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UNLABELLED: Chimeric antigen receptor (CAR) technology has revolutionized B-cell malignancy treatment by enabling T cells to effectively recognize and target lineage-specific surface antigens. However, CAR T cells show limited efficacy against myeloid neoplasms and solid tumors due to challenges in identifying suitable surface targets. In this study, we present a CAR targeting the intracellular WT1 oncoprotein, cross-presented by surface HLA class II (HLA-II) alleles. WT1-CAR T cells, derived from an antibody raised solely against a WT1 peptide, recognized the WT1330-348 peptide promiscuously presented by 18 out of 20 tested HLA-II alleles, overcoming traditional HLA restrictions. WT1-CAR T cells specifically recognized leukemic cells in a WT1- and HLA-II-dependent manner and mediated an antitumor response in vitro and in vivo. This approach broadens CAR-targetable antigens beyond traditional HLA restrictions and offers a promising therapeutic option to a wide and genetically diverse patient population. SIGNIFICANCE: Leveraging the promiscuous binding of HLA-II-peptide complexes, we developed a CAR T-cell approach targeting an intracellular oncoprotein WT1 presented across diverse HLA-II families. Our study establishes a framework for CAR therapies against intracellular antigens, extending potential CAR T-cell applications to new cancer types and patient populations.

DOI： 10.1158/2643-3230.BCD-25-0230

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Adoptive T cell therapies typically rely on ex vivo CD3/CD28 stimulation, which promotes effector differentiation and limits the persistence of transferred cells. Stem cell-like memory T cells (Tscm), with their capacity for self-renewal and multipotency, represent an ideal therapeutic subset but remain difficult to generate at scale. Here, we present a CD3-independent strategy using artificial antigen-presenting cells expressing a membrane-bound CD28 superagonist (αCD28-aAPCs) to expand CD8+ T cells with Tscm-like features. In naïve CD8+ T cells, αCD28-aAPC stimulation initiates a distinct transcriptional and epigenetic program, marked by high TCF1 expression, metabolic fitness, and resistance to exhaustion-key hallmarks of the Tscm phenotype. Mechanistically, this approach circumvents canonical CD3/TCR signaling and notably avoids induction of IRF4, a key transcription factor that drives BLIMP1 upregulation, TCF1 downregulation, and glycolytic commitment during effector differentiation. Instead, sustained CD28 signaling alone reprograms T cells toward a Tscm-like state. Upon subsequent antigen encounter and CD3 engagement, these αCD28-aAPC-expanded T cells mount robust effector responses while retaining superior persistence and antitumor activity in preclinical models. Our findings reveal an underappreciated role of CD28 signaling in guiding Tscm-like fate through IRF4 suppression and establish a platform for generating durable and functionally potent T cell therapies.

DOI： 10.1073/pnas.2524626123

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T cell independent type II (TI-II) antigens, such as capsular polysaccharides, have multivalent epitopes, which induce B cell activation, plasma cell differentiation and antibody production by strongly cross-linking B cell receptors. However, the mechanism of B cell activation by TI-II antigens remains unclear. In this study, we demonstrate that DNA endonuclease DNase1L3 (also termed DNase γ) is required for the TI-II response. The production of antigen-specific antibodies was severely diminished in DNase1L3-deficient mice upon immunization with TI-II antigens, but not with T cell dependent (TD) antigens. Bone marrow chimeric mice and B cell transfer experiments revealed that B cell-intrinsic DNase1L3 was required for the TI-II response. DNase1L3-deficient B cells were defective in cell proliferation and plasma cell differentiation in the TI-II response in vivo as well as in vitro, which was not rescued by co-culture with DNase1L3-sufficient B cells in vitro, disproving an involvement of a secretory DNase1L3. In vitro stimulation with TI-II antigen transiently increased expression of DNase1L3 and its translocation into the nucleus. RNA-seq analysis of ex vivo B cells that had responded to TI-II antigen in vivo revealed a marked reduction of Myc-target gene sets in DNase1L3-deficient B cells. Expression of IRF4, a gene that Myc targets, was diminished in the ex vivo DNase1L3-deficient B cells, in which forced expression of IRF4 restored the TI-II response in vivo. These data revealed an unexpected role of DNase1L3 in a missing link between B cell receptor signaling and B cell activation in the TI-II response, giving a valuable clue to molecularly dissect this response.

DOI： 10.1093/intimm/dxad001

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IgE Abs are a common mediator of allergic responses and are generally produced in type 2 immune responses to allergens. Allergen stimulation of IgE-bound FcεRI on mast cells or basophils induces the production of chemical mediators and cytokines. In addition, IgE binding to FcεRI without allergen promotes the survival or proliferation of these and other cells. Thus, spontaneously produced natural IgE can increase an individual's susceptibility to allergic diseases. Mice deficient in MyD88, a major TLR signaling molecule, have high serum levels of natural IgE, the mechanism for which remains unknown. In this study, we demonstrated that the high serum IgE levels were maintained from weaning by memory B cells (MBCs). IgE from plasma cells and sera from most Myd88-/- mice, but none of the Myd88+/- mice, recognized Streptococcus azizii, a commensal bacterium overrepresented in the lungs of Myd88-/- mice. IgG1+ MBCs from the spleen also recognized S. azizii. The serum IgE levels declined with the administration of antibiotics and were boosted by challenge with S. azizii in Myd88-/- mice, indicating the contribution of S. azizii-specific IgG1+ MBCs to the natural IgE production. Th2 cells were selectively increased in the lungs of Myd88-/- mice and were activated upon addition of S. azizii in the lung cells ex vivo. Finally, lung nonhematopoietic cells, and CSF1 overproduced therefrom, were responsible for natural IgE production in Myd88-/- mice. Thus, some commensal bacteria may prime the Th2 response and natural IgE production in the MyD88-defective lung environment in general.

DOI： 10.4049/jimmunol.2200888

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Antigens (Ags) with multivalent and repetitive structure elicit IgG production in a T-cell-independent manner. However, the mechanisms by which such T-cell-independent type-2 (TI-2) Ags induce IgG responses remain obscure. Here, we report that B-cell receptor (BCR) engagement with a TI-2 Ag but not with a T-cell-dependent (TD) Ag was able to induce the transcription of Aicda encoding activation-induced cytidine deaminase (AID) and efficient class switching to IgG3 upon costimulation with IL-1 or IFN-α in mouse B cells. TI-2 Ags strongly induced the phosphorylation of protein kinase C (PKC)δ and PKCδ mediated the Aicda transcription through the induction of BATF, the key transcriptional regulator of Aicda. In PKCδ-deficient mice, production of IgG was intact against TD Ag but abrogated against typical TI-2 Ags as well as commensal bacteria, and experimental disruption of the gut epithelial barrier resulted in fatal bacteremia. Thus, our results have revealed novel molecular requirements for class switching in the TI-2 response and highlighted its importance in homeostatic commensal-specific IgG production.

DOI： 10.7554/eLife.72116

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