BTLA Expression and Function Are Impaired on SLE B Cells

Stimulation of Immune Checkpoint Molecule B and T-Lymphocyte Attenuator Alleviates Experimental Crescentic Glomerulonephritis

SIGNIFICANCE STATEMENT

Treatment of acute, crescentic glomerulonephritis (GN) consists of unspecific and potentially toxic immunosuppression. T cells are central in the pathogenesis of GN, and various checkpoint molecules control their activation. The immune checkpoint molecule B and T-lymphocyte attenuator (BTLA) has shown potential for restraining inflammation in other T-cell-mediated disease models. To investigate its role in GN in a murine model of crescentic nephritis, the authors induced nephrotoxic nephritis in BTLA-deficient mice and wild-type mice. They found that BTLA has a renoprotective role through suppression of local Th1-driven inflammation and expansion of T regulatory cells and that administration of an agonistic anti-BTLA antibody attenuated experimental GN. These findings suggest that antibody-based modulation of BTLA may represent a treatment strategy in human glomerular disease.

BACKGROUND

Modulating T-lymphocytes represents a promising targeted therapeutic option for glomerulonephritis (GN) because these cells mediate damage in various experimental and human GN types. The immune checkpoint molecule B and T-lymphocyte attenuator (BTLA) has shown its potential to restrain inflammation in other T-cell-mediated disease models. Its role in GN, however, has not been investigated.

METHODS

We induced nephrotoxic nephritis (NTN), a mouse model of crescentic GN, in Btla -deficient ( BtlaKO ) mice and wild-type littermate controls and assessed disease severity using functional and histologic parameters at different time points after disease induction. Immunologic changes were comprehensively evaluated by flow cytometry, RNA sequencing, and in vitro assays for dendritic cell and T-cell function. Transfer experiments into Rag1KO mice confirmed the observed in vitro findings. In addition, we evaluated the potential of an agonistic anti-BTLA antibody to treat NTN in vivo .

RESULTS

The BtlaKO mice developed aggravated NTN, driven by an increase of infiltrating renal Th1 cells. Single-cell RNA sequencing showed increased renal T-cell activation and positive regulation of the immune response. Although BTLA-deficient regulatory T cells (Tregs) exhibited preserved suppressive function in vitro and in vivo , BtlaKO T effector cells evaded Treg suppression. Administration of an agonistic anti-BTLA antibody robustly attenuated NTN by suppressing nephritogenic T effector cells and promoting Treg expansion.

CONCLUSIONS

In a model of crescentic GN, BTLA signaling effectively restrained nephritogenic Th1 cells and promoted regulatory T cells. Suppression of T-cell-mediated inflammation by BTLA stimulation may prove relevant for a broad range of conditions involving acute GN.

Autoimmunity and Carcinogenesis: Their Relationship under the Umbrella of Autophagy

The immune system and autophagy share a functional relationship. Both innate and adaptive immune responses involve autophagy and, depending on the disease’s origin and pathophysiology, it may have a detrimental or positive role on autoimmune disorders. As a “double-edged sword” in tumors, autophagy can either facilitate or impede tumor growth. The autophagy regulatory network that influences tumor progression and treatment resistance is dependent on cell and tissue types and tumor stages. The connection between autoimmunity and carcinogenesis has not been sufficiently explored in past studies. As a crucial mechanism between the two phenomena, autophagy may play a substantial role, though the specifics remain unclear. Several autophagy modifiers have demonstrated beneficial effects in models of autoimmune disease, emphasizing their therapeutic potential as treatments for autoimmune disorders. The function of autophagy in the tumor microenvironment and immune cells is the subject of intensive study. The objective of this review is to investigate the role of autophagy in the simultaneous genesis of autoimmunity and malignancy, shedding light on both sides of the issue. We believe our work will assist in the organization of current understanding in the field and promote additional research on this urgent and crucial topic.

New insights in systemic lupus erythematosus: From regulatory T cells to CAR-T-cell strategies

Systemic lupus erythematous is a heterogeneous autoimmune disease with potentially multiorgan damage. Its complex etiopathogenesis involves genetic, environmental, and hormonal factors, leading to a loss of self-tolerance with autoantibody production and immune complex formation. Given the relevance of autoreactive B lymphocytes, several therapeutic approaches have been made targeting these cells. However, the disease remains incurable, reflecting an unmet need for effective strategies. Novel therapeutic concepts have been investigated to provide more specific and sustainable disease modification compared with continued immunosuppression. Autologous hematopoietic stem cell transplantation has already provided the proof-of-concept that immunodepletion can lead to durable treatment-free remissions, albeit with significant treatment-related toxicity. In the future, chimeric antigen receptor-T-cell therapies, for example, CD19 chimeric antigen receptor-T, may provide a more effective lymphodepletion and with less toxicity than autologous hematopoietic stem cell transplantation. An emerging field is to enhance immune tolerance by exploiting the suppressive capacities of regulatory T cells, which are dysfunctional in patients with systemic lupus erythematous, and thus resemble promising candidates for adoptive cell therapy. Different approaches have been developed in this area, from polyclonal to genetically engineered regulatory T cells. In this article, we discuss the current evidence and future directions of cellular therapies for the treatment of systemic lupus erythematous, including hematopoietic stem cell transplantation and advanced regulatory T-cell-based cellular therapies.

