Is immunology doing well? A look at 100 immune-mediated inflammatory diseases for 100 years of the Journal.

It is now 60 years since Ian Mackay and Macfarlane Burnet published their seminal text "The Autoimmune Diseases" in which they examined the full scope of human inflammatory pathology as a manifestation of the underlying structure and function of the immune system. Here I revisit this approach to ask to what extent has the promise of Mackay and Burnet's work been exploited in clinical medicine as currently practiced. In other words, is immunology doing well? Despite spectacular headline contributions of immunology in clinical medicine, I present evidence suggesting a performance ceiling in our capacity to answer the relatively straightforward questions that patients frequently ask about their own diseases and find that this ceiling exists across almost all of the 100 immune-mediated inflammatory diseases examined. I propose that these questions are difficult, not so much because the immune system is overwhelmingly complex but rather that we have more to learn about the relatively simple agents and rules that may underpin self-organizing complex interacting systems as revealed in studies from other disciplines. The way that the immune system has evolved to exploit the ancient machinery determining three independent cell fate timers as described in this Journal would be a great place to start to decode the self-organizing principles that underpin the emergent pathology that we observe in the clinic.

Distinguishing CNS neurosarcoidosis from multiple sclerosis and an approach to "overlap" cases.

Neurosarcoidosis is an important diagnosis to exclude in the work-up for suspected multiple sclerosis (MS). The distinction between the two conditions is usually possible due to characteristic clinical manifestations, magnetic resonance imaging (MRI) findings, and the results of other supportive investigations such as CT-PET. Definitive diagnosis can be made by histopathological examination, but this is not always practical. Misdiagnosis can occur when the clinical characteristics and MRI findings of both conditions overlap. Those patients with characteristic findings of MS but extraneural histopathological evidence of sarcoidosis are a particularly difficult diagnostic group. Diagnostic clarity is essential to inform treatment, especially as certain treatments for one disorder can exacerbate the other. This article summarises the clinical, laboratory and radiological findings that aid the clinician in distinguishing between the two conditions. It also discusses the literature on the potential for sarcoidosis and MS to co-exist in some patients, and how to approach the treatment of these "overlap" patients.

The spectrum of immune-mediated and inflammatory lesions of the brainstem: Clues to diagnosis.

The presentation of a patient with brainstem symptoms and signs invokes a number of common and less common differential diagnoses, and accurate diagnosis can be challenging. We review the major immune-mediated and inflammatory syndromes that can affect the brainstem including multiple sclerosis, neuromyelitis optica spectrum disorder, neuro-Behçet disease, chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids, neurosarcoidosis, Susac syndrome, and the histiocytic disorders. We focus on clinical features and MRI clues that help to distinguish among the different brainstem conditions. Accurate diagnosis is important to guide appropriate treatment and limit neurologic disability.

Association between musk antibody concentrations and the myasthenia gravis composite score in 3 patients: A marker of relapse?

INTRODUCTION: Muscle-specific tyrosine kinase (MuSK) autoantibody related myasthenia gravis is characterized by bulbar and respiratory manifestations, a poor response to anticholinergics, and a generally good response to plasma exchange and rituximab. It is not known if MuSK-antibody (Ab) levels could be used to predict the clinical course Methods: Three patients for whom frequent long-term monitoring of MuSK-Ab levels and the Myasthenia Gravis Composite (MGC) scores were performed are described. RESULTS: A close relationship existed between the MuSK-Ab concentrations and the MGC score. Furthermore, a rise in Ab concentration preceded a more serious clinical relapse in all patients Conclusions: These findings suggest that MuSK-Ab concentrations may be a useful biomarker for the long-term monitoring of MuSK myasthenia gravis, particularly while in clinical remission. This may allow preemptive escalation of therapy to prevent clinical relapse, and conversely permitting greater weaning of unnecessary immunosuppression. Muscle Nerve, 2019.

Immune-mediated conditions affecting the brain, eye and ear (BEE syndromes).

