Radiation Effects on Lymphocytes 131 



After total body irradiation of rabbits with 100 r, many lymph follicles 

 persist more or less intact. Alter 600 r, the lymph follicles completely dis- 

 appear. De Bruyn emphasizes the differences in the reactions following low- 

 dosages of 400 r or less as compared with high dosages of 600 and 800 r. 11 

 The destruction of lymph follicles may represent only an intensification of 

 the process of lymphocytic degeneration, or perhaps it represents a new. 

 qualitatively different effect produced by high doses of x-rays. 



In spite of the rapid death of the Lymphocytes, the reticular cells in 

 Lymphoid tissue are resistant to large doses of x-rays, 61 even though the 

 reticular cells are believed to be the precursors of lymphocytes. Similarly, 

 some undifferentiated cells in the testis and ovary are more resistant to 

 x-rays than the daughter cells. The cells of the lymphocytic series are not 

 unique in being exceptions to the law of Bergonie and Tribondeau that un- 

 differentiated cells are radiosensitive. 



During the period of degenerative changes, mitoses are absent or greatly 

 reduced in the Lymphoid tissue. 27 In one study the number of mitotic 

 figures decreased from 100 to 58 per unit volume of lymph node in one 

 hour after irradiation of mice with 35 r. 23 



In the spleen of patients. Lymphocytes showed karyorrhexis and cessation 

 of mitosis, 24 to 48 hours after irradiation."' The cells undergoing karyor- 

 rhexis after a single depth close of over 400 r were apparently few/er than 

 in Lower animals, possibly due to a slower rate of destruction of the human 

 lymphocytes. The reticular cells were resistant to the treatment. In lymphoid 

 tissue the follicles were partly destroyed three to four weeks after irradiation 

 of cancer of the cervix. 57 



Autopsies of Japanese men and women who died from irradiation during 

 the first 14 days after the atomic bomb attack showed a complete or almost 

 complete absence of lymphocytes and of lymph follicles. 31 The Malpighian 

 bodies of the spleen were only vaguely outlined by whorled structures of 

 collagenous and reticular tissue. Phagocytosis of nuclear debris was seldom 

 observed although erythrophagocytosis was present in the spleens. The 

 reticular cells were resistant to a dose of irradiation that was lethal to the 

 individual. Similar findings were obtained in a man who died 10 days after 

 an accidental exposure to about 880 r x-rays. 111 In general, the early 

 changes observed in lymph nodes of human subjects after lethal total body 

 irradiation were similar to those observed in irradiated animals. 



The quantitative reaction of lymphoid tissue to x-rays in vivo has been 

 studied only by a few investigators. Trowell counted the number of necrotic 

 cells in lymph nodes of rats and obtained time-effect and dose-effect curves. 59 

 The dose-effect curves were linear on probit paper when the dosages Avere 

 35 to 630 r. Biagini obtained similar curves and in addition observed that a 

 second x-ray treatment produced the same quantitative effect as the first. 4 



