Two recent studies reveal that the extent of fitness or anergy in tumor-associated memory B cells is vital to anti-tumor immune response, cancer patient survival, and response to immune therapy. The impact of these seminal findings demonstrates the untapped potential for using B cells to combat the lethality of cancer.

Natural killer (NK) cells are critical to the innate immune system, as they recognize antigens without prior sensitization, and contribute to the control and clearance of viral infections and cancer. However, a significant proportion of NK cells in mice and humans do not express classical inhibitory receptors during their education process and are rendered naturally \"anergic\", i.e., exhibiting reduced effector functions. The molecular events leading to NK cell anergy as well as their relation to those underlying NK cell exhaustion that arises from overstimulation in chronic conditions, remain unknown. Here, we characterize the \"anergic\" phenotype and demonstrate functional, transcriptional, and phenotypic similarities to the \"exhausted\" state in tumor-infiltrating NK cells. Furthermore, we identify zinc finger transcription factor Egr2 and diacylglycerol kinase DGKα as common negative regulators controlling NK cell dysfunction. Finally, experiments in a 3D organotypic spheroid culture model and an in vivo tumor model suggest that a nanoparticle-based delivery platform can reprogram these dysfunctional natural killer cell populations in their native microenvironment. This approach may become clinically relevant for the development of novel anti-tumor immunotherapeutic strategies.

T cells that encounter self-antigens after exiting the thymus avert autoimmunity through peripheral tolerance. Pathways for this include an unresponsive state known as anergy, clonal deletion, and T regulatory (Treg) cell induction. The transcription factor cues and kinetics that guide distinct peripheral tolerance outcomes remain unclear. Here, we found that anergic T cells are epigenetically primed for regulation by the non-classical AP-1 family member BATF. Tolerized BATF-deficient CD4+ T cells were resistant to anergy induction and instead underwent clonal deletion due to proapoptotic BIM (Bcl2l11) upregulation. During prolonged antigen exposure, BIM derepression resulted in fewer PD-1+ conventional T cells as well as loss of peripherally induced FOXP3+ Treg cells. Simultaneous Batf and Bcl2l11 knockdown meanwhile restored anergic T cell survival and Treg cell maintenance. The data identify the AP-1 nuclear factor BATF as a dominant driver of sustained T cell anergy and illustrate a mechanism for divergent peripheral tolerance fates.

Insulin-specific B cells called BND2 B cells accumulate in the peripheral blood of patients with very early onset type 1 diabetes.

Sepsis is a life-threatening condition with high mortality. A few studies have emerged utilizing single-cell RNA sequencing (scRNA-seq) to analyze gene expression at the single-cell resolution in sepsis, but a comprehensive high-resolution analysis of blood antigen-presenting cells has not been conducted.
All published human scRNA-seq data were downloaded from the single cell portal database. After manually curating the dataset, we extracted all antigen-presenting cells, including dendritic cells (DCs) and monocytes, for identification of cell subpopulations and their gene profiling and intercellular interactions between septic patients and healthy controls. Finally, we further validated the findings by performing deconvolution analysis on bulk RNA sequencing (RNA-seq) data and flow cytometry.
Within the traditional DC populations, we discovered novel anergic DC subtypes characterized by low major histocompatibility complex class II expression. Notably, these anergic DC subtypes showed a significant increase in septic patients. Additionally, we found that a previously reported immunosuppressive monocyte subtype, Mono1, exhibited a similar gene expression profile to these anergic DCs. The consistency of our findings was confirmed through validation using bulk RNA-seq and flow cytometry, ensuring accurate identification of cell subtypes and gene expression patterns.
This study represents the first comprehensive single-cell analysis of antigen-presenting cells in human sepsis, revealing novel disease-associated anergic DC subtypes. These findings provide new insights into the cellular mechanisms of immune dysregulation in bacterial sepsis.

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Autoreactive B cells are not entirely deleted, but some remain as immunocompetent or anergic B cells. Although the persistence of autoreactive B cells as anergic cells has been shown in transgenic mouse models with the expression of B cell receptor (BCR) reactive to engineered self-antigen, the characterization of naturally occurring anergic B cells is important to identify them and understand their contribution to immune regulation or autoimmune diseases. We report here that a low-level expression of CD138 in the splenic B cells marks naturally arising anergic B cells, not plasma cells. The CD138int B cells consisted of IgMlowIgDhigh follicular (FO) B cells and transitional 3 B cells in homeostatic conditions. The CD138int FO B cells showed an anergic gene expression profile shared with that of monoclonal anergic B cells expressing engineered BCRs and the gene expression profile was different from those of plasma cells, age-associated B cells, or germinal center B cells. The anergic state of the CD138int FO B cells was confirmed by attenuated Ca2+ response and failure to upregulate CD69 upon BCR engagement with anti-IgM, anti-IgD, anti-Igκ, or anti-IgG. The BCR repertoire of the CD138int FO B cells was distinct from that of the CD138- FO B cells and included some class-switched B cells with low-level somatic mutations. These findings demonstrate the presence of polyclonal anergic B cells in the normal mice that are characterized by low-level expression of CD138, IgM downregulation, reduced Ca2+ and CD69 responses upon BCR engagement, and distinct BCR repertoire.