The role of immune regulatory molecules in rheumatoid arthritis: Implication for etiopathogenesis and prospective for treatment

Rheumatoid arthritis (RA) is considered an autoimmune chronic disorder and the most common inflammatory arthropathy. Disease progression in RA begins with asymptomatic autoimmune responses in cases with a genetic or environmental predisposition, that alters to arthralgia phase as autoantibodies reach the joints and subjects begin demonstrating nonspecific musculoskeletal presentations lacking any clinical symptoms of synovial inflammation. After that, patients' symptoms develop to undifferentiated arthritis (UA)/idiopathic arthritis (IA) whenever the subjects progress to clinical synovitis systemic comorbidities affecting the vasculature, metabolism, and bone, and eventually with augmented immune cell infiltration, IA/UA patients progress to clinically classifiable RA. RA is mainly correlated with different immune cells and each of them contributes variously to the pathogenesis of the disease. The pathogenesis of RA is altered by the contribution of both T and B cells in an autoimmune irregularity. Modulation of the immune responses occurs through regulatory and inhibitory molecules that control activation of the adaptive system as well as immune hemostasis. To confine the exorbitant T cell-associated inflammatory reactions, the immune system provides a system of inhibitory feedbacks, collectively named immune checkpoints. In this review, we aimed to discuss about inhibitory members of immune checkpoint molecules, including programmed cell death 1 (PD-1)/PD-L1, cytotoxic-T-lymphocyte-antigen-4, lymphocyte activation gene-3, T cell immunoglobulin-3, V-domain Ig suppressor of T cell activation, B- and T-lymphocyte attenuator, and T cell immunoglobulin and ITIM domain and their role in RA.

Autoimmunity and Cancer-Two Sides of the Same Coin

Autoimmune disease results from the immune response against self-antigens, while cancer develops when the immune system does not respond to malignant cells. Thus, for years, autoimmunity and cancer have been considered as two separate fields of research that do not have a lot in common. However, the discovery of immune checkpoints and the development of anti-cancer drugs targeting PD-1 (programmed cell death receptor 1) and CTLA-4 (cytotoxic T lymphocyte antigen 4) pathways proved that studying autoimmune diseases can be extremely helpful in the development of novel anti-cancer drugs. Therefore, autoimmunity and cancer seem to be just two sides of the same coin. In the current review, we broadly discuss how various regulatory cell populations, effector molecules, genetic predisposition, and environmental factors contribute to the loss of self-tolerance in autoimmunity or tolerance induction to cancer. With the current paper, we also aim to convince the readers that the pathways involved in cancer and autoimmune disease development consist of similar molecular players working in opposite directions. Therefore, a deep understanding of the two sides of immune tolerance is crucial for the proper designing of novel and selective immunotherapies.

Antigen-experienced CXCR5- CD19low B cells are plasmablast precursors expanded in SLE

OBJECTIVES

Altered composition of the B cell compartment in the pathogenesis of systemic lupus erythematosus (SLE) is characterized by expanded plasmablast (PB) and IgD^- CD27^- double negative (DN) B cell populations. Previous studies showed that DN B cells represent a heterogeneous subset and further characterization is needed.

METHODS

Therefore, we analyzed two independent cohorts of healthy donors and SLE patients using a combined approach of flow (HD: n=16; SLE: n=28,) and mass cytometry (HD: n=18; SLE: n=24) and targeted RNA sequencing. To study B cell subsets formation in acute immune response versus autoimmunity we investigated HDs at various time points upon vaccination with BNT162b2 or during acute COVID-19 infection using flow cytometry.

RESULTS

We have found that IgD^- CD27⁺ switched and atypical IgD^- CD27^- memory B cells, which are increased in SLE, represent heterogeneous populations composed of three different subsets each. Populations of CXCR5⁺ CD19^int , CXCR5^- CD19^high and CXCR5^- CD19^low are found in both compartments suggesting their relationship. We characterize a hitherto unknown and antigen-experienced CXCR5^- CD19^low subset enhanced in SLE carrying a PB phenotype with diminished B cell receptor responsiveness and expression of CD38, CD95, CD71, PRDM1, XBP-1, and IRF4. CXCR5^- CD19^low subsets are increased and correlate with PB frequencies in SLE and upon BNT162b2-vaccination of HD suggesting their interrelationship and contribution to plasmacytosis. The demonstration of CXCR5^- CD19^low B cells amongst both CD27+ and CD27- cells questions the role of CD27 as reliable marker for B cell differentiation.