The triad of central nervous system symptoms, visual disturbance and hearing impairment is an oft-encountered clinical scenario. A number of immune-mediated diseases should be considered among the differential diagnoses including: Susac syndrome, Cogan syndrome or Vogt-Koyanagi-Harada disease; demyelinating conditions such as multiple sclerosis or neuromyelitis optica spectrum disorder; systemic diseases such as systemic lupus erythematosus, Sjögren syndrome or Behcet disease and granulomatous diseases such as sarcoidosis. In this article, we coin the term 'BEE syndromes' to draw attention to the various immune-mediated diseases that affect the brain, eye and ear. We present common disease manifestations and identify key clinical and investigation features.

A systematic checklist approach to immunosuppression risk management: An audit of practice at two clinical neuroimmunology centers.

There is no consensus approach to safety screening for immune intervention in clinical neuroimmunology. An immunosuppression risk evaluation checklist was used as an audit tool to assess real-world immunosuppression risk management and formulate recommendations for quality improvements in patient safety. Ninety-nine patients from two centres with 27 non-MS diagnoses were included. An average of 1.9 comorbidities with the potential to adversely impact morbidity and mortality associated with immunosuppression were identified. Diabetes and smoking were the most common, however a range of rarer but potentially life-threatening co-morbid disorders in the context of immunosuppression were identified. Inadequate documentation of risk mitigation tasks was common at 40.1% of total tasks across both cohorts. A routine, systematic immunosuppression checklist approach should be considered to improve immunosuppression risk management in clinical neuroimmunology practice.

The corpus callosum in the diagnosis of multiple sclerosis and other CNS demyelinating and inflammatory diseases.

Lesions in the corpus callosum (CC) are important radiological clues to the diagnosis of multiple sclerosis (MS), but may also occur in other neuroinflammatory and non-neuroinflammatory conditions. In this article, we discuss the radiological features of lesions within the CC in MS and other central nervous system inflammatory and acquired demyelinating diseases. An understanding of the appearance and location of lesions in the CC is important not only for accurate diagnosis and treatment of these various conditions, but as it also provides insights into pathogenesis.

Induction intravenous cyclophosphamide followed by maintenance oral immunosuppression in refractory myasthenia gravis.

INTRODUCTION: Myasthenia gravis (MG) can be refractory to conventional immunotherapy. We report on the efficacy and durability of intravenous (IV) remission-induction cyclophosphamide (CYC) followed by oral immunosuppression in refractory MG. METHODS: We identified 8 patients from our medical records with moderate or severe refractory MG who were treated with 6 cycles of IV CYC (0.75 g/m(2) ) every 4 weeks followed by oral immunosuppression. RESULTS: Six patients improved within 3 months of treatment. Four patients remained in clinical remission (mean follow-up 31 months). Two patients responded partially, and 1 patient relapsed after 11 months. Two patients were non-responders. CYC was well tolerated. Acetylcholine receptor antibody levels remained below pretreatment levels in patients in clinical remission. The leukocyte nadir was lower in CYC responders. CONCLUSIONS: Remission-induction IV CYC followed by oral immunosuppression is a rapid, effective, and durable treatment for refractory MG. Adding a post-CYC immunosuppressant may account for low relapse rates compared with other published series.

Muckle-Wells cryopyrinopathy: complex phenotyping and response to therapy in a new multiplex kindred.

Muckle-Wells syndrome (MWS) is a member of the cryopyrin-associated periodic syndrome family of auto-inflammatory diseases, originally described as a triad of urticaria, sensorineural deafness and amyloidosis. IL-1 blockade is a proven therapy for MWS. The clinical, laboratory and genotypic characteristics of a novel kindred of five individuals with Muckle-Wells syndrome are described. Response to IL-1 blockade therapy in the proband was evaluated. All five affected family members experienced symptoms of multi-organ inflammation. Lead time between symptom onset and diagnosis was approximately 30 years in the proband. Fever was not a universal feature in all affected family members. Anti-IL-1 therapy in the proband resulted in improvements in patient-reported symptoms, inflammatory markers, auditory acuity and reversal of her infertility. Muckle-Wells syndrome is a rare, multisystem, auto-inflammatory syndrome. Delay in diagnosis prevents effective treatment. We propose reversal of infertility to be among the potential benefits of IL-1 inhibition in this disease.

Circulating precursor CCR7(lo)PD-1(hi) CXCR5⁺ CD4⁺ T cells indicate Tfh cell activity and promote antibody responses upon antigen reexposure.

