Radiation Effects on Lymphocytes 133 



Most workers report that 25 r are the minimum total body dose required 

 to produce an appreciable decrease of lymphocytes in individual animals. 21 

 In rabbits, for example, 25 r produced a decrease of about 25 per cent in 

 the lymphocyte count in 24 hours. A statistically significant reduction of 

 lymphocytes followed irradiation of groups of mice with 10 r according 

 to Dougherty and White 14 and of rats with 5 r according to Ingram and 

 Mason. 19 



6000 



RABBIT 



MAN 



FT 



180 r 



DAYS AFTER IRRADIATION 



Fig. 10-8. Early effects of total body irradiation on the number of lympho- 

 cytes in the blood. (Data on rabbits from Sacher and Pearlman 10 and on 

 man from Hemplemann, Lisco, and Hoffman. 16 ) 



In four patients treated with a total body exposure of 60 r, the lympho- 

 cyte count dropped in one day to 31 to 61 per cent of the original 

 count. 40 One patient treated with 27 r and three normal individuals treated 

 with 3 daily doses of 7 r did not develop any appreciable decrease in lympho- 

 cyte count. A significant lymphopenia developed in patients who received 

 total body irradiation of two daily doses of 20 r each. 32 The degree of 

 lymphopenia after irradiation with varying dosages of x-rays was of the 

 same order of magnitude in man, rat, and rabbit (Fig. 10-9). 



According to Cronkite's summary, an acute total body exposure of 25 r 

 usually produces no definite lymphopenia in man, of 100 r results in a 

 mild lymphopenia, and of over 100 r causes a lymphocyte count as low as 

 10 per cent of the normal in 24 hours. 9 



