In an era of predicted emerging pandemics, the production of effective vaccines may require an in-depth understanding of the biology of human naive B (BN) cells. Here we provide evidence that the majority of BN cells expressed CD73, an ecto-5'-nucleotidase often associated with immune cell suppression, and demonstrated features of anergy, including an IgMlowIgD+ surface phenotype, reduced calcium flux in response to IgM crosslinking, and increased PTEN expression. Analysis of antibody sequences encoded by the inherently autoreactive VH4-34 heavy chain produced by plasmablasts seven days following influenza vaccination showed that in younger but not in older individuals, anergic BN cells provided a reservoir of B cells capable of responding to vaccination by somatic mutation, resulting in diversification and loss of autoreactivity. These results suggest that effective human vaccines may require the ability to awaken or 'redeem' anergic BN cells that can be repurposed to participate in pathogen-specific responses.
© 2025. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.

Cells of the myeloid lineage, particularly monocytes and macrophages, play a key role in HIV infection by contributing to viral replication, immune response, and maintaining immune balance during suppressive therapy. We hypothesized that metabolic reprogramming and altered chemokine signaling in people living with HIV (PWH) on long-term antiretroviral therapy (ART) affect monocyte transport and polarization due to ongoing inflammation. Therefore, the present study aimed to identify the mechanism of impaired monocyte/macrophage function in PWH on well-treated ART that can lead to clinical intervention strategies to improve health. Single-cell RNA sequencing, immune-phenotyping, and metabolic modeling identified altered expression of chemokine and metabolite receptors and altered metabolic flux in PWH monocytes that decreased monocyte migration. The plasma secretome revealed a nonclassical inflammatory microenvironment in PWH. Integrative multi-omics and single-cell proteomics of differentiated monocyte-derived macrophages (MDMs) detected metabolic reprogramming orchestrated by α-ketoglutarate (AKG) that affected macrophage function and HIV infection. Increased levels of AKG in plasma were shown to occur in PWH under ART. Therefore, when differentiating MDM with serum from PWH or AKG, macrophage function was found polarized towards an M2-like state. AKG alone was shown to increase CCR5 levels and increase HIV-1 infection in MDM. Here, we utilize systems biology-driven identification and ex vivo assays to show impaired macrophage polarization, due to metabolic training, can leads to a low-grade nonclassical inflammatory environment in well-treated PWH.

Plasmacytoid dendritic cells (pDCs) are capable of triggering broad immune responses, yet, their scarcity in blood coupled to their reduced functionality in cancer, makes their therapeutic use for in situ activation or vaccination challenging.
We designed an in vitro differentiation protocol tailored for human pDCs from cord blood (CB) hematopoietic stem cells (HSCs) with StemRegenin 1 (SR-1) and GM-CSF supplementation. Next, we evaluated the identity and function of CB-pDCs compared to human primary pDCs. Furthermore, we tested the potential of CB-pDCs to support anti-tumor immune responses in co-culture with tumor explants from CRC patients.
Here, we report an in vitro differentiation protocol enabling the generation of 200 pDCs per HSC and highlight the role of GM-CSF and SR-1 in CB-pDC differentiation and function. CB-pDCs exhibited a robust resemblance to primary pDCs phenotypically and functionally. Transcriptomic analysis confirmed strong homology at both, baseline and upon TLR9 or TLR7 stimulation. Further, we could confirm the potential of CB-pDCs to promote inflammation in the tumor microenvironment by eliciting cytokines associated with NK and T cell recruitment and function upon TLR7 stimulation ex vivo in patient tumor explants.
This study highlights CB-pDCs as surrogates for primary pDCs to investigate their biology and for their potential use as cell therapy in cancer.
Copyright © 2024 Fiore, Weckwarth, Paetzold, Albertí Servera, Gies, Rosenhauer, Antoniolli, Nassiri, Schmeing, Dettling, Soni, Majety, Krug, Hoves and Wolf.

AXL+ Siglec-6+ dendritic cells (ASDC) are novel myeloid DCs which can be subdivided into CD11c+ and CD123+ expressing subsets. We showed for the first time that these two ASDC subsets are present in inflamed human anogenital tissues where HIV transmission occurs. Their presence in inflamed tissues was supported by single cell RNA analysis of public databases of such tissues including psoriasis diseased skin and colorectal cancer. Almost all previous studies have examined ASDCs as a combined population. Our data revealed that the two ASDC subsets differ markedly in their functions when compared with each other and to pDCs. Relative to their cell functions, both subsets of blood ASDCs but not pDCs expressed co-stimulatory and maturation markers which were more prevalent on CD11c+ ASDCs, thus inducing more T cell proliferation and activation than their CD123+ counterparts. There was also a significant polarisation of naïve T cells by both ASDC subsets toward Th2, Th9, Th22, Th17 and Treg but less toward a Th1 phenotype. Furthermore, we investigated the expression of chemokine receptors that facilitate ASDCs and pDCs migration from blood to inflamed tissues, their HIV binding receptors, and their interactions with HIV and CD4 T cells. For HIV infection, within 2 hours of HIV exposure, CD11c+ ASDCs showed a trend in more viral transfer to T cells than CD123+ ASDCs and pDCs for first phase transfer. However, for second phase transfer, CD123+ ASDCs showed a trend in transferring more HIV than CD11c+ ASDCs and there was no viral transfer from pDCs. As anogenital inflammation is a prerequisite for HIV transmission, strategies to inhibit ASDC recruitment into inflamed tissues and their ability to transmit HIV to CD4 T cells should be considered.
Copyright: © 2024 Warner van Dijk 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.

Type I interferons (IFN-I) are important mediators of antiviral immunity and autoimmune diseases. Female plasmacytoid dendritic cells (pDCs) exert an elevated capacity to produce IFN-I upon toll-like receptor 7 (TLR7) activation compared to male pDCs, and both sex hormones and X-encoded genes have been implicated in these sex-specific differences. Using longitudinal samples from a trans men cohort receiving gender-affirming hormone therapy (GAHT), the impact of testosterone injections on TLR7-mediated IFN-I production by pDCs was assessed. Single-cell RNA analyses of pDCs showed downregulation of IFN-I-related gene expression signatures but also revealed transcriptional inter-donor heterogeneity. Longitudinal quantification showed continuous reduction of IFN-I protein production by pDCs and reduced expression of IFN-I-stimulated genes in peripheral blood mononuclear cells (PBMCs). These studies in trans men demonstrate that testosterone administration reduces IFN-I production by pDCs over time and provide insights into the immune-modulatory role of testosterone in sex-specific IFN-I-mediated immune responses.
© 2023 The Author(s).