes to lymphocytes. 1, 8 - 50 (See Figs. 1-13, 1-14.*) The 

 lymphoblast of acute lymphatic leukemia is remarkably similar to the myelo- 

 blast of acute myelogenous leukemia, and this type of cell is uncommon in 

 normal human lymph nodes. Downey felt the lymphoblast was an abnormal 

 cell type possibly peculiar to leukemia, representing a cell form resulting, in 

 part at least, from numerous mitoses and lack of subsequent differentiation. 

 The immature lymphocyte, in contrast, is commonly present in normal lymph 

 nodes, and its presence in the marrow 1 has caused me to wonder if it may not 

 represent a transitional form from lymphocyte to myeloblast, thus providing 

 a source of myeloblasts. Yoffey's enthusiasm for this cell type 26 ' 51 - 52 has been 

 most stimulating, and we have compared our marrow specimens as well as 

 our opinions. 



With regard to the immature lymphocytes and lymphoblasts, several other 

 interesting observations seem pertinent here. Immature lymphocytes seem 

 much more numerous in imprints of the human thymus than in imprints of 

 human lymph nodes. 53 Cells resembling the lymphoblasts of acute leukemia 

 are present. 53 Immature granulocytes similar in morphology to those of the 

 marrow are present. 53, r ' 4 In addition, reticular phagocytes showing features 

 comparable to those shown in Figure 1-3 and occasional large rounded retic- 

 ular cells are present.. 53 Plasma cells are also found. 53 The presence of color- 

 less to pale-pink granules in the perinuclear cytoplasm of the immature 

 lymphocytes and lymphoblasts of the thymus makes them appear remarkably 

 similar to the immature lymphocytes and lymphoblasts of leukemia. 53 



Another interesting observation regarding immature lymphocytes involves 

 two cases of typical chronic myelogenous leukemia (of long duration) which 

 in acute exacerbation gradually lost the steadily increasing number of myelo- 

 blasts to show almost complete replacement of the marrow and of the cells 

 of the circulating blood by cells which could be classified as lymphoblasts and 



* I am grateful t<> Dr. Norman Nelson ol Detroit lor the opportunity <>l having been consulted 

 in respect to this interesting case. 



