Identifying clinical response to daratumumab therapy in relapsed/refractory multiple myeloma using a patient-derived in vitro model.

Response to daratumumab in patients with relapsed/refractory multiple myeloma is heterogeneous, and a reliable biomarker of response is lacking. We aimed to develop a method that identifies response to daratumumab therapy. Patient-derived MM cells were collected before start of daratumumab treatment and were cultured in a hydrogel-based culture system. The extent of antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity in vitro was associated with both clinical response and progression-free survival in corresponding patients. Together, our results demonstrate that in vitro sensitivity to daratumumab therapy in a hydrogel culture with primary MM cells might be used to identify patients most likely to benefit from treatment.

Dinaciclib synergizes with BH3 mimetics targeting BCL-2 and BCL-XL in multiple myeloma cell lines partially dependent on MCL-1 and in plasma cells from patients.

A better understanding of multiple myeloma (MM) biology has led to the development of novel therapies. However, MM is still an incurable disease and new pharmacological strategies are needed. Dinaciclib, a multiple cyclin-dependent kinase (CDK) inhibitor, which inhibits CDK1, 2, 5 and 9, displays significant antimyeloma activity as found in phase II clinical trials. In this study, we have explored the mechanism of dinaciclib-induced death and evaluated its enhancement by different BH3 mimetics in MM cell lines as well as in plasma cells from MM patients. Our results indicate a synergistic effect of dinaciclib-based combinations with B-cell lymphoma 2 or B-cell lymphoma extra-large inhibitors, especially in MM cell lines with partial dependence on myeloid cell leukemia sequence 1 (MCL-1). Simultaneous treatment with dinaciclib and BH3 mimetics ABT-199 or A-1155463 additionally showed a synergistic effect in plasma cells from MM patients, ex vivo. Altered MM cytogenetics did not affect dinaciclib response ex vivo, alone or in combined treatment, suggesting that these combinations could be a suitable therapeutic option for patients bearing cytogenetic alterations and poor prognosis. This work also opens the possibility to explore cyclin-dependent kinase 9 inhibition as a targeted therapy in MM patients overexpressing or with high dependence on MCL-1.

Tumor Desmoide de mama en paciente gestante. A propósito de un caso / Desmoid Tumor in a pregnant pacient´s breast. Case report

El Tumor Desmoide, es un tumor raro de origen mesenquimal con una incidencia aproximada de 0.3% (1) que, si bien es considerado un tumor benigno por no presentar metástasis a distancia, se considera un tumor localmente agresivo con altas tasas de recidiva tras la extirpación quirúrgica de entre el 19 a 28% (2). Se presenta el caso clínico de una mujer de 21 años de edad, gestante de 7 semanas, que acudió a consulta a la Unidad de Mastología del Hospital de Clínicas por percatarse de nódulo en cuadrante superoexterno de mama derecha, que aumenta de tamaño. Se realizó exéresis tumoral con márgenes, cuyo diagnóstico fue un Tumor Desmoide y, posterior resección de márgenes para ampliación. El Tumor Desmoide es poco frecuente de localización mamaria, que fue tratada con cirugía con buena evolución en una mujer gestante, por lo que debe considerarse esta patología en pacientes jóvenes gestantes, como diagnóstico diferencial en nódulos mamarios.

Desmoid tumor is a rare tumor of mesenchymal origin with an approximate incidence of 0.3% (1). Although it is considered a benign tumor because it does not present distant metastases, it is considered a locally aggressive tumor with high rates of recurrence after surgical removal of between 19 to 28% (2). We present the clinical case of a 21-year-old woman, 7 weeks pregnant, who attended the Mastology Unit of the Hospital de Clínicas, after noticing a nodule in the upper outer quadrant of the right breast, which was increasing in size. Tumor excision with margins was performed, whose diagnosis was a Desmoid Tumor, and subsequent resection of margins for amplifying The Desmoid Tumor is rare in the breast and was treated with surgery with a good evolution in a pregnant woman, so this pathology should be considered in young pregnant patients, as a differential diagnosis in breast nodules.

Advances and Perspectives in the Treatment of B-Cell Malignancies.

B-cell malignancies arise from different stages of B-cell differentiation and constitute a heterogeneous group of cancers including B-cell lymphomas, B-cell leukemias, and plasma cell dyscrasias [...].