CONCLUSION

Our data suggest that CXCR5^- CD19^low B cells are precursors of plasmablasts, thus co-targeting this subset may have therapeutic value in SLE.

[B lymphocytes and plasma cells as drivers of rheumatic diseases]

Verschiedene Arbeitsgruppen am Deutschen Rheuma-Forschungszentrum Berlin haben in enger Zusammenarbeit mit der Medizinischen Klinik mit Schwerpunkt Rheumatologie und Klinische Immunologie an der Charité wichtige Beiträge zur Bedeutung der B‑Zellen und Plasmazellen bei rheumatischen Erkrankungen geleistet, die nicht nur für die Rheumatologie, sondern für alle klinischen Fachgebiete, in denen antikörpervermittelte Erkrankungen eine Rolle spielen, relevant sind. Insbesondere wird auf die gestörte B‑Zell-Homöostase, die Bedeutung des Immunglobulin M(IgM)-Fc-Rezeptors für die Regulation der Autoimmunität, die Rolle der langlebigen Gedächtnis-Plasmazelle bei der Aufrechterhaltung der Autoimmunität sowie die Sicherung ihres Überlebens in speziellen, von Stromazellen organisierten Nischen im Knochenmark und in entzündeten Geweben eingegangen. Die Forschungsergebnisse haben zu einem besseren Verständnis der immunologischen und molekularen Mechanismen bei rheumatischen Erkrankungen und ihrer Therapie beigetragen. Die Identifizierung der langlebigen Gedächtnis-Plasmazelle hat zu vielversprechenden therapeutischen Ansätzen mit kurativem Potenzial bei Autoimmunerkrankungen geführt.

B cells in systemic lupus erythematosus

PURPOSE OF REVIEW

New insight into altered B cell distribution including newly identified subsets and abnormalities in systemic lupus erythematosus (SLE) as well as their role in immune protection are summarized in this review.

RECENT FINDINGS

SLE carries characteristic B cell abnormalities, which offer new insights into B cell differentiation and their disturbances including discoveries of pathogenic B cell subsets and intrinsic B cell abnormalities. A recent study in SLE found that antigen-experienced B cell subsets lacking expression of CD27 and IgD defined by their lack of CXCR5 and CD19low expression are expanded in SLE and represent plasmablasts likely escaping proper selection. In terms of therapeutic targeting with broader coverage than rituximab, second-generation anti-CD20, anti-CD38 and CD19-CART treatment experiences have advanced our understanding recently. However, the key role of qualitative and quantitative B cell requirements in connection with T cells became apparent during SARS-Cov2 infection and vaccination, especially in patients with gradual B cell impairments by rituximab, mycophenolate mofetil and cyclophosphamide.

SUMMARY

Identification and characterization relevant B cell subsets together with altered regulatory mechanisms in SLE facilitates new approaches in targeting pathogenic B cells but require consideration of preservation of protection.

Role of inhibitory signaling in peripheral B cell tolerance*

At least 20% of B cells in the periphery expresses an antigen receptor with a degree of self-reactivity. If activated, these autoreactive B cells pose a risk as they can contribute to the development of autoimmune diseases. To prevent their activation, both B cell-intrinsic and extrinsic tolerance mechanisms are in place in healthy individuals. In this review article, I will focus on B cell-intrinsic mechanisms that prevent the activation of autoreactive B cells in the periphery. I will discuss how inhibitory signaling circuits are established in autoreactive B cells, focusing on the Lyn-SHIP-1-SHP-1 axis, how they contribute to peripheral immune tolerance, and how disruptions of these circuits can contribute to the development of autoimmunity.

Immune checkpoints and the multiple faces of B cells in systemic lupus erythematosus

PURPOSE OF REVIEW

B-lymphocytes are crucial in the pathogenesis of systemic lupus erythematosus (SLE), including autoantibody production, antigen presentation, co-stimulation, and cytokine secretion. Co-stimulatory and co-inhibitory molecules control interactions between B and T cells during an inflammatory response, which is essential for an appropriate host protection and maintenance of self-tolerance. Here, we review recent findings about checkpoint molecules and SLE B cells including their potential therapeutic implications and experiences from clinical trials.

RECENT FINDINGS

Most prominent checkpoint molecules involved in pathologic B and T cell interaction in SLE are CD40/CD40L and inducible co-stimulator/ICOSL, both also intimately involved in the formation of germinal centers and ectopic lymphoid tissue. Dysregulations of inhibitory checkpoint molecules, like programmed death-1/programmed death-ligand 1 and B- and T-lymphocyte attenuator have been suggested to impair B cell functions in SLE recently.

SUMMARY

Accumulating evidence indicates that dampening immune responses by either blocking co-activating signals or enhancing co-inhibitory signals in different cell types is a promising approach to treat autoimmune diseases to better control active disease but may also allow resolution of chronic autoimmunity.