title: Homeostatic 'bystander' proliferation of human peripheral blood B cells in response to polyclonal T-cell stimulation in vitro.
abstract: The mechanisms of maintenance of adequate numbers of B lymphocytes and of protective levels of immunoglobulins in the absence of antigenic (re)stimulation remain not fully understood. Meanwhile, our results presented here show that both peripheral blood naive and memory B cells can be activated strongly and non-specifically (in a mitogen-like fashion) in 5-day in vitro cultures of anti-CD3- or concanavalin A (Con A)-stimulated peripheral blood mononuclear cells of healthy people. This polyclonal, bystander activation of the B cells includes multiple divisions of most of them (assessed here by the flow cytometric technique of dividing cell tracking) and significant antibody [immunoglobulin M (IgM) and IgG] secretion. Observed proliferation of the CD19(+) B cells depends on contact with stimulated T helper (Th) cells (via CD40-CD40L interaction) and on the response of B cells to secreted interleukins IL-5, IL-10 and IL-4, and is correlated with the levels of these Th-derived molecules, while it does not involve the ligation of the BCR/CD19 complex. We suggest that the effect might reflect the situation occurring in vivo as the homeostatic proliferation of otherwise non-stimulated, peripheral B lymphocytes, providing an always ready pool for efficient antibody production to any new (or cognate) antigen challenge.
authors.affiliation: Department of Pathophysiology, Medical University of Gdańsk, Dębinki 7, 80-211 Gdańsk, Poland.
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Jasiulewicz
authors.affiliation: Department of Pathophysiology, Medical University of Gdańsk, Dębinki 7, 80-211 Gdańsk, Poland.
authors.forename: Katarzyna A
authors.initials: KA
authors.lastname: Lisowska
authors.affiliation: Department of Pathophysiology, Medical University of Gdańsk, Dębinki 7, 80-211 Gdańsk, Poland.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Pietruczuk
authors.affiliation: Department of Pathophysiology, Medical University of Gdańsk, Dębinki 7, 80-211 Gdańsk, Poland.
authors.forename: Joanna
authors.initials: J
authors.lastname: Frąckowiak
authors.affiliation: Research Center on Aging, Department of Medicine, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, Quebec, Canada.
authors.forename: Tamas
authors.initials: T
authors.lastname: Fulop
authors.affiliation: Department of Pathophysiology, Medical University of Gdańsk, Dębinki 7, 80-211 Gdańsk, Poland jawit@gumed.edu.pl.
authors.forename: Jacek M
authors.initials: JM
authors.lastname: Witkowski
mesh_terms: D000328:Adult; D000368:Aged; D000917:Antibody Formation / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D002450:Cell Communication / Q000276:immunology*; D002453:Cell Cycle; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000096:biosynthesis; D007075:Immunoglobulin M / Q000096:biosynthesis; D007963:Leukocytes, Mononuclear / Q000276:immunology / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology*; D008212:Lymphocyte Depletion; D008297:Male; D008875:Middle Aged; D016176:T-Lymphocyte Subsets / Q000276:immunology* / Q000378:metabolism
chemical_list: D016207:Cytokines; D007074:Immunoglobulin G; D007075:Immunoglobulin M
keywords: B cells; B/T cell cooperation; T cells; healthy; homeostatic proliferation; human PBMC; in vitro