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In addition to susceptibility to infections, conventional primary immunodeficiency disorders (PIDs) and inborn errors of immunity (IEI) can cause immune dysregulation, manifesting as lymphoproliferative and/or autoimmune disease. Autoimmunity can be the prominent phenotype of PIDs and commonly includes cytopenias and rheumatological diseases, such as arthritis, systemic lupus erythematosus (SLE), and Sjogren’s syndrome (SjS). Recent advances in understanding the genetic basis of systemic autoimmune diseases and PIDs suggest an at least partially shared genetic background and therefore common pathogenic mechanisms. Here, we explore the interconnected pathogenic pathways of autoimmunity and primary immunodeficiency, highlighting the mechanisms breaking the different layers of immune tolerance to self-antigens in selected IEI.

Autoimmunity and immunodeficiency were previously considered to be mutually exclusive conditions; however, increased understanding of the complex immune regulatory and signalling mechanisms involved, coupled with the application of genetic analysis, is revealing the complex relationships between primary immunodeficiency syndromes and autoimmune diseases. Single-gene defects can cause rare diseases that predominantly present with autoimmune symptoms. Such genetic defects also predispose individuals to recurrent infections (a hallmark of immunodeficiency) and can cause primary immunodeficiencies, which can also lead to immune dysregulation and autoimmunity. Moreover, risk factors for polygenic rheumatic diseases often exist in the same genes as the mutations that give rise to primary immunodeficiency syndromes. In this Review, various primary immunodeficiency syndromes are presented, along with their pathogenetic mechanisms and relationship to autoimmune diseases, in an effort to increase awareness of immunodeficiencies that occur concurrently with autoimmune diseases and to highlight the need to initiate appropriate genetic tests. The growing knowledge of various genetically determined pathologic mechanisms in patients with immunodeficiencies who have autoimmune symptoms opens up new avenues for personalized molecular therapies that could potentially treat immunodeficiency and autoimmunity at the same time, and that could be further explored in the context of autoimmune rheumatic diseases.

There have been concerns about high rates of thus far undiagnosed SARS-CoV-2 infections in the health-care system. The COVID-19 Contact (CoCo) Study follows 217 frontline health-care professionals at a university hospital with weekly SARS-CoV-2-specific serology (IgA/IgG). Study participants estimated their personal likelihood of having had a SARS-CoV-2 infection with a mean of 21% [median 15%, interquartile range (IQR) 5–30%]. In contrast, anti-SARS-CoV-2 IgG prevalence was about 1–2% at baseline. Regular anti-SARS-CoV-2 IgG testing of health-care professionals may aid in directing resources for protective measures and care of COVID-19 patients in the long run.

The constant emergence of SARS-CoV-2 variants and sublineages that evade control by neutralising antibodies induced upon infection, vaccination, or both requires the use of adapted vaccines. [...]on July 3, 2024, the European Medicines Agency (EMA) granted market authorisation for a monovalent COVID-19 mRNA vaccine based on the spike protein of JN.1.4 However, immune response data in humans or real-world evidence on vaccine-induced protection are pending. Before JN.1 immunisation, participants showed a median of 2217·0 antibody-binding units per mL (IQR 2709·0) of anti-spike IgG antibodies and a median of 338·0 relative units per mL (IQR 348·5) of omicron IgG antibodies (figure A), which was about twice as high as immune responses before the omicron-directed vaccination against XBB.1.5 we had previously observed.5 The omicron JN.1 vaccination resulted in a significant 1·2-fold increase of anti-spike IgG and 1·2-fold increase of omicron anti-spike IgG (p<0·0001; figure A). After vaccination, the response rates increased significantly for all pseudoviruses except XBB.1·5pp and KP.3pp (figure C; appendix p 10). [...]we observed a significant increase in neutralisation of JN.1pp (median change 2·2-fold), KP.2pp (3·8-fold), KP.2·3pp (3·3-fold), and LB.1pp (4·9-fold).

