title: Feedback suppression of B cell colony formation by supernatants of B colony cells: role of immunoglobulin.
abstract: We have reported previously that CD5+ B cells from mature B cell colonies provide a negative feedback signal to the growth of autologous B cell colonies. Now we have observed that supernatants from mature B cell colonies also provide a negative feedback signal to the growth of autologous B cell colonies. We investigated the mechanism of this effect by growing B cell colonies physically separated by a 0.45 micron filter from T cells in millicell-CM chambers. Addition of colony supernatants to the T cell compartment reduced the number of B cell colonies by 28 +/- 6%. Colony numbers were reduced by 11 +/- 2 and 17 +/- 5% when the supernatants were added to the B cell or to both compartments, respectively. Pulsing T cells with the B cell colony supernatants before adding them to the colonies also decreased colony numbers by 33 +/- 13%. The addition of exogenous Ig classes and IgG subclasses to B cells decreased B cell colony numbers, although the effect was variable. In the presence of T cells, IgG had the greatest suppressive activity and the subclass IgG4 was most suppressive. In the absence of T cells, high concentrations of IgG almost abolished B cell colony formation. We conclude that these supernatants provide a negative feedback signal either directly to B cells, or via T cells which may be mediated at least in part by Ig.
authors.affiliation: Department of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada.
authors.forename: L A
authors.initials: LA
authors.lastname: Fernandez
authors.forename: J M
authors.initials: JM
authors.lastname: MacSween
authors.forename: G
authors.initials: G
authors.lastname: Fallows
authors.forename: D A
authors.initials: DA
authors.lastname: Robson
mesh_terms: D015703:Antigens, CD / Q000276:immunology*; D016175:B-Lymphocyte Subsets / Q000276:immunology* / Q000378:metabolism; D018956:CD5 Antigens; D003114:Colony-Forming Units Assay; D005246:Feedback; D006801:Humans; D007136:Immunoglobulins / Q000276:immunology*; D008213:Lymphocyte Activation; D011691:Puromycin / Q000494:pharmacology; D013601:T-Lymphocytes / Q000187:drug effects / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D015703:Antigens, CD; D018956:CD5 Antigens; D007136:Immunoglobulins; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha; D011691:Puromycin