title: The expression of Bcl-2 family proteins (Bcl-2, Bcl-x, Bax, Bak and Bim) in human lymphocytes.
abstract: Bcl-2 family proteins regulate programmed cell death, and may play an important role in the selection of lymphocytes. We investigated the expression of Bcl-2, Bcl-x, Bax, Bak and Bim in human lymphocytes using flow-cytometry. Bcl-2 was down-regulated in CD4(+)8(+) (DP) thymocytes and CD19(+)38(+) tonsillar lymphocytes (GC B cells). Among DP thymocytes, cells co-expressing CD69 up-regulated Bcl-2, suggesting that the role of Bcl-2 is promoting survival of positively selected DP cells. Unexpectedly, the expression level of Bcl-x was higher in DP cells than in Single Positive (SP) cells and in CD69(+) DP thymocytes it was lower than in CD69(+) DP thymocytes. Expression of Bim was low in DP thymocytes but high in a subset of GC B cells. Bim and Bax were expressed more highly in SP than in DP thymocytes. Among peripheral blood lymphocytes (PBL), CD8(+) T cells expressed an approximately ten-fold higher level of Bcl-x than CD4(+) T cells while both subsets expressed similar levels of Bcl-2. Bak expression was low and Bim expression was absent in PBL. These results suggest that not only Bcl-2 but other members of the Bcl-2 family are involved in T cell development in the thymus and affinity maturation of B cells in the germinal center.
authors.affiliation: Department of Surgery II, Nagoya City University, Medical School, Kawasumi 1, Mizuho-ku, Nagoya 467-8601, Japan.
authors.forename: Tomoki
authors.initials: T
authors.lastname: Yokoyama
authors.forename: Masayuki
authors.initials: M
authors.lastname: Tanahashi
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Yamakawa
authors.forename: Masanobu
authors.initials: M
authors.lastname: Maeda
authors.forename: Toshiya
authors.initials: T
authors.lastname: Inaba
authors.forename: Masanobu
authors.initials: M
authors.lastname: Kiriyama
authors.forename: Ichiro
authors.initials: I
authors.lastname: Fukai
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Fujii
mesh_terms: D000328:Adult; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D001402:B-Lymphocytes / Q000378:metabolism*; D000072224:Bcl-2-Like Protein 11; D002352:Carrier Proteins / Q000096:biosynthesis*; D018858:Germinal Center / Q000166:cytology; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000378:metabolism; D008565:Membrane Proteins / Q000096:biosynthesis*; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis*; D013601:T-Lymphocytes / Q000378:metabolism*; D013950:Thymus Gland / Q000166:cytology; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
chemical_list: D051017:Apoptosis Regulatory Proteins; C494772:BAK1 protein, human; C494826:BAX protein, human; C494811:BCL2L1 protein, human; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; D002352:Carrier Proteins; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein