title: Editing antigen presentation: antigen transfer between human B lymphocytes and macrophages mediated by class A scavenger receptors.
abstract: B lymphocytes can function independently as efficient APCs. However, our previous studies demonstrate that both dendritic cells and macrophages are necessary to propagate immune responses initiated by B cell APCs. This finding led us to identify a process in mice whereby Ag-specific B cells transfer Ag to other APCs. In this study, we report the ability and mechanism by which human B lymphocytes can transfer BCR-captured Ag to macrophages. The transfer of Ag involves direct contact between the two cells followed by the capture of B cell-derived membrane and/or intracellular components by the macrophage. These events are abrogated by blocking scavenger receptor A, a receptor involved in the exchange of membrane between APCs. Macrophages acquire greater amounts of Ag in the presence of specific B cells than in their absence. This mechanism allows B cells to amplify or edit the immune response to specific Ag by transferring BCR-captured Ag to other professional APCs, thereby increasing the frequency of its presentation. Ag transfer may perpetuate chronic autoimmune responses to specific self-proteins and help explain the efficacy of B cell-directed therapies in human disease.
authors.affiliation: Section of Rheumatology, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520, USA.
authors.forename: Bohdan P
authors.initials: BP
authors.lastname: Harvey
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Quan
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Rudenga
authors.forename: Robert M
authors.initials: RM
authors.lastname: Roman
authors.forename: Joe
authors.initials: J
authors.lastname: Craft
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Mamula