Ly6Chi Monocytes Provide a Link between Antibiotic-Induced Changes in Gut Microbiota and Adult Hippocampal Neurogenesis

Antibiotics, though remarkably useful, can also cause certain adverse effects. We detected that treatment of adult mice with antibiotics decreases hippocampal neurogenesis and memory retention. Reconstitution with normal gut flora (SPF) did not completely reverse the deficits in neurogenesis unless the mice also had access to a running wheel or received probiotics. In parallel to an increase in neurogenesis and memory retention, both SPF-reconstituted mice that ran and mice supplemented with probiotics exhibited higher numbers of Ly6Chi monocytes in the brain than antibiotic-treated mice. Elimination of Ly6Chi monocytes by antibody depletion or the use of knockout mice resulted in decreased neurogenesis, whereas adoptive transfer of Ly6Chi monocytes rescued neurogenesis after antibiotic treatment. We propose that the rescue of neurogenesis and behavior deficits in antibiotic-treated mice by exercise and probiotics is partially mediated by Ly6Chi monocytes

High levels of SOX5 decrease proliferative capacity of human B cells, but permit plasmablast differentiation.

Currently very little is known about the differential expression and function of the transcription factor SOX5 during B cell maturation. We identified two new splice variants of SOX5 in human B cells, encoding the known L-SOX5B isoform and a new shorter isoform L-SOX5F. The SOX5 transcripts are highly expressed during late stages of B-cell differentiation, including atypical memory B cells, activated CD21low B cells and germinal center B cells of tonsils. In tonsillar sections SOX5 expression was predominantly polarized to centrocytes within the light zone. After in vitro stimulation, SOX5 expression was down-regulated during proliferation while high expression levels were permissible for plasmablast differentiation. Overexpression of L-SOX5F in human primary B lymphocytes resulted in reduced proliferation, less survival of CD138neg B cells, but comparable numbers of CD138+CD38hi plasmablasts compared to control cells. Thus, our findings describe for the first time a functional role of SOX5 during late B cell development reducing the proliferative capacity and thus potentially affecting the differentiation of B cells during the germinal center response

SOX5 modulates <i>in vitro</i> terminal B cell differentiation.

<p>(A) Proliferation measured as the ratio of absolute numbers of GFP⁺ cells in the samples. Absolute cell counts of GFP⁺ cells on day 0 are taken as 1.0 and the data are expressed as mean ± SD. Summary of three independent experiments are depicted. (B) Frequencies of GFP⁺ DAPI⁺ cells within GFP (control) and SOX5-GFP-transduced peripheral blood B cells cultivated <i>in vitro</i>. (C) Plasma cell differentiation analyzed by FACS in peripheral blood B cells stably transduced either with GFP (control) or SOX5-GFP fusion construct upon <i>in vitro</i> stimulation with IL4+CD40L+IL21. DAPI-negative GFP⁺ gated cells were analyzed by FACS for the plasma cell markers CD138 and CD38 at days 3, 6 and 9. Gates indicate the frequencies of CD138⁺CD38^hi plasmablasts in each FACS plot. Representative FACS plots of three independent experiments are shown. (D) Numbers of CD138⁺CD38^hi plasmablasts in GFP (control) and SOX5-GFP-transduced B cells at days 3, 6 and 9 referring to CD38^hi CD138⁺ cells per 1000 GFP⁺ cells at day 0. Cell numbers are depicted as mean ± SD and t-test p-values indicate the significant differences. Summary of three independent experiments are shown.</p

Expression of <i>SOX5</i> transcript variants in human B cells.

<p>(A) Schematic representation of human <i>SOX5</i> transcript variants. Non-coding exons are depicted as open rectangles, partial coding exons - as half open rectangles and coding exons - as filled rectangles. Primer regions are indicated with appropriate arrows. Exons and coding exons are numbered according to their location along the genomic sequence, which are drawn as black lines. (B) RT-PCR analysis for the expression of <i>β-actin</i>, <i>CD19</i> genes and <i>SOX5</i> transcript variants. HD PBMCs were separated into: A – PBMCs; B – B cells and C – non-B lymphocytes. Except for <i>SOX5</i> transcript variant 3 (<i>SOX5</i>-var 3) in which human testis RNA sample served as a control, human costal cartilage cells used as a positive control in all RT-PCR reactions. In agarose gel pictures DNA markers were cut out, since they were loaded between the tested samples and the control sample. (C) RT-PCR assay performed to discriminate between <i>SOX5</i> transcript variant 2 and variant 4 in samples of peripheral blood lymphocytes: A – PBMCs; B – B cells and C – non-B lymphocytes.</p

Expression of <i>SOX5</i> in human B cell subpopulations.

<p>(A) Relative quantification of <i>SOX5</i> by RT-qPCR in peripheral blood naive, MZ-like, switched memory (sw mem), non-classical memory (nc mem) and CD21^low B cells. (B) Relative quantification RT-qPCR assay for <i>SOX5</i> expression in follicular naive, germinal center B cells (GC), memory B cells and plasma cells (PC) from tonsils. T-test p-values indicate the significance of differences between the samples. Relative expression levels of <i>SOX5</i> are shown as mean ± SD. <i>RPLP0</i> gene was used as an internal control in the samples. (C) Immunofluorescence staining for the expression of SOX5 protein in tonsillar tissues. IgD staining was used to stain mantle zones, Ki67 staining for proliferating centroblasts within germinal centers and CD138 as a marker for extrafollicular plasma cells.</p