Biology subjects

Schuh, W.

Publications and source records attributed to Schuh, W..

4 recordsLinked to original sources

bioRxiv2026

IgA plasma cells co-secrete monomeric and dimeric IgA

Dimeric immunoglobulin A (dIgA) is generated from IgA monomers (mIgA) via JCHAIN-dependent polymerization. DIgA is transported across epithelial barriers by the poly Ig receptor (PIGR) and confers mucosal protection, while serum contains substantial amounts of IgA monomers. Distinct plasma cell subsets have been proposed to produce either monomeric or dimeric IgA, with bone marrow plasma cells as a primary source of mIgA. Here, we addressed whether IgA plasma cell populations segregate based on mIgA or dIgA production. Flow cytometric analysis of antibody-secreting cells from bone marrow, lymphoid and mucosal tissues revealed universal intracellular JCHAIN expression across isotypes and failed to identify a discrete JCHAIN-negative IgA plasma cell population. To detect polymeric IgA, we generated a recombinant soluble PIGR that selectively bound JCHAIN-containing dIgA in Western blot, ELISA, and flow cytometry. Soluble PIGR binding was detected in all IgA plasma cells irrespective of tissue origin, arguing against a dedicated mIgA-producing plasma cell subset incapable of dIgA formation. Ex vivo cultures and single-cell DropMap secretion assays demonstrated that bone marrow and lamina propria IgA antibody-secreting cells co-secrete mIgA and dIgA. These findings suggest that dIgA assembly and secretion are general properties of IgA plasma cells and disfavor a dedicated mIgA-producing population. HighlightsO_LIAll plasma cells express JCHAIN protein C_LIO_LIRecombinant poly Ig receptor detects dimeric IgA in all IgA plasma cells C_LIO_LIBone marrow plasma cells secrete dimeric IgA C_LIO_LIIgA plasma cells co-secrete mono- and dimeric IgA C_LI

immunology↗

bioRxiv2022

The microRNA processing subunit DGCR8 is required for a T cell-dependent germinal center response

We have previously shown that the microRNA (miRNA) processor complex consisting of the RNAse Drosha and the DiGeorge Critical Region (DGCR) 8 protein is essential for central B cell maturation. To determine whether miRNA processing is required to initiate T cell-mediated antibody responses, we deleted DGCR8 in maturing B-2 cells by crossing a mouse with loxP-flanked DGCR8 alleles with a CD23-Cre mouse. As expected, non-immunized mice showed reduced numbers of mature B-2 cells and IgG-secreting cells and diminished serum IgG titers. In accordance, germinal centers and antigen-specific IgG-secreting cells were absent in mice immunized with T cell-dependent antigens. Therefore, DGCR8 is required to mount an efficient T cell-dependent antibody response. However, DGCR8 deletion in B-1 cells was incomplete, which explains relatively unaffected B-1 cell numbers and adequate IgM and IgA titers in DGCR8-knock out mice and suggests that this mouse model could be used to analyze B-1 responses in the absence of functional B-2 cells.

immunology↗

bioRxiv2021

A pair of non-competing neutralizing human monoclonal antibodies protecting from disease in a SARS-CoV-2 infection model

TRIANNI mice carry an entire set of human immunoglobulin V region gene segments and are a powerful tool to rapidly generate human monoclonal antibodies. After immunizing these mice against the spike protein of SARS-CoV-2, we identified 29 hybridoma antibodies that reacted with the SARS-CoV-2 spike protein. Nine antibodies neutralized SARS-CoV-2 infection at IC50 values in the subnanomolar range. ELISA-binding studies and DNA sequence analyses revealed one cluster of clonally related neutralizing antibodies that target the receptor-binding domain and compete with the cellular receptor hACE2. A second cluster of neutralizing antibodies binds to the N-terminal domain of the spike protein without competing with the binding of hACE2 or cluster 1 antibodies. SARS-CoV-2 mutants selected for resistance to an antibody from one cluster are still neutralized by an antibody from the other cluster. Antibodies from both clusters markedly reduced viral spread in mice transgenic for human ACE2 and protected the animals from SARS-CoV-2 induced weight loss. Thus, we report two clusters of potent non-competing SARS-CoV-2 neutralizing antibodies providing potential candidates for therapy and prophylaxis of COVID-19. The study further supports the use of transgenic animals with human immunoglobulin gene repertoires in pandemic preparedness initiatives.

immunology↗

bioRxiv2021

Mitochondrial function is essential for humoral immunity by controlling flux of the TCA cycle, phosphatidic acid and mTOR activity in B cells

The function of mitochondrial respiration during B cell fate decisions and differentiation remains equivocal. This study reveals that selection for mitochondrial fitness occurs during B cell activation and is essential for subsequent plasma cell differentiation. By expressing a mutated mitochondrial helicase in transitional B cells, we depleted mitochondrial DNA during B cell maturation, resulting in reduced oxidative phosphorylation. Although no changes in follicular B cell development were evident, germinal centers, class switch recombination to IgG, plasma cell generation and humoral immunity were diminished. Defective oxidative phosphorylation led to aberrant flux of the tricarboxylic acid cycle and lowered the amount of saturated phosphatidic acid. Consequently, MTOR activity and BLIMP-1 induction were curtailed whereas HIF1, glycolysis and AMPK activity were amplified. Exogenous phosphatidic acid increased mTOR activity in activated B cells. Hence, mitochondrial function is required and selected for in activated B cells for the successful generation of functional plasma cells.

immunology↗