title: Activated mast cells promote differentiation of B cells into effector cells.
abstract: Based on the known accumulation of mast cells (MCs) in B cell-dependent inflammatory diseases, including rheumatoid arthritis, we hypothesized that MCs directly modulate B cells. We show here that degranulated, and to a lesser extent naïve or IgE-sensitized, MCs activate both naïve and B cell receptor-activated B cells. This was shown by increased proliferation, blast formation, and expression of CD19, MHC class II and CD86 in the B cells. Further, MCs stimulated the secretion of IgM and IgG in IgM(+) B cells, indicating that MCs can induce class-switch recombination in B cells. We also show that coculture of MCs with B cells promotes surface expression of L-selectin, a homing receptor, on the B cells. The effects of MCs on B cells were partly dependent on cell-cell contact and both follicular and marginal zone B cells could be activated by MCs. Our findings suggest that degranulated MCs support optimal activation of B cells, a finding that is in line with in vivo studies showing that MCs frequently degranulate in the context of B-cell driven pathologies such as arthritis. Together, our findings show that MCs have the capacity to differentiate B cells to effector cells.
authors: Uppsala University, Department of Cell and Molecular Biology, Uppsala, Sweden.
authors: Anna-Karin E
authors: AK
authors: Palm
authors: Swedish University of Agricultural Sciences, Department of Anatomy, Physiology and Biochemistry, Uppsala, Sweden.
authors: Gianni
authors: G
authors: Garcia-Faroldi
authors: Uppsala University, Department of Cell and Molecular Biology, Uppsala, Sweden.
authors: Marcus
authors: M
authors: Lundberg
authors: Uppsala University, Department of Medical Biochemistry and Microbiology, Uppsala, Sweden.|Swedish University of Agricultural Sciences, Department of Anatomy, Physiology and Biochemistry, Uppsala, Sweden.
authors: Gunnar
authors: G
authors: Pejler
authors: Uppsala University, Department of Cell and Molecular Biology, Uppsala, Sweden.
authors: Sandra
authors: S
authors: Kleinau
mesh_terms: D000818:Animals; D017951:Antigen Presentation; D001402:B-Lymphocytes / Q000166:cytology* / Q000276:immunology; D002450:Cell Communication; D002454:Cell Differentiation; D049109:Cell Proliferation; D002478:Cells, Cultured; D018920:Coculture Techniques; D005260:Female; D019041:L-Selectin / Q000378:metabolism*; D008213:Lymphocyte Activation; D008297:Male; D008407:Mast Cells / Q000166:cytology*; D051379:Mice
chemical_list: C546935:SELL protein, human; D019041:L-Selectin