title: B-1 cells: unique origins and functions.
abstract: B-1 cells represent a distinct population of B lymphocytes with unique phenotypic, developmental and functional characteristics. We present evidence that the expression of MHC class II antigens differentiates two distinct developmental pathways which define the fetal-type (FT) and adult-type B-cell lineages. Further in-vivo and in-vitro analyses suggest that B-1 cells are derived primarily if not exclusively from the FT lineage. Combining these results with other studies suggesting that signalling plays a role in the development of B-1 cells, we propose a modified dual lineage model for the generation of B-1 cells. In this model fetal-type B cells are uniquely 'born' with the capacity to be B-1 cells, however, they must be properly educated (i.e. receive the appropriate signals) before they can be 'made' functional, phenotypic B-1 cells. With respect to the function of B-1 cells, we have used PerC/BM allotype chimeric animals to investigate the capacity of B-1 cells to participate in the formation of germinal centers. In these mice we were unable to detect any significant involvement of B-1 cells in the generation of germinal centers. These results are discussed in the context of the known characteristics of B-1 responses including the low frequency of hypermutation and isotype class switching.
authors.affiliation: Department of Microbiology, Columbia University, New York, NY 10032, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Stall
authors.forename: S M
authors.initials: SM
authors.lastname: Wells
authors.forename: K P
authors.initials: KP
authors.lastname: Lam
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology / Q000502:physiology*; D018956:CD5 Antigens / Q000032:analysis*; D000949:Histocompatibility Antigens Class II / Q000032:analysis; D006801:Humans; D007107:Immune System / Q000502:physiology; D008213:Lymphocyte Activation
chemical_list: D018956:CD5 Antigens; D000949:Histocompatibility Antigens Class II