Follicular B helper T (Tfh) cells support high affinity and long-term antibody responses. Here we found that within circulating CXCR5⁺ CD4⁺ T cells in humans and mice, the CCR7(lo)PD-1(hi) subset has a partial Tfh effector phenotype, whereas CCR7(hi)PD-1(lo) cells have a resting phenotype. The circulating CCR7(lo)PD-1(hi) subset was indicative of active Tfh differentiation in lymphoid organs and correlated with clinical indices in autoimmune diseases. Thus the CCR7(lo)PD-1(hi) subset provides a biomarker to monitor protective antibody responses during infection or vaccination and pathogenic antibody responses in autoimmune diseases. Differentiation of both CCR7(hi)PD-1(lo) and CCR7(lo)PD-1(hi) subsets required ICOS and BCL6, but not SAP, suggesting that circulating CXCR5⁺ helper T cells are primarily generated before germinal centers. Upon antigen reencounter, CCR7(lo)PD-1(hi) CXCR5⁺ precursors rapidly differentiate into mature Tfh cells to promote antibody responses. Therefore, circulating CCR7(lo)PD-1(hi) CXCR5⁺ CD4⁺ T cells are generated during active Tfh differentiation and represent a new mechanism of immunological early memory.

Autoimmunity in primary antibody deficiency is associated with protein tyrosine phosphatase nonreceptor type 22 (PTPN22).

BACKGROUND: The 1858T allele of protein tyrosine phosphatase nonreceptor type 22 (PTPN22; R620W) exhibits one of the strongest and most consistent associations with sporadic autoimmune disease. Although autoimmunity is common in patients with primary antibody deficiency (PAD), it remains unknown whether its pathogenesis is similar when it arises in this context compared with in immunocompetent patients. OBJECTIVE: We set out to determine whether the 1858T allele of PTPN22 was associated with PAD or with autoimmunity in the context of PAD. METHODS: We genotyped rs2476601 (g.1858C>T), a single nucleotide polymorphism encoding substitution of arginine for tryptophan in PTPN22 (R620W), in 193 patients with PAD and 148 control subjects from an Australian cohort. We also performed a subgroup analysis according to the presence of autoimmunity and B-cell phenotypes. RESULTS: C/T and T/T PTPN22 genotypes were more common in patients with PAD than in the matched control subjects (C/T, 18.1% vs 9.5%; T/T, 1.04% vs 0.6%). The T allele was associated with an increased risk of PAD relative to control subjects (odds ratio, 2.10; 95% CI, 1.11-4.00). The distribution of genotypes in control subjects was similar to those reported previously and did not deviate significantly from Hardy-Weinberg equilibrium. We found a strong association between the 1858T allele and PAD with coexistent autoimmune diseases. In patients with PAD and autoimmunity, 16 (43.2%) of 37 had at least one T allele of PTPN22 compared with 27 (17.3%) of 156 with the C/C genotype (P=.0014; odds ratio, 3.64; 95% CI, 1.68-7.88). We found no evidence that this effect was mediated by enrichment of CD21low B cells. CONCLUSION: The 1858T PTPN22 allele is strongly associated with autoimmunity in patients with PAD.

Expansion of somatically reverted memory CD8+ T cells in patients with X-linked lymphoproliferative disease caused by selective pressure from Epstein-Barr virus.

Patients with the primary immunodeficiency X-linked lymphoproliferative disease (XLP), which is caused by mutations in SH2D1A, are highly susceptible to Epstein-Barr virus (EBV) infection. Nonetheless, some XLP patients demonstrate less severe clinical manifestations after primary infection. SH2D1A encodes the adaptor molecule SLAM-associated protein (SAP), which is expressed in T and natural killer cells and is required for cytotoxicity against B cells, the reservoir for EBV. It is not known why the clinical presentation of XLP is so variable. In this study, we report for the first time the occurrence of somatic reversion in XLP. Reverted SAP-expressing cells resided exclusively within the CD8(+) T cell subset, displayed a CD45RA(-)CCR7(-) effector memory phenotype, and were maintained at a stable level over time. Importantly, revertant CD8(+) SAP(+) T cells, but not SAP(-) cells, proliferated in response to EBV and killed EBV-infected B cells. As somatic reversion correlated with EBV infection, we propose that the virus exerts a selective pressure on the reverted cells, resulting in their expansion in vivo and host protection against ongoing infection.