Direct P70S6K1 inhibition to replace dexamethasone in synergistic combination with MCL-1 inhibition in multiple myeloma.

Novel combination therapies have markedly improved the lifespan of patients with multiple myeloma (MM), but drug resistance and disease relapse remain major clinical problems. Dexamethasone and other glucocorticoids are a cornerstone of conventional and new combination therapies for MM, although their use is accompanied by serious side effects. We aimed to uncover drug combinations that act in synergy and, as such, allow reduced dosing while remaining effective. Dexamethasone and the myeloid cell leukemia 1 (MCL-1) inhibitor S63845 (MCL-1i) proved the most potent combination in our lethality screen and induced apoptosis of human myeloma cell lines (HMCLs) that was 50% higher compared with an additive drug effect. Kinome analysis of dexamethasone-treated HMCLs revealed a reduction in serine/threonine peptide phosphorylation, which was predicted to result from reduced Akt activity. Biochemical techniques showed no dexamethasone-induced effects on FOXO protein or GSK3 but did show a 50% reduction in P70S6K phosphorylation, downstream of the Akt-mTORC1 axis. Replacing dexamethasone by the P70S6K1 isoform-specific inhibitor PF-4708671 (S6K1i) revealed similar and statistically significant synergistic apoptosis of HMCLs in combination with MCL-1i. Interestingly, apoptosis induced by the P70S6K1i and MCL-1i combination was more-than-additive in all 9 primary MM samples tested; this effect was observed for 6 of 9 samples with the dexamethasone and MCL-1i combination. Toxicity on stem and progenitor cell subsets remained minimal. Combined, our results show a strong rationale for combination treatments using the P70S6K inhibitor in MM. Direct and specific inhibition of P70S6K may also provide a solution for patients ineligible or insensitive to dexamethasone or other glucocorticoids.

Curar al alumno, no solo su enfermedad. Descripción de un caso / Healing a student, not just his or her disease. A Case description

INTRODUCCIÓN: En los últimos años las aulas hospitalarias se han configurado como un elemento de gran importancia en la vida de los niños y adolescentes que se encuentran en tratamiento de diferentes enfermedades. Los pacientes de enfermedades oncológicas no son una excepción. OBJETIVO: Aunque las aulas hospitalarias en la actualidad son capaces de sincronizar su trabajo con los colegios de referencia de los pacientes, el propósito de este artículo es presentar y describir un estudio de caso que subraya el papel del aula hospitalaria en sí misma, como una herramienta educativa que es útil en la tarea de educar a sus alumnos de una forma global e inclusiva, sin soslayar los niveles de exigencia adecuados. MÉTODO: Presenta el caso de un adolescente de 16 años diagnosticado de un osteosarcoma localizado que requirió quimioterapia preoperatoria y postoperatoria, cirugía de alta complejidad y finalmente un tratamiento inmunomodulador por un tiempo prolongado. No tenía ningún tipo de actividad académica al haber terminado la etapa de aprendizaje obligatorio y no estaba matriculado en ningún colegio, y a través del Aula Hospitalaria de la Unidad de Hematología y Oncología Pediátrica del Hospital HM Montepríncipe llegó a ser un estudiante interesado y motivado. A pesar de que su enfoque es necesariamente multidisciplinar, este estudio presenta una perspectiva educativa y pone de manifiesto la función, posibilidades, ventajas y desventajas de las aulas hospitalarias y su coordinación con el resto del personal. Lo hace poniendo al paciente en medio de su enfoque, a través de una visión humanística que enfatiza el verdadero significado de la educación. CONCLUSIONES: El propósito de un aula hospitalaria no debe ser solo académico, pues tiene un papel fundamental en el objetivo de que el niño y adolescente con cáncer se convierta en un adulto sano física, psíquica, social y espiritualmente

