title: Stimulated rapid expression in vitro for early detection of in vivo T-cell receptor mutations induced by radiation exposure.
abstract: The T-cell receptor (TCR) mutation assay for in vivo somatic mutations is a sensitive indicator of exposure to ionizing radiation. However, this assay cannot be immediately applied after radiation exposure because expression of a mutant phenotype may require as long as several months. In the present study, we eliminate this time lag by stimulating lymphocytes with a mitogen that can accelerate the turnover of TCR protein expression in T-cells. When lymphocytes obtained from healthy donors were irradiated with various doses of X-rays and cultured with human interleukin-2 after phytohemagglutinin (PHA) pulse stimulation, the mutant frequency (MF) of CD4+ T-cells increased dose dependently during the first 7 days, then decreased rapidly due to the growth disadvantage of mutant cells. This suggests that PHA stimulation can shorten the expression time of a mutant phenotype to within a week after radiation exposure. The relationship between radiation dose and TCR MF on the seventh day was best fitted by a linear-quadratic dose-response model. We applied this improved TCR mutation assay to gynecological cancer patients who received 5 days of localized radiotherapy, totaling about 10 Gy. The in vivo TCR MF in the patients did not change within a week after radiotherapy, whereas the in vitro TCR MF of PHA-stimulated lymphocytes from the same patients significantly increased 7 days after initiating culture. The estimated mean radiation dose to the peripheral blood lymphocytes of the cancer patients was about 0.9 Gy, based on the in vitro linear-quadratic dose-response curve. This estimated dose was close to that described in a previous report on unstable-type chromosome aberrations from cervical cancer patients after receiving the same course of radiotherapy. On the basis of these findings, we propose that the improved TCR mutation assay is a useful biological dosimeter for recent radiation exposure.
authors.affiliation: Department of Radiobiology, Hiroshima, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Ishioka
authors.forename: S
authors.initials: S
authors.lastname: Umeki
authors.forename: Y
authors.initials: Y
authors.lastname: Hirai
authors.forename: M
authors.initials: M
authors.lastname: Akiyama
authors.forename: T
authors.initials: T
authors.lastname: Kodama
authors.forename: K
authors.initials: K
authors.lastname: Ohama
authors.forename: S
authors.initials: S
authors.lastname: Kyoizumi
mesh_terms: D000945:Antigens, Differentiation, T-Lymphocyte / Q000096:biosynthesis* / Q000235:genetics; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism / Q000528:radiation effects*; D002455:Cell Division / Q000528:radiation effects; D002478:Cells, Cultured; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005434:Flow Cytometry; D015870:Gene Expression; D006801:Humans; D007376:Interleukin-2 / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects / Q000528:radiation effects; D008297:Male; D016296:Mutagenesis / Q000528:radiation effects; D009154:Mutation; D010835:Phytohemagglutinins / Q000494:pharmacology; D011879:Radiotherapy Dosage; D011948:Receptors, Antigen, T-Cell / Q000235:genetics* / Q000528:radiation effects; D002583:Uterine Cervical Neoplasms / Q000532:radiotherapy
chemical_list: D000945:Antigens, Differentiation, T-Lymphocyte; D007376:Interleukin-2; D010835:Phytohemagglutinins; D011948:Receptors, Antigen, T-Cell