Molecular pathogenesis of EBV susceptibility in XLP as revealed by analysis of female carriers with heterozygous expression of SAP.

X-linked lymphoproliferative disease (XLP) is a primary immunodeficiency caused by mutations in SH2D1A which encodes SAP. SAP functions in signalling pathways elicited by the SLAM family of leukocyte receptors. A defining feature of XLP is exquisite sensitivity to infection with EBV, a B-lymphotropic virus, but not other viruses. Although previous studies have identified defects in lymphocytes from XLP patients, the unique role of SAP in controlling EBV infection remains unresolved. We describe a novel approach to this question using female XLP carriers who, due to random X-inactivation, contain both SAP(+) and SAP(-) cells. This represents the human equivalent of a mixed bone marrow chimera in mice. While memory CD8(+) T cells specific for CMV and influenza were distributed across SAP(+) and SAP(-) populations, EBV-specific cells were exclusively SAP(+). The preferential recruitment of SAP(+) cells by EBV reflected the tropism of EBV for B cells, and the requirement for SAP expression in CD8(+) T cells for them to respond to Ag-presentation by B cells, but not other cell types. The inability of SAP(-) clones to respond to Ag-presenting B cells was overcome by blocking the SLAM receptors NTB-A and 2B4, while ectopic expression of NTB-A on fibroblasts inhibited cytotoxicity of SAP(-) CD8(+) T cells, thereby demonstrating that SLAM receptors acquire inhibitory function in the absence of SAP. The innovative XLP carrier model allowed us to unravel the mechanisms underlying the unique susceptibility of XLP patients to EBV infection in the absence of a relevant animal model. We found that this reflected the nature of the Ag-presenting cell, rather than EBV itself. Our data also identified a pathological signalling pathway that could be targeted to treat patients with severe EBV infection. This system may allow the study of other human diseases where heterozygous gene expression from random X-chromosome inactivation can be exploited.

Managing the risks of immunosuppression.

PURPOSE OF REVIEW: New immunomodulating approaches to neuroinflammatory diseases present new challenges in clinical risk management. We review recent data on immunosuppression in diverse settings to guide the assessment and prevention of adverse effects from these therapies with the aim of improving the benefit to risk equation. RECENT FINDINGS: Although individual immunomodulatory agents affect the immune system in different ways, there are common themes in patient risk. Impairment of immunity is primarily responsible for an increased risk of a characteristic spectrum of infection-related cancers in immunocompromised patients. Additional themes include the reactivation of existing infections such as herpes viruses, mycobacterial and JC virus infections, vaccine preventable disease, cardiovascular and metabolic risk and immune dysregulation resulting in autoimmune and immune reconstitution inflammatory syndromes. An online immunosuppression screening tool may help reduce omissions in individual patient-specific risk assessment. SUMMARY: Systematic patient-tailored risk management protocols will be required to ensure reduction in preventable adverse outcomes with new immunomodifying approaches to neuroinflammatory disease and thereby optimize the benefits to patients from these treatments.

B cell-intrinsic signaling through IL-21 receptor and STAT3 is required for establishing long-lived antibody responses in humans.

Engagement of cytokine receptors by specific ligands activate Janus kinase-signal transducer and activator of transcription (STAT) signaling pathways. The exact roles of STATs in human lymphocyte behavior remain incompletely defined. Interleukin (IL)-21 activates STAT1 and STAT3 and has emerged as a potent regulator of B cell differentiation. We have studied patients with inactivating mutations in STAT1 or STAT3 to dissect their contribution to B cell function in vivo and in response to IL-21 in vitro. STAT3 mutations dramatically reduced the number of functional, antigen (Ag)-specific memory B cells and abolished the ability of IL-21 to induce naive B cells to differentiate into plasma cells (PCs). This resulted from impaired activation of the molecular machinery required for PC generation. In contrast, STAT1 deficiency had no effect on memory B cell formation in vivo or IL-21-induced immunoglobulin secretion in vitro. Thus, STAT3 plays a critical role in generating effector B cells from naive precursors in humans. STAT3-activating cytokines such as IL-21 thus underpin Ag-specific humoral immune responses and provide a mechanism for the functional antibody deficit in STAT3-deficient patients.

