title: Memory CD4 T-cell subsets discriminated by CD43 expression level in A-bomb survivors.
abstract: OBJECTIVE
  Our previous study showed that radiation exposure reduced the diversity of repertoires of memory thymus-derived cells (T cells) with cluster of differentiation (CD)- 4 among atomic-bomb (A-bomb) survivors. To evaluate the maintenance of T-cell memory within A-bomb survivors 60 years after radiation exposure, we examined functionally distinct memory CD4 T-cell subsets in the peripheral blood lymphocytes of the survivors.
  
  
  METHODS
  Three functionally different subsets of memory CD4 T cells were identified by differential CD43 expression levels and measured using flow cytometry. These subsets consist of functionally mature memory cells, cells weakly responsive to antigenic stimulation, and those cells functionally anergic and prone to spontaneous apoptosis.
  
  
  RESULTS
  The percentages of these subsets within the peripheral blood CD4 T-cell pool all significantly increased with age. Percentages of functionally weak and anergic subsets were also found to increase with radiation dose, fitting to a log linear model. Within the memory CD4 T-cell pool, however, there was an inverse association between radiation dose and the percentage of functionally mature memory cells.
  
  
  CONCLUSIONS
  These results suggest that the steady state of T cell memory, which is regulated by cell activation and/or cell survival processes in subsets, may have been perturbed by prior radiation exposure among A-bomb survivors.
authors.affiliation: Department of Radiobiology, Yasuda Women's University, Hiroshima, Japan.
authors.forename: Seishi
authors.initials: S
authors.lastname: Kyoizumi
authors.forename: Mika
authors.initials: M
authors.lastname: Yamaoka
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Kubo
authors.forename: Kanya
authors.initials: K
authors.lastname: Hamasaki
authors.forename: Tomonori
authors.initials: T
authors.lastname: Hayashi
authors.forename: Kei
authors.initials: K
authors.lastname: Nakachi
authors.forename: Fumiyoshi
authors.initials: F
authors.lastname: Kasagi
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Kusunoki
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000528:radiation effects*; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007156:Immunologic Memory / Q000528:radiation effects*; D017493:Leukocyte Common Antigens / Q000032:analysis; D051917:Leukosialin / Q000032:analysis / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009689:Nuclear Warfare; D017741:Survivors
chemical_list: D051917:Leukosialin; C465014:SPN protein, human; D017493:Leukocyte Common Antigens