Benner, I. | Search bioRxiv

bioRxiv2026

Distinct transcriptional programs define human IgG4+ memory B cells

Human immunoglobulin G4 (IgG4) shapes both protective and pathogenic immunity, influencing conditions ranging from allergy and autoimmunity to cancer. However, subclass-specific targeting of memory B cells remains challenging due to limited knowledge of their phenotypic and functional heterogeneity. Here, we show that IgG4+ memory B cells are overrepresented in a niche of FCER2+BAFFR+ memory B cells, can be classified in several subtypes, have a distinct transcription factor profile and are the only memory B cell subset to express sterile IGHE transcripts. While IgG4+ B cells display a unique transcriptional profile, only BAFFR, IL5Rb and the B cell receptor were upregulated on protein level on IgG4+ cells. IgG4+ B cells have normal repertoire diversity, but a distinct germline V-gene usage, suggesting IgG4 responses are driven by specific antigens. By labeling autoreactive B cells, we confirmed that MuSK myasthenia gravis (an archetypal IgG4-mediatedautoimmune disease) patients have a normal memory B cell profile and that autoreactive IgG4+ memory B cells are extremely rare. These results highlight the unique features of IgG4+ B cells, provide insight on potential subclass-specific therapeutic targets and point towards an antigen-driven IgG4 response within a largely non-autoreactive memory B cell pool.

immunology↗

bioRxiv2025

Pandemic Legacy: Medical Facemasks as a Potential Source of Marine Microplastic?

Understanding the main sources of microplastic pollution is key towards developing efficient measures to reduce microplastic loadings to marine waters. Yet identifying the main sources of marine microplastic is challenging. Source tracking should be easier in marine bays where inputs are limited. In 2021 we determined the concentrations and characteristics of microplastics > 300 m in surface waters of Placentia Bay, Newfoundland; a bay with negligible river input in an area of low population density, and no plastic processing plants in the vicinity. Microplastics contributed 2-14% to particulate organic carbon (> 300 m), and concentrations ranged from 0.11 to 0.67 particles m-3, a relatively high level given the regions low population density. Microplastic diversity was low; fiber and fragment concentrations dwarfed those of other shapes, and polypropylene (PP) dominated, with transparent PP fibers specifically contributing near 50% to the total microplastic inventory. The overwhelming dominance of transparent PP fibers, as well as the exceptionally high proportion of long fibers, suggest that a distinctive input of large, transparent PP fibers overlaid "background" inputs from other sources. A ballpark estimate indicates that weathering of medical facemasks used during the COVID-19 pandemic are a likely explanation for the dominance of transparent PP fibers in Placentia Bay in 2021. Similar inputs may have affected many other aquatic environments globally, but might not have been observable in systems where other continuous input pathways are high.

biochemistry↗