Natl. Inst. Radiol. Sci. Ann. Rept. (NRIS—10, 197°) in the table, commonclone cells in the two tissues % sf a3 ff 3 did exist in cases B-17 and Th-3. In case B-L7, one of the fishermen exposed to fallout radiation al Bikini in 1954, a clone with a ° 3 4 uf ° o x s ad karyotype of 47, XY, mart+ occurred in the bone marrow with a frequency of about 10%. In the blood cultures four of the 690 cells (0.58%) showed the karyotype of this clone. Jn case ‘Th-3, a man injected with Thorotrast in roe - G7 e ® zit e < . my e 500 and 70 of the 3,398 cells (2%) in the blood cultures showed an identical karyotype of 46, XY, Gq-?, ° e 0 1945, 21 of the 519 cells (4%) in the bone marrow ° 1000 e 1500 8 t(2p-Gpt+) 2000 Minitum VALUES OF NEUTROPHILS Fig. 10. Correlation between chromosome aberrations (Cs cellsjand minimum valucs of neutrophils. In case RT-1, a cervic cancer with hypoplastic anemia received radio-therapy, nearly 100% of the cells in the bone marrow were members of asingle clone showing a karyotype of 46, XX, t(Bpt+;Cq—) | and the derivatives, but none of the 273. cells snalyzed in the blood cultures showed this karyolype. Common Clone Cells with Structural Chramosome Aberrations in Peripheral Lymphocytes and in Bone Marrow of Irradiated Humans Takaaki Ishihara, Sei-ichi Kohno and Toshiyuki Kumatori The Ph! chromosome cine chronice granulocy Ge leukemia is known to he present in granulocytic, erylhrocvlic and mevakaryoeylic cells in bone marrow, but nol in peripheral lymphocytes which are stimulated to divide in culture responding to PEA, The evidence has led to an idea that those lymphocyles might be developed from a separate line while the former three ce!l series are derived from a common stem cell. In mice and rats, on the other hand, the presenee of multipotent lympho-hematopoictic stem cells has been suggested. As a means of approaching the problem on the derivation of lymphocytes in their relation to bone marrow cells in humans, three radiation-cx posed individuals who showed presence of distinct clones with structural chromosome abnormalities in bone marrow were studied in order lo find out whether or not clone cells common .to penpheral lymphocytes and bone marroware present. The results of the chromosome analysis both in the bone marrow and in the cultured lymphocytes of the three cases are presented in Table 2. An seen eel 5010490 The identification of cells with the same radiation-induced markers among the dividing cells in PHA-stimulated lymphocytes and in bone marrowin cases B-17 and Th-3 scems to be conclusive evidence for the presence of a lympho-hematopoictic stem cell in man yielding both lymphoid and bone marrow descendants. The present data from irradiated humans clearly demonstrated that PHA-responsive peripheral lymphocytes are the progeny of the same stem cell for bone marrow cells, but they do not explain the reason for the absence tn peripheral lymphocytes of cells with the Ph! chromosome in chronic granulocytic leukemia or of the clone cells of case RT-1, which are observed as the majonty of the cells in bone marrow. This is a serious problem to be solved in future. (Unpublished)