In gout, crystallization of uric acid in the form of monosodium urate (MSU) leads to a painful inflammatory response. MSU crystals induce inflammation by activating the complement system and various immune cell types, and by inducing necrotic cell death. We previously found that the soluble pattern recognition molecule C-reactive protein (CRP) recognizes MSU crystals, while enhancing complement activation. In the absence of CRP, MSU crystals still induced complement activation, suggesting additional CRP-independent mechanisms of complement activation. In the present study, we searched for additional MSU crystal-binding complement activators. We found that all healthy individuals, even unborn children, have MSU crystal-specific immunoglobulin M (IgM) in their blood. This indicates that innate IgM, also known as natural IgM, recognizes these crystals. In serum lacking IgM and CRP, MSU crystals showed negligible complement activation as assessed by the production of the anaphylatoxins C4a, C3a, and C5a (listed in order of production via the classical complement pathway). We show that IgM and CRP both activate the classical complement pathway on MSU crystals. CRP was more efficient at fixating active C1 on the crystals and inducing release of the most inflammatory anaphylatoxin C5a, indicating non-redundant functions of CRP. Notably, while CRP recognizes MSU crystals but not the related calcium pyrophosphate dihydrate (CPPD) crystals, natural IgM bound to both, suggesting common and distinct mechanisms of recognition of individual crystal types by complement activators.

BackgroundThis study addresses the challenging characterisation and differentiation of CIDP versus CIDP in association with Sjögren’s syndrome to facilitate the process in clinical routine.MethodsPatients with both CIDP and Sjögren’s syndrome and CIDP without Sjögren’s syndrome were compared concerning relevant differences in clinical, laboratory and electrophysiological findings. 154 patients who fulfilled the diagnostic EFNS/PNS criteria for CIDP were included in the analysis. 54 of these patients additionally fulfilled the ACR/EULAR classification criteria for Sjögren’s syndrome.ResultsThe frequency of female patients was higher in patients with CIDP and Sjögren’s syndrome (52%) versus CIDP patients without Sjögren’s syndrome (28%). Furthermore, the occurrence of cranial nerve impairment was significantly higher in patients with Sjögren’s syndrome (39% versus 14%). There were no significant group differences in the evaluation of initial symptoms, severity of disability judged by INCAT disability scale score, presence or distribution of sensory deficits, limb weakness and the presence of ataxia, pain or dysautonomia, CSF laboratory or electrophysiological findings. ConclusionsIn conclusion, our data indicate that cranial nerve impairment and female gender might represent red flags for an additional Sjögren’s syndrome in patients with CIDP. The patterns of clinical disabilities and electrophysiological findings due to peripheral nerve damage are similar in both CIDP entities.

Sjögren's syndrome is a heterogeneous inflammatory disorder frequently involving peripheral nerves with a wide spectrum of sensory modalities and distribution patterns. The objective of this cross-sectional study was to determine characteristics of Sjögren's syndrome as a cause for severe neuropathy with limb weakness. One hundred and eighty four patients with polyneuropathy associated with limb weakness underwent routine diagnostics including investigations for Sjögren's syndrome. Forty-four patients with Sjögren's syndrome (ACR-EULAR classification criteria) and severe neuropathy were identified. Sjögren's syndrome was found at a median age of 63 years and the gender distribution showed a balanced female-male ratio of 1:1. Anti-SSA(Ro) antibodies were detected in 48% while seronegative patients were diagnosed with Sjögren's syndrome based on sialadenitis on minor salivary gland biopsy with a focus score ≥1. The majority of patients (93%) were diagnosed with Sjögren's syndrome after neurological symptoms appeared. Limbs were symmetrically involved in 84% of patients (57% tetraparesis, 27% paraparesis). Sensory function was not affected in 11% of patients indicating that Sjögren's syndrome associated neuropathy can present as a pure motor syndrome. Electrophysiological measurements did not reveal pathognomonic findings (23% demyelinating pattern, 36% axonal pattern, 41% both demyelinating and axonal damage signs). More than half of our patients fulfilled the European Federation of Neurological Societies (EFNS) diagnostic criteria for CIDP indicating that distinction between Neuro-Sjögren and other causes of neuropathy such as CIDP is challenging. Our findings show that severe neuropathy with limb weakness is often associated with Sjögren's syndrome. This is of great importance in identifying and understanding the causes of immune mediated polyneuropathy.

