title: B cells in teleost fish act as pivotal initiating APCs in priming adaptive immunity: an evolutionary perspective on the origin of the B-1 cell subset and B7 molecules.
abstract: The long-held paradigm that B cells cannot uptake nonspecific particulate Ags for the initiation of primary adaptive immunity has been challenged by the recent discovery that teleost B cells have potent phagocytic and microbicidal abilities. This discovery provides preliminary clues that primitive B cells might act as initiating APCs in priming adaptive immunity. In this study, zebrafish B cells clearly showed a potent Ag-presenting ability to both soluble Ags and bacterial particles to prime naive CD4(+) T cell activation. This finding demonstrates the innate-like nature of teleost B cells in the interface of innate and adaptive immunity, indicating that they might consist of a major population of initiating APCs whose performance is similar to that of dendritic cells. Given the functional similarities between teleost B cells and the mammalian B-1 subset, we hypothesize that B-1 lineage and teleost B cells might originate from a common ancestor with potent phagocytic and initiating APC capacities. In addition, CD80/86 and CD83 costimulatory signals were identified as being essential for B cell-initiated adaptive immunity. This result suggests that the costimulatory mechanism originated as early as the origin of adaptive immunity and is conserved throughout vertebrate evolution. In fish, only a single CD80/86 copy exists, which is similar to mammalian CD86 rather than to CD80. Thus, CD86 might be a more primordial B7 family member that originated from fish. This study provides valuable insights into the evolutionary history of professional APCs, B cell lineages, and the costimulatory mechanism underlying adaptive immunity as a whole.
authors.affiliation: College of Life Sciences, Zhejiang University, Hangzhou 310058, People's Republic of China;
authors.forename: Lv-yun
authors.initials: LY
authors.lastname: Zhu
authors.forename: Ai-fu
authors.initials: AF
authors.lastname: Lin
authors.forename: Tong
authors.initials: T
authors.lastname: Shao
authors.forename: Li
authors.initials: L
authors.lastname: Nie
authors.forename: Wei-ren
authors.initials: WR
authors.lastname: Dong
authors.forename: Li-xin
authors.initials: LX
authors.lastname: Xiang
authors.forename: Jian-zhong
authors.initials: JZ
authors.lastname: Shao
mesh_terms: D056704:Adaptive Immunity / Q000235:genetics / Q000276:immunology*; D000595:Amino Acid Sequence; D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology* / Q000378:metabolism; D015703:Antigens, CD / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D016175:B-Lymphocyte Subsets / Q000276:immunology* / Q000378:metabolism; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D060887:B7 Antigens / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D018122:B7-1 Antigen / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D051940:B7-2 Antigen / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D001483:Base Sequence; D015153:Blotting, Western; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D019143:Evolution, Molecular; D005260:Female; D020869:Gene Expression Profiling; D007136:Immunoglobulins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D044149:Vibrio alginolyticus / Q000276:immunology; D015027:Zebrafish / Q000235:genetics / Q000276:immunology*; D029961:Zebrafish Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D000097802:CD83 Antigen
chemical_list: D015703:Antigens, CD; D060887:B7 Antigens; D018122:B7-1 Antigen; D051940:B7-2 Antigen; D007136:Immunoglobulins; D008562:Membrane Glycoproteins; D029961:Zebrafish Proteins; D000097802:CD83 Antigen