European Journal of Immunology最新文献

Contrary to short-lived plasma cells, which survive only 3-5 days, long-lived plasma cells (LLPCs) contribute to the humoral memory of the body and thus also to many antibody-related diseases. The ability of plasma cells to persist over months, years, and even a lifetime has been demonstrated in vivo. Yet, the in vitro culture of human primary bone marrow-derived plasma cells has been limited to a few days. Here, we establish culture conditions for human primary bone marrow-derived plasma cells for 21 days. Plasma cells and stromal cells are isolated from human bone marrow and cultured in 2D or a 3D ceramic scaffold. The plasma cells' survival and antibody secretion depend on direct contact with stromal cells. The culture promotes CD19-negative PCs. Inhibition of the PI3K or NF-kappaB pathways using chemical inhibitors reduced the survival of the plasma cells. These results underline the supportive role of the stromal cells for the survival of the LLPC and confirm mechanisms that were identified in mouse LLPCs also for human LLPCs. The culture described here will promote further studies to deepen our understanding of the human LLPC.

Fibroblastic reticular cells (FRCs) are pivotal stromal components that maintain the structure of secondary lymphoid tissues and modulate the immune responses within the lymphoid microenvironment. In response to specific immune or inflammatory stimuli, such as infection or autoimmune triggers, FRCs undergo significant metabolic reprogramming. This process, originally characterized in cancer research, involves the regulation of key metabolic enzymes, pathways, and metabolites, resulting in functional transformations of these cells. Specifically, viruses stimulate FRCs to enhance the tricarboxylic acid cycle, while rheumatoid arthritis and sepsis prompt FRCs to increase oxidative phosphorylation. These changes enable FRCs to adapt their functions, such as proliferation or cytokine secretion, thereby effectively regulating the immune microenvironment to meet the dynamic needs of the immune system. This review provides a comprehensive update on the metabolic reprogramming of FRCs, highlighting how these changes support immune tolerance and response under varied physiological conditions.

The reasons for the low frequency of anti-Ro/SS-A antibody in patients with HTLV-1-associated myelopathy complicated with Sjögren's syndrome (SS) are unclear. In this study, we investigated whether HTLV-1-infected T cells can act directly on B cells and suppress B cells' production of antibodies, including anti-Ro/SS-A antibody. For this purpose, we established an in vitro T-cell-free B-cell antibody production system. The productions of total IgG and anti-cytomegalovirus IgG in B cells from healthy subjects and those of total IgG and anti-Ro/SS-A IgG in B cells from SS patients were significantly suppressed by the addition of HTLV-1-positive T-cell lines (MT-2 and HCT-5). Our analysis of co-cultured B cells identified no sign of HTLV-1 infection and revealed that MT-2 and HCT-5 cells act on the early stages of B-cell differentiation, not the activation stage. MT-2 and HCT-5 cells constitutively expressed CD70, ICAM-1, LAP (TGF-β), and PD-L1/2, but blocking monoclonal antibodies to these molecules or PD-L1/2 receptor PD-1 had no significant canceling effect on B-cell IgG production regarding their suppressive activity. Importantly, autologous CD4⁺CD25⁺CD127^low Treg cells had no inhibitory effect on B-cell IgG production. These results demonstrate that HTLV-1-positive T cells can directly suppress B-cell antibody production through mechanisms that differ from Treg functions.

Tumor cell-intrinsic ubiquitin-conjugating enzyme Ubc13 promotes tumorigenesis, yet how Ubc13 in immune cell compartments regulates tumor progression remains elusive. Here, we show that myeloid-specific deletion of Ubc13 (Ubc13^fl/flLyz2^Cre) leads to accelerated transplanted lung tumor growth in mice. Compared with their littermate controls, tumor-bearing Ubc13^fl/flLyz2^Cre mice had lower proliferation and effector function of CD8⁺ T lymphocytes, accompanied by increased infiltration of myeloid-derived suppressor cells within the tumor microenvironment. Mechanistically, Ubc13 deficiency leads to upregulation of Arg1 and PD-L1, the latter is modulated by reduced Ubc13-mediated K63-linked polyubiquitination and increasing activation of Akt, thereby inducing skewness to protumoral polarization and immunosuppressive manifestation. Taken together, we reveal that macrophage-intrinsic Ubc13 restrains lung tumor progression, indicating that activating Ubc13 in macrophages could be an effective immunotherapeutic regimen for lung cancer.

B cells with low or absent expression of CD21 (CD21^lo B cells) gained attention due to their expansion in the peripheral blood of patients with immune-mediated, rheumatic diseases. This is not only observed in typical autoimmune diseases like systemic lupus erythematosus and Sjögren's disease (SjD) but also in radiographic axial spondyloarthritis (r-axSpA), which is considered an autoinflammatory disease. To gain more insight into the origins of the heterogeneous CD21^lo B-cell population, and its relation to the plasmablast (PB) compartment, we profiled the B-cell-receptor (BCR) repertoire in CD27^- and CD27⁺ fractions of CD21^lo B cells and early PBs using next-generation sequencing. Populations were sorted from peripheral blood of healthy individuals, SjD patients, and r-axSpA patients (n = 10 for each group). In healthy individuals and both patient groups, our findings indicate that CD27^-CD21^lo B cells, which exhibit few mutations in their BCR, may develop into CD27⁺CD21^lo B cells and PBs, both marked by considerably more mutations. Given the known expansion of circulating CD27^-CD21^lo B cells in SjD and r-axSpA patients and clonal relationships with both CD27⁺CD21^lo B cells and early PBs, these cells might actively contribute to (pathological) immune responses in rheumatic diseases with autoimmune and/or autoinflammatory characteristics.

