title: B cell immunopoiesis: visualizing the impact of CD40 engagement on the course of T cell-independent immune responses in an Ig transgenic system.
abstract: This study tracks the fate of antigen-reactive B cells through follicular and extrafollicular responses and addresses the function of CD40 in these processes. The unique feature of this system is the use of transgenic B cells in which the heavy chain locus has been altered by site-directed insertion of a rearranged V(H) DJ(H) exon such that they are able to clonally expand, isotype-switch and follow a normal course of differentiation upon immunization. These Ig transgenic B cells when adoptively transferred into non-transgenic (Tg) mice in measured amounts expanded and differentiated distinctively in response to T cell-independent (TI) or T cell-dependent (TD) antigens. The capacity of these Tg B cells to faithfully recapitulate the humoral immune response to TI and TD antigens provides the means to track clonal B cell behavior in vivo. Challenge with TI antigen in the presence of agonistic anti-CD40 mAb resulted in well-defined alterations of the TI response. In vivo triggering of Tg B cells with TI antigen and CD40 caused an increase in the levels IgG produced and a broadening of the Ig isotype profile, characteristics which partially mimic TD responses. Although some TD characteristics were induced by TI antigen and CD40 triggering, the Tg B cells failed to acquire a germinal center phenotype and failed to generate a memory response. Therefore, TD-like immunity can be only partially reconstituted with CD40 agonists and TI antigens, suggesting that there are additional signals required for germinal center formation and development of memory.
authors.affiliation: Department of Microbiology, Dartmouth Medical School, Lebanon, NH 03756, USA.
authors.forename: L D
authors.initials: LD
authors.lastname: Erickson
authors.forename: L A
authors.initials: LA
authors.lastname: Vogel
authors.forename: M
authors.initials: M
authors.lastname: Cascalho
authors.forename: J
authors.initials: J
authors.lastname: Wong
authors.forename: M
authors.initials: M
authors.lastname: Wabl
authors.forename: B G
authors.initials: BG
authors.lastname: Durell
authors.forename: R J
authors.initials: RJ
authors.lastname: Noelle
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D000917:Antibody Formation; D001402:B-Lymphocytes / Q000276:immunology*; D019013:CD40 Antigens / Q000276:immunology*; D005803:Genes, Immunoglobulin; D017578:Immunoglobulin Class Switching; D051379:Mice; D008822:Mice, Transgenic; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D019013:CD40 Antigens