bioRxiv Science⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/2019.12.13.872820

Intravital quantification of absolute cytoplasmic B cell calcium reveals dynamic signaling across B cell differentiation stages

Ulbricht, C.·Leben, R.·Rakhymzhan, A.·Kirchhoff, F.·Nitschke, L.·Radbruch, H.·Niesner, R. A.·Hauser, A. E.
View original source ↗Export metadata ↓

Abstract

Development, function and maintenance of lymphocytes largely depend upon the cellular mobilization and storage of Ca2+ ions. In B lymphocytes, the absolute amount of calcium mobilized and retained after cell signaling remains unknown, athough it is a crucial part of their selection within germinal centers and differentiation into plasma cells. Here, we introduce the novel reporter mouse strain YellowCaB that expresses the genetically encoded calcium indicator TN-XXL in CD19+ lymphocytes. The construct consists of the electrondonor fluorophore eCFP and the acceptor citrine, linked by a calcium sensitive domain. Its conformation and therefore donor quenching is directly linked to cytosolic calcium concentrations. By combining intravital two-photon fluorescence lifetime microscopy with our numerical approach for phasor-based analysis, we are able to extract absolute cytoplasmic calcium concentrations in activated B cells for the first time in vivo. We show that calcium concentrations in B cells are highly dynamic and fluctuations persist in extrafollicular B cells with functional relevance.

Source connections

Explore related subjects

immunologyPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Ulbricht, C., Leben, R., Rakhymzhan, A., Kirchhoff, F., Nitschke, L., Radbruch, H., Niesner, R. A., Hauser, A. E.. 2019-12-13. Intravital quantification of absolute cytoplasmic B cell calcium reveals dynamic signaling across B cell differentiation stages. https://doi.org/10.1101/2019.12.13.872820

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

De novo design of CR2 binder as vaccine scaffold

Efficient B cell activation during vaccine-induced humoral immunity relies on both B cell receptor (BCR) antigen recognition and synergistic signaling from co-receptors. Complement receptor 2 (CR2), the primary BCR co-receptor on B cells, lowers the activation threshold and amplifies downstream kinase signaling by orders of magnitude when engaged by complement fragment C3d decorated antigens. Targeting CR2 therefore represents a rational vaccine enhancement strategy, yet native C3d suffers from low affinity, poor stability, and manufacturing challenges. Here, we report the de novo design of a highly stable, high-affinity CR2 binder using deep learning driving protein design methods. Biophysical characterization, high-resolution cryoEM structural determination, and functional assays in vitro and in vivo confirm that the designed binder matches computational design models and specifically engages CR2 to boost B cell activation. When fused to antigen as a vaccine scaffold, the trimeric CR2 binder elicits robust humoral immune responses comparable to nanoparticle vaccines, while retaining the simplicity of single-chain protein production. Our work establishes a modular CR2 targeting vaccine scaffold platform with broad translational potential for next-generation protein vaccines.

immunology↗
bioRxiv2026

Chronic opioid-associated immune dysregulation among people living with HIV

Objectives: Persistent immune dysregulation contributes to chronic disease among people living with HIV (PWH), even after viral suppression with antiretroviral therapy (ART). Although chronic opioid exposure is associated with adverse clinical outcomes, its impact on immune homeostasis during ART remains incompletely understood. We investigated whether opioid use disorder (OUD) is associated with persistent systemic and cellular immune dysregulation despite ART-mediated reductions in HIV viral load (VL). Methods: Peripheral blood was collected longitudinally from PWH with OUD (PWH/OUD+) and detectable HIV VL during 6 months of optimized ART (months 0, 3, and 6). A reference cohort of PWH without OUD (PWH/OUD-) and suppressed HIV VL provided a single blood sample. Immune profiling included plasma inflammatory biomarkers, multiplex cytokine analyses, spectral flow cytometry, and assessment of monocyte cytokine responses following lipopolysaccharide (LPS) stimulation. Mixed-effects models adjusted for HIV VL and VL-stratified analyses were performed. Results: PWH/OUD+ exhibited persistent immune dysregulation despite reductions in HIV VL. Plasma sCD163, sCD14, fractalkine, and I-TAC remained elevated, whereas TGF-{beta}1 was reduced. OUD was associated with expansion of CD16 monocytes and altered expression of CCR2, CD38, and CD11b. CD4 and CD8 T cells, NK cells, and B cells also exhibited persistent alterations in markers of activation, metabolism, and trafficking. Monocytes from PWH/OUD+ displayed attenuated cytokine responses following LPS stimulation. Conclusions: OUD is associated with persistent systemic and cellular immune dysfunction in PWH despite ART-mediated viral suppression, supporting opioid exposure as an independent contributor to chronic immune dysregulation that may promote inflammation, immune dysfunction, and long-term HIV-associated comorbidities. Keywords: HIV, Opioid-use disorder, innate immunity, cytokine

immunology↗
bioRxiv2026

The mitochondrial RNA extrusion-induced innate immunity is regulated by N6-methyladenosine machinery

Mitochondrial RNA (mtRNA) released into the cytosol functions as a damage associated molecular pattern that activates pattern-recognition receptor (PRR)-mediated inflammation, yet its release mechanisms and cytoplasmic fate remain poorly understood. Here we report that chemical Abt-373-treatment and Vesicular stomatitis virus (VSV) infection induce mtRNA extrusion through Bax/Bak and VDAC1 channels, accompanied by mtDNA release. Extruded mtRNA in A549 cells activates multiple cytosolic PRRs, including RIG-I, MDA5, TLR3/7/8, and PKR, each contributing differentially to the innate immune signaling. Analysis of GEO datasets and methylated RNA immunoprecipitation (MeRIP) assays further reveals that mtRNA carries methyladenosine (m6A) modification. m6A machinery proteins are involved in the cytoplasmic retention time of mtRNA and its interaction with RIG-I, thereby modulating mtRNA-induced innate immunity. Thus, our work establishes in vitro models of mtRNA extrusion, and highlights m6A-dependent modulation as a potential therapeutic target for mtRNA-driven inflammation.

immunology↗