CHAPTER 10 



RADIATION EFFECTS ON 

 LYMPHOCYTES 



ROBERT SCHREK 



The lymphocyte is a unique cell. It is the only nonmitotic cell that is sensi- 

 tive to small doses of x-rays. In contrast, the granulocyte is highly radio- 

 resistant. In this paper I shall consider not only the biologic reactions of 

 lymphoid tissue to x-rays but also the use of x-rays as a tool to study the 

 physiology of the lymphocyte. I shall first review the in vitro findings as these 

 have clarified the in vivo observations. 



IN VITRO STUDIES 



The morphologic effects of x-rays on lymphocytes in vitro have been 

 studied by time-lapse cinemicrography. 49 Three hours after in vitro irradia- 

 tion of rabbit lymphocytes with 1000 r. most of the cells still appear morpho- 

 logically normal (Fig. 10-1). The photomicrographs were taken with phase 

 contrast microscopy and show clearly the nucleus and cytoplasm, the nuclear 

 wall, and the chromatin masses in the living unstained lymphocyte. The first 

 degenerative change in the irradiated cell is the appearance of a small intra- 

 nuclear vacuole (Fig. 10-2). Shortly after the onset of the vacuole, the cell 

 and the nucleus usually start to change shape rapidly with the formation of 

 lobulations (Fig. 10-3). Frequently each lobule has a separate fragment of 

 nucleus as is seen in cell F in Figure 10-3 and still more clearly in Figure 

 10-4 where the cell seems divided into two separate parts, each with a vacu- 

 olated nucleus. The vacuoles continue to grow, pushing the chromatin pe- 

 ripherally to form a ring or a sphere of chromatin. In about 20 minutes 

 after onset, the vacuole ruptures the chromatin ring as is seen in cell C, 

 Figure 10-5, and the chromatin appears horseshoe-shaped. The degenerated 

 chromatin material is apparently fluid and contracts to form a crescent, a 



125 



