Approaches to Cytogenetic Assessment of the Dose due to Radiation Exposure of the Gut-Associated Lymphoid Tissue

FISH analysis of chromosomal aberrations in T-lymphocytes from peripheral blood is used to assess exposure doses. The interpretation of the results of cytogenetic studies requires special model approaches in the cases of a non-uniform distribution of beta-emitting radionuclides in the body or combined internal and external exposure. A model of exposure of T cells and their precursors in the red bone marrow was described by us earlier. This review is focused on the approaches for the assessment of doses to T-lymphocytes in gut-associated lymphoid tissues (GALT). Based on the published data, the following items were analyzed: the exposure geometry of GALT from the chyme; the distribution of circulating T-lymphocytes in the GALT; and approaches to modeling T-lymphocyte exposure in the GALT. As a result, the age-related characteristics of the residence of various subpopulations of T-cells in the lamina propria, gut epithelium, and lymphatic follicles were estimated. The proportion of circulating T-cells in the total number of T-lymphocytes in the small intestine and colon (30-35%) was evaluated. The relative amount of time that circulating T-lymphocytes spend in the small and large intestine was estimated (2.4 and 2.7%). The values obtained will be used for assessing the doses to circulating T-lymphocytes when interpreting cytogenetic data on stable chromosomal aberrations obtained by FISH.