Dermal enhancement: bacterial products on intact skin induce and augment organ-specific autoimmune disease.

The skin is both an essential barrier for host defense and an important organ of immunity. In this study, we show that the application of cholera toxin to intact mouse skin induces and enhances autoimmune diseases affecting organs at distant anatomic sites, whereas its administration by the mucosal route has been reported to have the opposite effect. First, the CNS autoantigen myelin oligodendrocyte glycoprotein 35-55, when applied repeatedly with cholera toxin to the intact skin of healthy C57BL/6 mice, induced relapsing paralysis with demyelinating immunopathologic features similar to multiple sclerosis. Second, the application of cholera toxin in the absence of autoantigen exacerbated the severity of conventional experimental autoimmune encephalomyelitis induced by myelin oligodendrocyte glycoprotein in CFA. Third, the application of cholera toxin to the intact skin of NOD/Lt mice, with or without insulin B peptide 9-23, exacerbated insulitis and T lymphocyte-derived IFN-gamma and IL-4 production in the islets of Langerhans, resulting in an increased incidence and rate of onset of autoimmune diabetes. The data presented in this study highlight the different outcomes of adjuvant administration by different routes. Because dermal application of cholera toxin, and other bacterial products with similar adjuvant activities, is being developed as a clinical vaccination strategy, these data raise the possibility that it could precipitate autoimmune disease in genetically susceptible humans.

Membrane lymphotoxin contributes to anti-leishmanial immunity by controlling structural integrity of lymphoid organs.

Lymphotoxin (LT)alpha in combination with LTbeta forms membrane-bound heterotrimeric complexes with a crucial function in lymph node (LN) organogenesis and correct morphogenesis of secondary lymphoid tissue. To study the role of membrane LT (mLT) in lymphoid tissue organogenesis we generated an LTbeta-deficient mouse strain on a pure genetic C57BL/6 background (B6.LTbeta-/-) and compared it to a unique series of LTalpha-, TNF- and TNF/LTalpha-gene-targeted mice on an identical genetic background (B6.LTalpha-/-, B6.TNF-/- and B6 TNF/LTalpha-/-). B6.LTbeta-/- mice lacked peripheral LN with the exception of mesenteric LN, and displayed a disturbed micro-architecture of the spleen, although less profoundly than LTalpha- or TNF/LTalpha-deficient mice. Radiation bone marrow chimeras (B6.WT-->B6.LTbeta-/- developed Peyer's patch (PP)-like lymphoid aggregates in the intestinal wall indicating a possible role for soluble LTalpha(3) in the formation of the PP anlage. After infection with Leishmania major, B6.LTbeta-/- mice developed a fatal disseminating leishmaniasis resulting in death after 8 to 14 weeks, despite the natural resistance of the C57BL/6 genetic background (B6.WT) mice to the parasite. Both, the cellular and the humoral anti-L. major immune responses were delayed and ineffective. However, the expression pattern of the key cytokines IFN-gamma and IL-12 were comparable in B6.WT and B6.LTbeta-/- mice. Infection of radiation bone marrow chimeras showed that it is the LTbeta-dependent presence of lymphoid tissue and not the expression of mLT itself that renders mice resistant to leishmaniasis.

Gene targeting technology and advances in the pathophysiology of inflammation.

Gene targeting ('knock-out') technology is now widely used in the basic science of all disciplines of pathology and particularly auto-immune and inflammatory disease. Gene targeting is the wilful introduction of precise mutations into the genome of an animal, usually a mouse, affecting the function of a single gene or genes. The phenotyping of knockout mice provides whole animal data on the functions of individual genes in pathophysiological settings, and frequently provides the basis for novel therapeutic strategies. 'Knock-ins', the Cre-LoxP system and conditional knockouts are important new advances. This paper serves as an introduction to the methodology and draws on examples of major advances in inflammation research provided by the targeting of cytokines, in particular the tumour necrosis factor family of ligands.