title: Selective preservation of bone marrow mature recirculating but not marginal zone B cells in murine models of chronic inflammation.
abstract: Inflammation promotes granulopoiesis over B lymphopoiesis in the bone marrow (BM). We studied B cell homeostasis in two murine models of T cell mediated chronic inflammation, namely calreticulin-deficient fetal liver chimeras (FLC), which develop severe blepharitis and alopecia due to T cell hyper responsiveness, and inflammatory bowel disease (IBD) caused by injection of CD4(+) naïve T cells into lymphopenic mice. We show herein that despite the severe depletion of B cell progenitors during chronic, peripheral T cell-mediated inflammation, the population of BM mature recirculating B cells is unaffected. These B cells are poised to differentiate to plasma cells in response to blood borne pathogens, in an analogous fashion to non-recirculating marginal zone (MZ) B cells in the spleen. MZ B cells nevertheless differentiate more efficiently to plasma cells upon polyclonal stimulation by Toll-like receptor (TLR) ligands, and are depleted during chronic T cell mediated inflammation in vivo. The preservation of mature B cells in the BM is associated with increased concentration of macrophage migration inhibitory factor (MIF) in serum and BM plasma. MIF produced by perivascular dendritic cells (DC) in the BM provides a crucial survival signal for recirculating B cells, and mice treated with a MIF inhibitor during inflammation showed significantly reduced mature B cells in the BM. These data indicate that MIF secretion by perivascular DC may promote the survival of the recirculating B cell pool to ensure responsiveness to blood borne microbes despite loss of the MZ B cell pool that accompanies depressed lymphopoiesis during inflammation.
authors.affiliation: Istituto Giannina Gaslini, Genoa, Italy. elisabetta.traggiai@gmail.com
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Traggiai
authors.forename: Anna
authors.initials: A
authors.lastname: Casati
authors.forename: Michela
authors.initials: M
authors.lastname: Frascoli
authors.forename: Simona
authors.initials: S
authors.lastname: Porcellini
authors.forename: Maurilio
authors.initials: M
authors.lastname: Ponzoni
authors.forename: Francesca
authors.initials: F
authors.lastname: Sanvito
authors.forename: Lin
authors.initials: L
authors.lastname: Leng
authors.forename: Richard
authors.initials: R
authors.lastname: Bucala
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Moretta
authors.forename: Fabio
authors.initials: F
authors.lastname: Grassi
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology*; D001854:Bone Marrow Cells / Q000166:cytology*; D002908:Chronic Disease; D015925:Cryopreservation; D004195:Disease Models, Animal; D005786:Gene Expression Regulation; D007249:Inflammation / Q000473:pathology*; D051379:Mice; D014158:Transcription, Genetic