title: Dose and dose rate effects of whole-body proton irradiation on leukocyte populations and lymphoid organs: part I.
abstract: The goal of part I of this study was to evaluate the effects of whole-body proton irradiation on lymphoid organs and specific leukocyte populations. C57BL/6 mice were exposed to the entry region of the proton Bragg curve to total doses of 0.5 gray (Gy), 1.5 Gy, and 3.0 Gy, each delivered at a low dose rate (LDR) of 1 cGy/min and high dose rate (HDR) of 80 cGy/min. Non-irradiated and 3 Gy HDR gamma-irradiated groups were included as controls. At 4 days post-irradiation, highly significant radiation dose-dependent reductions were observed in the mass of both lymphoid organs and the numbers of leukocytes and T (CD3(+)), T helper (CD3(+)/CD4(+)), T cytotoxic (CD3(+)/CD8(+)), and B (CD19(+)) cells in both blood and spleen. A less pronounced dose effect was noted for natural killer (NK1.1(+) NK) cells in spleen. Monocyte, but not granulocyte, counts in blood were highly dose-dependent. The numbers for each population generally tended to be lower with HDR than with LDR radiation; a significant dose rate effect was found in the percentages of T and B cells, monocytes, and granulocytes and in CD4(+):CD8(+) ratios. These data indicate that mononuclear cell response to the entry region of the proton Bragg curve is highly dependent upon the total dose and that dose rate effects are evident with some cell types. Results from gamma- and proton-irradiated groups (both at 3 Gy HDR) were similar, although proton-irradiation gave consistently lower values in some measurements.
authors.affiliation: Department of Radiation Medicine, Radiobiology Program, Loma Linda University School of Medicine and Medical Center, Chan Shun Pavilion, Room A-1010, 11175 Campus Street, Loma Linda, CA 92354, USA. dgridley@dominion.llumc.edu
authors.forename: Daila S
authors.initials: DS
authors.lastname: Gridley
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Pecaut
authors.forename: Radha
authors.initials: R
authors.lastname: Dutta-Roy
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Nelson
mesh_terms: D000818:Animals; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005434:Flow Cytometry; D006098:Granulocytes / Q000528:radiation effects; D007958:Leukocyte Count; D007962:Leukocytes / Q000528:radiation effects*; D016131:Lymphocyte Subsets / Q000528:radiation effects; D051379:Mice; D008810:Mice, Inbred C57BL; D011522:Protons / Q000009:adverse effects*; D013154:Spleen / Q000166:cytology / Q000528:radiation effects*; D013950:Thymus Gland / Q000166:cytology / Q000528:radiation effects*; D014916:Whole-Body Irradiation / Q000009:adverse effects*
chemical_list: D011522:Protons