INTRODUCTION: The importance of hospital schools has been rising during the last decades. They have gained a lot of influence in the lives of children and teenagers under treatment for different diseases. Those in pediatric hematology/oncology units are not an exception. OBJECTIVE: Though the hospital schools are nowadays capable of synchronize their work with the patients' regular schools, the purpose of this project is to present and describe a case report which underlines the role of the hospital schools as themselves, as a teaching tool which is useful in the goal of educating its students in a global and comprehensive way, which includes an adequate level of demand. METHOD: It presents the case of a 16 years old boy diagnosed with a localized osteosarcoma that required preoperative and post-operative chemotherapy, high complexity surgery and, finally, immunomodulatory therapy for a long time. He had not any kind of learning activity, as he had finished the obligatory educational stage and was not enrolled in any school, and through the Hospital School in the Pediatric Hematology/Oncology Unit in the HM Montepríncipe Hospital became an interested and motivated student. Though its approach is necessarily cross-disciplinary, the present report has an educational perspective and it stresses the function, possibilities, advantages and disadvantages of hospital schools within pediatric oncology units and their coordination with the rest of the staff. It does it by putting the patient in the middle of its scope, through a humanist vision that emphasizes the real meaning of education. RESULTS: The purpose of hospital schools should not be just academic, since they have a fundamental role in achieving that children and teenagers with cancer become healthy adults in a physic, psychic, social and spiritual way

Multiple myeloma with 1q21 amplification is highly sensitive to MCL-1 targeting.

Prosurvival BCL-2 family proteins are potent inhibitors of apoptosis and often overexpressed in lymphoid malignancies. In multiple myeloma (MM), MCL-1 expression contributes to survival of malignant plasma cells, and overexpression correlates with poor prognosis. In this study, we investigated whether sensitivity to the novel MCL-1 inhibitor S63845 could be predicted using cytogenetics, focusing on amplification of 1q21, the chromosomal region that contains the MCL1 locus. In addition, we studied the relation of MCL-1 inhibitor sensitivity with other diagnostic characteristics and BCL-2 family protein expression. In 31 human myeloma cell lines and in bone marrow aspirates from 47 newly diagnosed MM patients, we measured the effect of S63845 alone, or combined with BCL-2 inhibitor ABT-199 (venetoclax), and BCL-XL inhibitor A-1155463 or A-1331852 on cell viability. We demonstrated for the first time that MM cells from patients with 1q21 amplification are significantly more sensitive to inhibition of MCL-1. We suggest that this increased sensitivity results from high relative MCL1 expression resulting from amplification of 1q21. Additionally, and partially independent from 1q21 status, high serum ß2 microglobulin level and presence of renal insufficiency correlated with increased sensitivity to MCL-1 inhibitor treatment. Combining S63845 with other BH3 mimetics synergistically enhanced apoptosis compared with single inhibitors, and sensitivity to inhibitor combinations was found in a large proportion of MM insensitive to MCL-1 inhibition alone. Collectively, our data indicate that amplification of 1q21 identifies an MM subset highly sensitive to MCL-1 inhibitor treatment and can be used as a predictive marker to guide selection of therapy.

CD Maps-Dynamic Profiling of CD1-CD100 Surface Expression on Human Leukocyte and Lymphocyte Subsets.

CD molecules are surface molecules expressed on cells of the immune system that play key roles in immune cell-cell communication and sensing the microenvironment. These molecules are essential markers for the identification and isolation of leukocytes and lymphocyte subsets. Here, we present the results of the first phase of the CD Maps study, mapping the expression of CD1-CD100 (n = 110) on 47 immune cell subsets from blood, thymus, and tonsil using an eight-color standardized EuroFlow approach and quantification of expression. The resulting dataset included median antibody binding capacities (ABCs) and percentage of positivity for all markers on all subsets and was developed into an interactive CD Maps web resource. Using the resource, we examined differentially expressed proteins between granulocyte, monocyte, and dendritic cell subsets, and profiled dynamic expression of markers during thymocyte differentiation, T-cell maturation, and between functionally distinct B-cell subset clusters. The CD Maps resource will serve as a benchmark of antibody reactivities ensuring improved reproducibility of flow cytometry-based research. Moreover, it will provide a full picture of the surfaceome of human immune cells and serves as a useful platform to increase our understanding of leukocyte biology, as well as to facilitate the identification of new biomarkers and therapeutic targets of immunological and hematological diseases.

Regulatory roles of IL-10-producing human follicular T cells.

