The gut microbiome contributes to chronic inflammatory responses in ulcerative colitis (UC), but molecular mechanisms and disease-relevant effectors remain unclear. Here we analyze the pro-inflammatory properties of colonic fluid obtained during colonoscopy from UC and control patients. In patients with UC, we find that the pelletable effector fraction is composed mostly of bacterial extracellular vesicles (BEVs) that exhibit high IgA-levels and incite strong pro-inflammatory responses in IgA receptor-positive (CD89+) immune cells. Biopsy analyses reveal higher infiltration of CD89+ immune cells in the colonic mucosa from patients with UC than control individuals. Further studies show that IgA-coated BEVs, but not host-derived vesicles nor soluble IgA, are potent activators of pro-inflammatory responses in CD89+ cells. IgA-coated BEVs also exacerbate intestinal inflammation in a dextran sodium sulfate colitis model using transgenic mice expressing human CD89. Our data thus implicate a link between IgA-coated BEVs and intestinal inflammation via CD89+ immune cells, and also hint a potential new therapeutic target for UC.
© 2025. The Author(s).

The efficacy of immunotherapy in pancreatic ductal adenocarcinoma (PDAC) remains limited. The tumor microenvironment (TME), characterized by the accumulation of suppressive myeloid cells including neutrophils, attributes to immunotherapy resistance in PDAC. IgA monoclonal antibodies (mAbs) can activate neutrophils to kill tumor cells; this can be further enhanced by blocking the myeloid immune checkpoint CD47. In this study, we investigated the potential of this therapeutic strategy for PDAC. We determined the expression of tumor-associated antigens (TAAs) on PDAC cell lines and fresh patient samples, and the results showed that the TAAs epithelial cell adhesion molecule (EpCAM), trophoblast cell surface antigen 2 (TROP2) and mucin-1 (MUC1), as well as CD47 were consistently expressed on PDAC. In line with this, we showed that IgA mAbs against EpCAM can activate neutrophils to lyse various PDAC cell lines and tumor cells, which can be augmented by addition of CD47 blockade. In addition, we observed that neutrophils were present in patient tumors and expressed the receptor for IgA. In conclusion, our results indicate that a combination of IgA mAb with CD47 blockade is a promising preclinical treatment strategy for PDAC, which merits further investigation.

Sequential dengue virus (DENV) infections often generate neutralizing antibodies against all four DENV serotypes and sometimes, Zika virus. Characterizing cross-flavivirus broadly neutralizing antibody (bnAb) responses can inform countermeasures that avoid enhancement of infection associated with non-neutralizing antibodies. Here, we used single cell transcriptomics to mine the bnAb repertoire following repeated DENV infections. We identified several new bnAbs with comparable or superior breadth and potency to known bnAbs, and with distinct recognition determinants. Unlike all known flavivirus bnAbs, which are IgG1, one newly identified cross-flavivirus bnAb (F25.S02) was derived from IgA1. Both IgG1 and IgA1 versions of F25.S02 and known bnAbs displayed neutralizing activity, but only IgG1 enhanced infection in monocytes expressing IgG and IgA Fc receptors. Moreover, IgG-mediated enhancement of infection was inhibited by IgA1 versions of bnAbs. We demonstrate a role for IgA in flavivirus infection and immunity with implications for vaccine and therapeutic strategies.
Copyright: © 2023 Lubow et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Monoclonal antibodies (mAbs) have revolutionized clinical medicine, especially in the field of cancer immunotherapy. The challenge now is to improve the response rates, as immunotherapy still fails for many patients. Strategies to enhance tumor cell death is a fundamental aim, but relevant model systems for human tumor immunology are lacking. Herein, we have developed a preclinical human immune - three-dimensional (3D) tumor model (spheroids) to map the efficiency of tumor-specific isotypes for improved tumor cell killing. Different anti-CD20 Rituximab (RTX) isotypes alone or in combination, were evaluated for mediating complement-dependent cytotoxicity and antibody-dependent phagocytosis by human monocytic cells in 3D spheroids, in parallel with monolayer cultures, of human CD20+ B-cell lymphomas. We demonstrate that the IgG3 variant of RTX has the greatest tumoricidal effect over other isotypes, and when combined with apoptosis-inducing RTX-IgG2 isotype the therapeutic effect can be substantially enhanced. The results show further that the treatment outcome by RTX isotypes is influenced by tumor morphology and expression of the complement inhibitor CD59. Hence, the human immune-3D tumor model is a clinical relevant and attractive ex vivo system to predict mAbs for best efficacy in cancer immunotherapy.
© 2021 The Authors. European Journal of Immunology published by Wiley-VCH GmbH.

Monoclonal antibodies (mAb) have revolutionized clinical medicine, especially in the field of cancer immunotherapy. The challenge now is to improve the response rates in the patients, as immunotherapy still fails for many patients. Strategies to enhance tumor cell death is a fundamental aim, but relevant model systems for human tumor immunology are lacking. Herein, we have developed a novel pre-clinical human immune – three-dimensional (3D) tumor model (spheroids) to map the efficiency of tumor-specific isotypes for improved tumor cell killing. Different anti-CD20 Rituximab (RTX) isotypes alone or in combination, were evaluated for mediating complement-dependent cytotoxicity and antibody-dependent phagocytosis by human monocytic cells in 3D spheroids, in parallel with monolayer culture, of human CD20 + B-cell lymphoma. We show that the IgG3 variant of RTX has the greatest tumoricidal effect over other isotypes, mediating strong infiltration of monocytic effector cells into 3D spheroids. Hence, the human immune-3D tumor model is an attractive ex vivo system to help filter out mAbs for best efficacy in cancer immunotherapy.