The CD8 co-receptor exists as both an αα homodimer, expressed on subsets of specialized lymphoid cells, and as an αβ heterodimer, which is the canonical co-receptor on cytotoxic T-cells, tuning TCR thymic selection and antigen-reactivity in the periphery. However, the biophysical parameters governing human CD8αβ interactions with classical MHC class I (MHCI) and unconventional MHC-like molecules have not been determined. Using hetero-dimerized Fc-fusions to generate soluble human CD8αβ, we demonstrate similar weak binding affinity to multiple different MHCI alleles compared with CD8αα. We observed that both forms of CD8 bound to certain alleles with stronger affinity than others and found that the affinity of thymically selected TCRs was inversely associated with the affinity of the CD8 co-receptor for the different alleles. We further demonstrated the binding of CD8αα and CD8αβ to the unconventional MHC-like molecule, MHCI-related protein 1, with a similar affinity as for classical MHCI, but no interaction was observed for the other unconventional MHC-like molecules, CD1a, b, c, or d. In summary, this is the first characterization of human CD8αβ binding to MHCI and MHC-like molecules that revealed an intriguing relationship between CD8 binding affinity for different MHCI alleles and the selection of TCRs in the thymus.

Imlifidase (IdeS) is a bacterial protease that hydrolyzes human IgG in their hinge region, decreasing their half-life and abrogating their Fc-mediated properties. It is now successfully used in therapy to prevent graft rejection during kidney transplants and is being clinically evaluated in several IgG-mediated autoimmune diseases. IdeS short half-life however limits its clinical use, particularly in the case of chronic diseases that would request repeated administrations. Here, we developed IdeS-Fc fusion proteins as a divalent homodimer (IdeS-Fc^div) or a monovalent heterodimer (IdeS-Fc^monov), in order to extend the IgG-depleting action of IdeS over time. Both IdeS-Fc efficiently separated monoclonal and polyclonal human IgG into F(ab')₂ and Fc fragments, although with slower kinetics than their native counterpart. IdeS-Fc^monov exhibited a seven-fold half-life extension in vivo as compared with IdeS, and a significantly better residual cleavage of human IgG at later time points after injection. Our results provide proof of concept for the use of an IdeS with extended IgG-hydrolyzing functions in vivo that could rapidly translate to the clinic.

Genetic engineering of regulatory T cells (Tregs) presents a promising avenue for advancing immunotherapeutic strategies, particularly in autoimmune diseases and transplantation. This study explores the modification of Tregs via mRNA electroporation, investigating the influence of T-cell activation status on transfection efficiency, phenotype, and functionality. For this CD45RA⁺ Tregs were isolated, expanded, and modified to overexpress brain-derived neurotrophic factor (BDNF). Kinetics of BDNF expression and secretion were explored. Treg activation state was assessed by checking the expression of activation markers CD69, CD71, and CD137. Our findings show that only activated Tregs secrete BDNF post-genetic engineering, even though both activated and resting Tregs express BDNF intracellularly. Notably, the mTOR pathway and CD137 are implicated in the regulation of protein secretion in activated Tregs, indicating a complex interplay of signalling pathways. This study contributes to understanding the mechanisms governing protein expression and secretion in engineered Tregs, offering insights for optimizing cell-based therapies and advancing immune regulation strategies.

Helicobacter infection is a key cause of gastric B cell mucosa-associated lymphoid tissue (MALT) lymphoma. This study examined the role of B cell-activating factor (BAFF), a major driver of B cell proliferation and many B cell disorders, in this malignancy using a model in which conditional knockout mice for NOD-like receptor family CARD domain-containing 5 (Nlrc5) are infected with Helicobacter felis. Gastric BAFF production was significantly increased in H. felis-infected Nlrc5^mø-KO mice compared to wild-type. Blocking BAFF signalling, before or after the onset of Helicobacter-induced gastritis, significantly reduced MALT development, with fewer gastric B cell follicles and reduced gland hyperplasia. BAFF blockade also reshaped the immune cell landscape in the stomach, resulting in fewer CD4⁺ T cells, Tregs, macrophages and dendritic cells. Using a cell culture model, we identified the protein-coding BAFF transcripts that are upregulated in NLRC5-deficient macrophages stimulated with either H. felis or the NLRC5 agonist, lipopolysaccharide. Among the upregulated variants, TNFSF13B (BAFF)-206 acts as a transcription factor and is reported to enhance BAFF production in autoimmune diseases and cancer. Altogether, these findings implicate the NLRC5-BAFF signalling axis in Helicobacter-induced B cell MALT lymphoma, highlighting BAFF inhibition as a potential therapeutic approach.

The human fetal immune system starts to develop in the first trimester and likely plays a crucial role in fetal development and maternal-fetal tolerance. Innate lymphoid cells (ILCs) are the earliest lymphoid cells to arise in the human fetus. ILCs consist of natural killer (NK) cells, ILC1s, ILC2s, and ILC3s that all share a common lymphoid origin. Here, we studied fetal ILC subsets, mainly NK cells and ILC3s and their potential progenitors, across human fetal tissues. Our results show that fetal ILC subsets have distinct distribution, developmental kinetics, and gene expression profiles across human fetal tissues. Furthermore, we identify CD34⁺RORγt⁺Eomes^- and CD34⁺RORγt⁺Eomes⁺ cells in the fetal intestine, indicating that tissue-specific ILC progenitors exist already during fetal development.