Mucosal lymphoid tissues such as human tonsil are colonized by bacteria and exposed to ingested and inhaled antigens, requiring tight regulation of immune responses. Antibody responses are regulated by follicular helper T (TFH) cells and FOXP3+ follicular regulatory T (TFR) cells. Here we describe a subset of human tonsillar follicular T cells identified by expression of TFH markers and CD25 that are the main source of follicular T (TF) cell-derived IL-10. Despite lack of FOXP3 expression, CD25+ TF cells resemble T reg cells in high CTLA4 expression, low IL-2 production, and their ability to repress T cell proliferation. CD25+ TF cell-derived IL-10 dampens induction of B cell class-switching to IgE. In children, circulating total IgE titers were inversely correlated with the frequencies of tonsil CD25+ TF cells and IL-10-producing TF cells but not with total T reg cells, TFR, or IL-10-producing T cells. Thus, CD25+ TF cells emerge as a subset with unique T and B cell regulatory activities that may help prevent atopy.

The Checkpoint Regulator SLAMF3 Preferentially Prevents Expansion of Auto-Reactive B Cells Generated by Graft-vs.-Host Disease.

Absence of the mouse cell surface receptor SLAMF3 in SLAMF3-/- mice suggested that this receptor negatively regulates B cell homeostasis by modulating activation thresholds of B cell subsets. Here, we examine whether anti-SLAMF3 affects both B and T cell subsets during immune responses to haptenated ovalbumin [NP-OVA] and in the setting of chronic graft vs. host disease (cGVHD) induced by transferring B6.C-H2bm12/KhEg (bm12) CD4+ T cells into B6 WT mice. We find that administering αSLAMF3 to NP-OVA immunized B6 mice primarily impairs antibody responses and Germinal center B cell [GC B] numbers, whilst CXCR5+, PD-1+, and ICOS+ T follicular helper (TFH) cells are not significantly affected. By contrast, administering αSLAMF3 markedly enhanced autoantibody production upon induction of cGVHD by the transfer of bm12 CD4+ T cells into B6 recipients. Surprisingly, αSLAMF3 accelerated both the differentiation of GC B and donor-derived TFH cells initiated by cGVHD. The latter appeared to be induced by decreased numbers of donor-derived Treg and T follicular regulatory (TFR) cells. Collectively, these data show that control of anti-SLAMF3-induced signaling is requisite to prevent autoantibody responses during cGVHD, but reduces responses to foreign antigens.

Viral CD229 (Ly9) homologs as new manipulators of host immunity.

The signaling lymphocytic activation molecule family (SLAMF) of receptors plays crucial roles during innate and adaptive immune responses. The SLAMF member CD229 (Ly9, SLAMF3) is a homophilic receptor predominantly expressed on the surface of B and T cells. CD229 acts as a cosignaling molecule, regulating lymphocyte homoeostasis and activation. To promote viral replication and survival in their hosts, viruses have developed sophisticated mechanisms to combat and avoid immune surveillance. Many of these strategies rely on host defense genes captured during the process of virus-host coevolution. In particular, large DNA viruses devote a wide range of proteins to interfere with almost every host immune pathway. Given that CD229 is critically involved in regulating immune responses, it is not surprising that viruses have designed tactics to mimic or interfere with this receptor. The discovery, in recent years, that some viruses have hijacked CD229 genes from their hosts, incorporating them as an integral part of their genomes, or have evolved proteins to directly target CD229, indicates that this is the case. While it is still an emerging area of research, the present review discusses these viral molecules and their potential in immune modulation. A more detailed understanding of the mechanisms of action and the functional implications of these new viral CD229 mimics may not only provide seminal information on viral immune evasion mechanisms but also, unveil unrecognized aspects of CD229 immune functions.

The impact of body mass index on metatarsalgia surgical outcomes.

INTRODUCTION: Several studies have suggested that an increased body mass index (BMI) is a negative factor for forefoot plantar pain but its influence in the surgical correction of metatarsalgia is unknown. The purpose of the present study is to evaluate the influence of the BMI on the surgical outcomes of metatarsalgia. It has been hypothesized that the higher the BMI, the worse the functional outcomes after metatarsalgia surgical treatment at one year follow-up. MATERIAL AND METHODS: A prospective cohort study that included all patients operated on for third rocker metatarsalgia was conducted. Weil's osteotomy was performed on all the patients operated on. The patients' pre-operative height, weight, and BMI were recorded. The patients were subsequently divided into three groups based on their BMI. There was group 1 or the normal group (18.5 > BMI ≤ 25 kg/m2), group 2 or the overweight group (25 > BMI ≤ 30 kg/m2), and group 3 or the obese group (BMI > 30 kg/m2). Pre-operative, post-operative, and differential AOFAS were used to evaluate and compare the groups. The post-operative VAS was also measured to assess pain. The correlation between the BMI and those variables was also analyzed. RESULTS: After the exclusion criteria were applied, 107 patients were finally assessed. There were 22 patients (20.6%) in group 1, 52 patients (48.6%) in group 2, and 33 patients (30.8%) in group 3. No correlation was observed between the BMI and AOFAS (p > 0.05). Neither were any differences found when the three groups were compared (p > 0.05). Moreover, no correlation between the BMI and the VAS score was observed (p = 0.690). CONCLUSION: Obesity does not negatively influence functional outcomes after surgery for metatarsalgia in short to medium term. Regardless of their BMI, patients with propulsive metatarsalgia improve in functionality after surgical treatment.

