Genetic background and lymphocyte populations after total-body exposure to iron ion radiation.
OBJECTIVE
Particle radiations could significantly impact astronaut health during space missions. This study quantified the effects of iron ion radiation on lymphocytes in two strains of mice differing in susceptibility to radiation-induced acute myeloid leukemia (AML) and thymic lymphoma (TL): C57BL/6 (AML resistant, TL sensitive) and CBA/Ca (AML sensitive, TL resistant).


METHODS
The animals (n = 60/strain) were irradiated with ⁵⁶Fe(26+) (1 GeV) to total doses of 0, 0.5, 2 and 3 Gray (Gy) at an average dose rate of 1 Gy/min and euthanised on days 4 and 30 thereafter; blood, spleen, and bone marrow were collected for flow cytometry analyses. Cells expressing the following molecules were quantified: Cluster of differentiation (CD) 4, CD8, CD25, CD34, CD71, B220 (isoform of CD45 on B cells), NK1.1 (marker on natural killer or NK cells, C57B mice), panNK (marker on NK cells, CBA mice), and Sca1 (stem cell antigen 1).


RESULTS
Exposure to radiation resulted in different distribution patterns in lymphocyte populations and leukocytes expressing activation and progenitor markers in the two mouse strains. Significant main effects were dependent upon strain, as well as radiation dose, body compartment, and time of assessment. Especially striking differences were noted on day 4 after 3 Gy irradiation, including in the CD4:CD8 ratio [blood, C57 (2.83 ± 0.25) vs. CBA (6.19 ± 0.24); spleen, C57 (2.29 ± 0.12) vs. CBA (4.98 ± 0.22)], %CD25(+) mononuclear cells in bone marrow [C57 (5.62 ± 1.19) vs. CBA (12.45 ± 0.93)] and %CD34(+)Sca1(+) cells in bone marrow [CD45¹° gate, C57 (2.72 ± 0.74) vs. CBA (21.44 ± 0.73)].


CONCLUSIONS
The results show that genetic background, as well as radiation dose and time post-exposure, had a profound impact on lymphocyte populations, as well as other leukocytes, after exposure to iron ion radiation.
Department of Radiation Medicine, Radiation Research Laboratories, Divisions of Microbiology & Biochemistry, Loma Linda University and Medical Center, Loma Linda, California 92354, USA. dgridley@dominion.llumc.edu
Daila S
DS
Gridley
Michael J
MJ
Pecaut
D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D001854:Bone Marrow Cells / Q000276:immunology / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D005434:Flow Cytometry; D006801:Humans; D053645:Interleukin-2 Receptor alpha Subunit / Q000378:metabolism; D007504:Iron Radioisotopes / Q000009:adverse effects*; D008213:Lymphocyte Activation; D016131:Lymphocyte Subsets / Q000276:immunology / Q000528:radiation effects*; D054503:Lymphoid Progenitor Cells / Q000276:immunology / Q000528:radiation effects; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D023421:Models, Animal; D011836:Radiation Tolerance / Q000235:genetics / Q000276:immunology; D011990:Receptors, Transferrin / Q000378:metabolism; D013026:Space Flight; D013045:Species Specificity; D013154:Spleen / Q000166:cytology / Q000276:immunology / Q000528:radiation effects; D014916:Whole-Body Irradiation / Q000009:adverse effects*
D015703:Antigens, CD; C068126:CD71 antigen; C508018:Il2ra protein, mouse; D053645:Interleukin-2 Receptor alpha Subunit; D007504:Iron Radioisotopes; D011990:Receptors, Transferrin