The origin of the impaired CD4 T-cell response and immunodeficiency of HIV-infected patients is still only partially understood. We recently demonstrated that PLA2G1B phospholipase synergizes with the HIV gp41 envelope protein in HIV viremic plasma to induce large abnormal membrane microdomains (aMMDs) that trap and inactivate physiological receptors, such as those for IL-7. However, the mechanism of regulation of PLA2G1B activity by the cofactor gp41 is not known. Here, we developed an assay to directly follow PLA2G1B enzymatic activity on CD4 T-cell membranes. We demonstrated that gp41 directly binds to PLA2G1B and increases PLA2G1B enzymatic activity on CD4 membrane. Furthermore, we show that the conserved 3S sequence of gp41, known to bind to the innate sensor gC1qR, increases PLA2G1B activity in a gC1qR-dependent manner using gC1qR KO cells. The critical role of the 3S motif and gC1qR in the inhibition of CD4 T-cell function by the PLA2G1B/cofactor system in HIV-infected patients led us to screen additional microbial proteins for 3S-like motifs and to study other proteins known to bind to the gC1qR to further investigate the role of the PLA2G1B/cofactor system in other infectious diseases and carcinogenesis. We have thus extended the PLA2G1B/cofactor system to HCV and Staphylococcus aureus infections and additional pathologies where microbial proteins with 3S-like motifs also increase PLA2G1B enzymatic activity. Notably, the bacteria Porphyromonas gingivalis, which is associated with pancreatic ductal adenocarcinoma (PDAC), encodes such a cofactor protein and increased PLA2G1B activity in PDAC patient plasma inhibits the CD4 response to IL-7. Our findings identify PLA2G1B/cofactor system as a CD4 T-cell inhibitor. It involves the gC1qR and disease-specific cofactors which are gC1qR-binding proteins that can contain 3S-like motifs. This mechanism involved in HIV-1 immunodeficiency could play a role in pancreatic cancer and several other diseases. These observations suggest that the PLA2G1B/cofactor system is a general CD4 T-cell inhibitor and pave the way for further studies to better understand the role of CD4 T-cell anergy in infectious diseases and tumor escape.

The BCR comprises a membrane-bound Ig that is noncovalently associated with a heterodimer of CD79A and CD79B. While the BCR Ig component functions to sense extracellular Ag, CD79 subunits contain cytoplasmic ITAMs that mediate intracellular propagation of BCR signals critical for B cell development, survival, and Ag-induced activation. CD79 is therefore an attractive target for Ab and chimeric Ag receptor T cell therapies for autoimmunity and B cell neoplasia. Although the mouse is an attractive model for preclinical testing, due to its well-defined immune system, an obstacle is the lack of cross-reactivity of candidate therapeutic anti-human mAbs with mouse CD79. To overcome this problem, we generated knockin mice in which the extracellular Ig-like domains of CD79A and CD79B were replaced with human equivalents. In this study, we describe the generation and characterization of mice expressing chimeric CD79 and report studies that demonstrate their utility in preclinical analysis of anti-human CD79 therapy. We demonstrate that human and mouse CD79 extracellular domains are functionally interchangeable, and that anti-human CD79 lacking Fc region effector function does not cause significant B cell depletion, but induces 1) decreased expression of plasma membrane-associated IgM and IgD, 2) uncoupling of BCR-induced tyrosine phosphorylation and calcium mobilization, and 3) increased expression of PTEN, consistent with the levels observed in anergic B cells. Finally, anti-human CD79 treatment prevents disease development in two mouse models of autoimmunity. We also present evidence that anti-human CD79 treatment may inhibit Ab secretion by terminally differentiated plasmablasts and plasma cells in vitro.

CD21low age-associated or atypical memory B cells are autoantibody enriched and poised for plasma cell differentiation. These cells overaccumulate in chronic infections, autoimmune disease, and immunodeficiency, posing the question of what checkpoints normally oppose their accumulation. Here, we reveal a critical role for paralogous calcium-NFAT-regulated transcription factors EGR2 and EGR3 that are induced in self-reactive B cells. CD21low and B1 B cells lacking EGR2 and EGR3 accumulate and circulate in young mice in numbers 10- to 20-fold greater than normal and overexpress a large set of EGR2 ChIP-seq target genes, including known drivers of plasma cell differentiation. Most follicular B cells constitutively express Egr2 proportionally to surface IgM downregulation by self-antigens, and EGR2/3 deficiency abolishes this cardinal feature of B cell anergy. These results explain the cardinal features of B cell anergy, define a key transcriptional checkpoint repressing CD21low B cell formation, and inform how NFATC1 or EGR2 mutations promote B1 cell-derived chronic lymphocytic leukemias.