CD84 cell surface signaling molecule: An emerging biomarker and target for cancer and autoimmune disorders.

CD84 (SLAMF5) is a member of the SLAM family of cell-surface immunoreceptors. Broadly expressed on most immune cell subsets, CD84 functions as a homophilic adhesion molecule, whose signaling can activate or inhibit leukocyte function depending on the cell type and its stage of activation or differentiation. CD84-mediated signaling regulates diverse immunological processes, including T cell cytokine secretion, natural killer cell cytotoxicity, monocyte activation, autophagy, cognate T:B interactions, and B cell tolerance at the germinal center checkpoint. Recently, alterations in CD84 have been related to autoimmune and lymphoproliferative disorders. Specific allelic variations in CD84 are associated with autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis. In chronic lymphocytic leukemia, CD84 mediates intrinsic and stroma-induced survival of malignant cells. In this review, we describe our current understanding of the structure and function of CD84 and its potential role as a therapeutic target and biomarker in inflammatory autoimmune disorders and cancer.

Ly9 (CD229) Antibody Targeting Depletes Marginal Zone and Germinal Center B Cells in Lymphoid Tissues and Reduces Salivary Gland Inflammation in a Mouse Model of Sjögren's Syndrome.

Sjögren's Syndrome (SjS) is a common chronic autoimmune disease characterized by the B cell hyperactivation, lymphocyte infiltration, and tissue damage of exocrine glands. It can also present life-threatening extraglandular manifestations, such as pulmonary and hepatic involvement, renal inflammation and marginal zone (MZ) B cell lymphoma. Several biologic agents have been tested in SjS but none has shown significant efficacy. Here, we report the effects of Ly9 (CD229) antibody targeting, a cell surface molecule that belongs to the SLAM family of immunomodulatory receptors, using NOD.H-2h4 mice as a model of SjS-like disease. Female mice were treated with anti-Ly9 antibody or isotype control at week 24, when all mice present SjS related autoantibodies, salivary gland infiltrates, and marginal zone (MZ) B cell pool enlargement. Antibody injection depleted key lymphocyte subsets involved in SjS pathology such as MZ, B1, and germinal center B cells in spleen and draining lymph nodes without inducing a general immunosuppression. Importantly, mice receiving anti-Ly9 mAb showed a reduced lymphocyte infiltrate within salivary glands. This reduction may be, in part, explained by the down-regulation of L-selectin and alfa4/beta7 integrin induced by the anti-Ly9 antibody. Furthermore, levels of anti-nuclear autoantibodies were reduced after anti-Ly9 treatment. These data indicate that Ly9 is a potential therapeutic target for the treatment of SjS.

3D reconstruction does not improve agreement and results in an increase in surgical indications in proximal humeral fractures.

The objective of this study is to analyze the effect of different imaging modalities in treatment decision making in proximal humeral fractures. After evaluation of 116 consecutive proximal humeral fractures, observers were asked to give treatment recommendation (conservative vs. surgery). If surgery was proposed, they were told to select surgery of choice. When 3D imaging was added, complexity of fractures significantly increased (p < 0.001), number of surgeries significantly increased (p < 0.000) and number of ORIF treatments significantly increased (p < 0.0004). Addition of 3D imaging of proximal humeral fractures significantly increases number of surgical decisions when compared to radiographs alone or together with CT.

Ly9 (SLAMF3) receptor differentially regulates iNKT cell development and activation in mice.

