Risks and Modeling at Low Doses

Sunday, October 16, 2005 3:00 PM-5:00 PM Exhibit Hall

(PP054) CD4+ and CD8+ T-cell responses to ionizing radiation.

Mullins, Dana1, Prud'homme-Lalonde, Louise1, Qutob, Sami2, Lachapelle, Sylvie1, Segura, Tamika1, Thorleifson, Erika2, Wilkinson, Diana*,1, 1 Department of National Defence, Ottawa, Ontario, Canada2 Health Canada, Ottawa, Ontario, Canada

ABSTRACT- When an overexposure to ionizing radiation occurs within the military or public environment, it is essential to rapidly identify exposed individuals for immediate medical attention and long-term health risk surveillance. Existing cytogenetic methods have limitations in sensitivity, available expertise and expedience of use. Development of new rapid diagnostic methodologies that can be conducted by any clinical laboratory would greatly enhance detection and identification capacity. Peripheral blood lymphocytes are an ideal biological material for monitoring radiation exposures since these cells are most vulnerable and easily attainable. The biological consequence of the acquired cellular damage above 1 Gy is traditionally evaluated by following the rate of white blood cell depletion over a 48-hour period after exposure. A clinically significant hematopoietic syndrome occurs as a result of bone marrow depression after a whole body irradiation dose of about 2 Gy or higher. There is evidence in the literature to suggest that CD4+ and CD8+ T-cells, as representative subpopulations of the hematopoietic system, are particularly sensitive to ionizing radiation. We will present data from analytical cytometry studies using Personal Cell Analysis (PCA) to screen irradiated blood samples following ex vivo and in vivo exposures to radiation and compare CD4+ and CD8+ T-cells counts and ratios to the pre-determined baseline levels in un-irradiated individuals. This information may lead to rapid analysis of time course profiling of sensitive blood cell responses and to the rapid identification of individuals that would have the highest benefit from medical interventional procedures. The added benefit of using PCA systems is that they provide a portable test platform requiring only a small (10 mL) blood sample, thus making them ideal as triage tools.

Key words: biodosimetry, lymphocytes, CD4+, CD8+

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2005 RRS