Immunological tolerance to muscle autoantigens involves peripheral deletion of autoreactive CD8+ T cells

Receptor Activator of NF-κB Orchestrates Activation of Antiviral Memory CD8 T Cells in the Spleen Marginal Zone

The spleen plays an important role in protective immunity to bloodborne pathogens. Macrophages and dendritic cells (DCs) in the spleen marginal zone capture microbial antigens to trigger adaptive immune responses. Marginal zone macrophages (MZMs) can also act as a replicative niche for intracellular pathogens, providing a platform for mounting the immune response. Here, we describe a role for RANK in the coordinated function of antigen-presenting cells in the spleen marginal zone and triggering anti-viral immunity. Targeted deletion of RANK results in the selective loss of CD169⁺ MZMs, which provide a niche for viral replication, while RANK signaling in DCs promotes the recruitment and activation of anti-viral memory CD8 T cells. These studies reveal a role for the RANKL/RANK signaling axis in the orchestration of protective immune responses in the spleen marginal zone that has important implications for the host response to viral infection and induction of acquired immunity.

Immune checkpoint failures in inflammatory myopathies: An overview

Dermatomyositis (DM), polymyositis (PM), inclusion body myositis (IBM), immune mediated necrotizing myopathy (IMNM) and overlap myositis (OM) are classified as inflammatory myopathies (IM) with involvement of autoimmune features such as autoreactive lymphocytes and autoantibodies. Autoimmunity can be defined as a loss in self-tolerance and attack of autoantigens by the immune system. Self-tolerance is achieved by a group of immune mechanisms occurring in central and periphal lymphoid organs and tissues, called immune checkpoints, that work in synergy to protect the body from harmful immune reactions. Autoimmune disorders appear when immune checkpoints fail. In this review, the different immune checkpoint failures are discussed in DM, PM, IBM and IMNM. Exploring research contribution in each of these immune checkpoints might help to highlight research perspectives in the field and obtain a more complete picture of IM disease pathology.

Progressive hypoventilation due to mixed CD8+ and CD4+ lymphocytic polymyositis following tremelimumab - durvalumab treatment

BACKGROUND

The combination of CTLA-4 and PD-L1 inhibitors has a manageable adverse effect profile, although rare immune-related adverse events (irAE) can occur.

CASE PRESENTATION

We describe an autoimmune polymyositis following a partial response to combination tremelimumab and durvalumab for the treatment of recurrent lung adenocarcinoma. Radiography revealed significant reduction in all metastases; however, the patient developed progressive neuromuscular hypoventilation due to lymphocytic destruction of the diaphragmatic musculature. Serologic testing revealed a low level of de novo circulating antibodies against striated muscle fiber. Immunohistochemistry revealed type II muscle fiber atrophy with a mixed CD8+ and CD4+ lymphocyte infiltrate, indicative of inflammatory myopathy.

CONCLUSIONS

This case supports the hypothesis that muscle tissue is a target for lymphocytic infiltration in immune checkpoint inhibitor-associated polymyositis. Further insights into the autoimmune mechanism of PM will hopefully contribute to the prevention and treatment of this phenomenon.

Oral-tolerization Prevents Immune Responses and Improves Transgene Persistence Following Gene Transfer Mediated by Adeno-associated Viral Vector

Gene therapy represents a feasible strategy to treat inherited monogenic diseases and intramuscular (i.m.) injection of recombinant adeno-associated viral (AAV) vector is now recognized as a convenient and safe method of gene transfer. However, this approach is hampered by immune responses directed against the vector and against the transgenic protein. We used here to reproduce this situation a mouse model where robust immune responses are induced following injection of an AAV vector coding for an immunogenic transgenic protein. We show that prophylactic oral administration of the immunogenic protein before AAV-mediated gene transfer completely prevented antibody formation and cytotoxic CD8(+) T-cell response. Consistently, prophylactic oral-tolerization considerably improved long-term transgene persistence and expression. Mechanistically, inhibition of the cytotoxic immune response involved abortive proliferation of antigen-specific cytotoxic CD8(+) T cells, upregulation of the PD-1 immunoregulatory molecule, downregulation of the Bcl-2 antiapoptotic factor, and their deletion in the context of AAV-mediated gene transfer. Hence, gene therapy may represent an ideal situation where oral-tolerization can be adopted before or at the same time as vector injection to efficiently prevent deleterious immune responses directed against the transgenic protein.

Autoimmune vitiligo does not require the ongoing priming of naive CD8 T cells for disease progression or associated protection against melanoma

Vitiligo is a CD8 T cell-mediated autoimmune disease that has been shown to promote the longevity of memory T cell responses to melanoma. However, mechanisms whereby melanocyte/melanoma Ag-specific T cell responses are perpetuated in the context of vitiligo are not well understood. These studies investigate the possible phenomenon of naive T cell priming in hosts with melanoma-initiated, self-perpetuating, autoimmune vitiligo. Using naive pmel (gp10025-33-specific) transgenic CD8 T cells, we demonstrate that autoimmune melanocyte destruction induces naive T cell proliferation in skin-draining lymph nodes, in an Ag-dependent fashion. These pmel T cells upregulate expression of CD44, P-selectin ligand, and granzyme B. However, they do not downregulate CD62L, nor do they acquire the ability to produce IFN-γ, indicating a lack of functional priming. Accordingly, adult thymectomized mice exhibit no reduction in the severity or kinetics of depigmentation or long-lived protection against melanoma, indicating that the continual priming of naive T cells is not required for vitiligo or its associated antitumor immunity. Despite this, depletion of CD4 T cells during the course of vitiligo rescues the priming of naive pmel T cells that are capable of producing IFN-γ and persisting as memory, suggesting an ongoing and dominant mechanism of suppression by regulatory T cells. This work reveals the complex regulation of self-reactive CD8 T cells in vitiligo and demonstrates the overall poorly immunogenic nature of this autoimmune disease setting.

Overexpression of MHC class I in muscle of lymphocyte-deficient mice causes a severe myopathy with induction of the unfolded protein response

Muscle fibers do not normally express major histocompatibility complex class I (MHC-I) molecules, and their reexpression is a hallmark of inflammatory myopathies. It has been shown in mice that overexpression of MHC-I induces a poorly inflammatory myositis accompanied by the unfolded protein response (UPR), but it is unclear whether it is attributable to T-cell-mediated MHC-I-dependent immune responses or to MHC-I forced expression per se. Indeed, besides presenting antigenic peptides to CD8(+) T cells, MHC-I may also possibly exert nonimmunologic, yet poorly understood pathogenic effects. Thus, we investigated the pathogenicity of MHC-I expression in muscle independently of its immune functions. HT transgenic mice that conditionally overexpress H-2K(b) in muscle were bred to an immunodeficient Rag2(-/-) background. The muscle proteome was analyzed by label-free high-resolution protein quantitation and Western blot. Despite the absence of adaptive immunity, HT Rag2(-/-) mice developed a very severe myopathy associated with the cytoplasmic accumulation of H-2K(b) molecules. The UPR was manifest by up-regulation of characteristic proteins. In humans, we found that HLA class I molecules not only were expressed at the sarcolemma but also could accumulate intracellularly in some patients with inclusion body myositis. Accordingly, the UPR was triggered as a function of the degree of HLA accumulation in myofibers. Hence, reexpression of MHC-I in normally negative myofibers exerts pathogenic effects independently of its immune function.