Invariant natural killer T (iNKT) cells develop into three subsets (NKT1, NKT2, and NKT17) expressing a distinct transcription factor profile, which regulates cytokine secretion upon activation. iNKT cell development in the thymus is modulated by signaling lymphocytic activation molecule family (SLAMF) receptors. In contrast to other SLAMF members, Ly9 (SLAMF3) is a non-redundant negative regulator of iNKT cell development. Here, we show that Ly9 influences iNKT cell lineage differentiation. Ly9-deficient mice on a BALB/c background contained a significantly expanded population of thymic NKT2 cells, while NKT1 cells were nearly absent in BALB/c.Ly9-/- thymus. Conversely, the number of peripheral NKT1 cells in BALB/c.Ly9-/- mice was comparable to that in wild-type mice, indicating that the homeostasis of the different iNKT cell subsets may have distinct requirements depending on their tissue localization. Importantly, Ly9 absence also promoted NKT2 cell differentiation in the NKT1-skewed C57BL/6 background. Furthermore, treatment of wild-type mice with an agonistic monoclonal antibody directed against Ly9 impaired IL-4 and IFN-γ production and reduced by half the number of spleen iNKT cells, with a significant decrease in the proportion of NKT2 cells. Thus, anti-Ly9 targeting could represent a novel therapeutic approach to modulate iNKT cell numbers and activation.

Targeting of Ly9 (CD229) Disrupts Marginal Zone and B1 B Cell Homeostasis and Antibody Responses.

Marginal zone (MZ) and B1 B cells have the capacity to respond to foreign Ags more rapidly than conventional B cells, providing early immune responses to blood-borne pathogens. Ly9 (CD229, SLAMF3), a member of the signaling lymphocytic activation molecule family receptors, has been implicated in the development and function of innate T lymphocytes. In this article, we provide evidence that in Ly9-deficient mice splenic transitional 1, MZ, and B1a B cells are markedly expanded, whereas development of B lymphocytes in bone marrow is unaltered. Consistent with an increased number of these B cell subsets, we detected elevated levels of IgG3 natural Abs and a striking increase of T-independent type II Abs after immunization with 2,4,6-trinitrophenyl-Ficoll in the serum of Ly9-deficient mice. The notion that Ly9 could be a negative regulator of innate-like B cell responses was supported by the observation that administering an mAb directed against Ly9 to wild-type mice selectively eliminated splenic MZ B cells and significantly reduced the numbers of B1 and transitional 1 B cells. In addition, Ly9 mAb dramatically diminished in vivo humoral responses and caused a selective downregulation of the CD19/CD21/CD81 complex on B cells and concomitantly an impaired B cell survival and activation in an Fc-independent manner. We conclude that altered signaling caused by the absence of Ly9 or induced by anti-Ly9 may negatively regulate development and function of innate-like B cells by modulating B cell activation thresholds. The results suggest that Ly9 could serve as a novel target for the treatment of B cell-related diseases.

Sarcoma de Kaposi de pabellón auricular / Kaposi sarcoma in the external ear

No disponible

Ly9 (CD229) Cell-Surface Receptor is Crucial for the Development of Spontaneous Autoantibody Production to Nuclear Antigens.

The Signaling Lymphocyte Activation Molecule Family (SLAMF) genes, which encode cell-surface receptors that modulate innate and adaptive immune responses, lay within a genomic region of human and mouse chromosome 1 that confers a predisposition for the development of systemic lupus erythematosus (SLE). Herein, we demonstrate that the SLAMF member Ly9 arises as a novel receptor contributing to the reinforcement of tolerance. Specifically, Ly9-deficient mice spontaneously developed features of systemic autoimmunity such as the production of anti-nuclear antibodies (ANA), -dsDNA, and -nucleosome autoantibodies, independently of genetic background [(B6.129) or (BALB/c.129)]. In aged (10- to 12-month-old) Ly9 (-/-) mice key cell subsets implicated in autoimmunity were expanded, e.g., T follicular helper (Tfh) as well as germinal center (GC) B cells. More importantly, in vitro functional experiments showed that Ly9 acts as an inhibitory receptor of IFN-γ producing CD4(+) T cells. Taken together, our findings reveal that the Ly9 receptor triggers cell intrinsic safeguarding mechanisms to prevent a breach of tolerance, emerging as a new non-redundant inhibitory cell-surface receptor capable of disabling autoantibody responses.