Fig. 7: IgA-coated BEVs exacerbate DSS-induced colitis in CD89⁺ mice.

a Timeline of the DSS treatment of CD89^wt/wt (littermates, LM) and CD89^tg/wt (CD89-transgenic, CD89) mice followed by oral gavage with uncoated or IgA-coated BEVs from B. fragilis and L. acidophilus (BEVs^B/L and IgA- BEVs^B/L). Oral gavage with saline served as mock-treated control (co). Created in BioRender. Fleischhacker, D. (2025) https://BioRender.com/hbvosjv. b Colon length determined along endpoint harvest (day 9). c Colon histopathology scores assessed double-blinded from colon harvested at the endpoint (day 9). Scores are the sum of the individual criteria assessment including epithelial alteration, neutrophil infiltration and erosion assigned as follows: 0, absent; 1, focal; 2, present; 3, abundant. d Lipocalin-2 levels determined by ELISA from cecal content harvested at the endpoint (day 9). b–d Data is presented as box plot showing minimum and maximum (whiskers), interquartile range (bounds of the box), median (center) (n = 10 mice/group). Statistical difference was evaluated by Kruskal–Wallis (CD89-transgenic mice receiving IgA-coated BEVs^B/L to all other groups) with Dunn’s test. Source data are provided as a Source Data file. e Representative histology pictures from heamotoxylin and eosin stained colons derived from CD89^wt/wt (littermates, LM) and CD89^tg/wt (CD89-transgenic, CD89) mice receiving saline, uncoated or IgA-coated BEVs from B. fragilis and L. acidophilus (BEVs^B/L and IgA- BEVs^B/L) harvested at the endpoint (day 9). Note that CD89-transgenic mice exhibit intensive neutrophil infiltration, epithelial alteration and erosions, whereas littermates showed no or only minimal signs of inflammation. The experiments were repeated at least 10 times with a similar result. Scale bar = 100 µm. f Representative images showing immunofluorescent stainings of colon tissue derived from CD89^wt/wt (littermates, LM) and CD89^tg/wt (CD89-transgenic, CD89) mice receiving IgA-coated BEVs^B/L harvested at the endpoint (day 9). Tissue specimen were stained with anti-human CD89 (red), anti-mouse CD11b (green) and total nuclei stained with DAPI (blue). The experiments were repeated at least 3 times with a similar result. Scale bar = 50 µm.