Parkinson's disease (PD) is associated with abnormal hypersynchronicity in basal ganglia-thalamo-cortical loops. The clinical effectiveness of subthalamic nucleus (STN) high frequency stimulation indicates a crucial role of this nucleus within the affected motor networks in PD. Here we investigate alterations in the functional connectivity (FC) profile of the STN using resting state BOLD correlations on a voxel-by-voxel basis in functional magnetic resonance imaging (fMRI). We compared early stage PD patients (n=31) during the medication-off state with healthy controls (n=44). The analysis revealed increased FC between the STN and cortical motor areas (BA 4 and 6) in PD patients in accordance with electrophysiological studies. Moreover, FC analysis of the primary motor cortex (M1) hand area revealed that the FC increase was primarily found in the STN area within the basal ganglia. These findings are in good agreement with recent experimental data, suggesting that an increased STN–motor cortex synchronicity mediated via the so called hyperdirect motor cortex–subthalamic pathway might play a fundamental role in the pathophysiology of PD. An additional subgroup analysis was performed according to the presence (n=16) or absence (n=15) of tremor in patients. Compared to healthy controls tremor patients showed increased STN FC specifically in the hand area of M1 and the primary sensory cortex. In non-tremor patients, increased FC values were also found between the STN and midline cortical motor areas including the SMA. Taken together our results underline the importance of the STN as a key node for the modulation of BG-cortical motor network activity in PD patients. ► STN-motor cortex BOLD-FC is increased in PD. ► Results are a likely correlate of increased STN-M1 β-coherence observed in PD. ► Rigor and tremor appear to be associated with changes in STN-M1 hand area FC. ► Results agree with postulated overactivity in a “hyperdirect” M1-STN pathway.

ObjectiveTo evaluate multiple-ascending doses of enpatoran, a selective toll-like receptor 7/8 (TLR7/8) inhibitor with the potential to modulate processes central to lupus pathophysiology, in patients with systemic and cutaneous lupus erythematosus (SLE/CLE).MethodsIn this randomised, double-blind, placebo-controlled phase Ib trial (NCT04647708), patients with active SLE/CLE were randomised 3:1 to enpatoran or placebo across four cohorts. Treatment duration was 12/24 weeks. All patients had a 2-week safety follow-up. The primary endpoint was safety and tolerability. Secondary endpoints included pharmacokinetics (PK) and clinical response. Change in lupus biomarkers, including interferon gene signature (IFN-GS), was an exploratory endpoint.Results25 patients received placebo (n=6) or enpatoran (n=19); 80% were female, all were white, and the median age was 44 years. By week 12, treatment-emergent adverse events (TEAEs) were reported by 42% of patients across the four enpatoran dose groups and 33% of placebo-treated patients. Enpatoran remained well tolerated to week 24. Most TEAEs (96%) were mild or moderate in severity. There were no serious TEAEs. Enpatoran PK was dose proportional, with peak concentration reached 1–2 hours postdose and an apparent half-life of 6–10 hours across doses. Greater reductions in Systemic Lupus Erythematosus Disease Activity Index 2000, Physician’s Global Assessment and 28-joint count were observed at week 24 with enpatoran versus placebo. Rapid, dose-dependent and reversible suppression of IFN-GS was observed.ConclusionsEnpatoran was well tolerated and demonstrated favourable safety and PK profiles in patients with SLE and CLE. Although preliminary, the SLE disease activity and biomarker results support the therapeutic targeting of TLR7/8 for lupus.Trial registration numberNCT04647708.

The aim of the present study was to investigate the clinical spectrum of IgG subclass deficiencies (IgGSDs) and assess the relative clinical significance of diagnosing each specific IgGSD disorder as compared to the common variable immunodeficiency (CVID). The clinical spectrum and immunological findings from 96 patients, diagnosed with diverse IgGSDs, were retrospectively evaluated. Specific IgGSDs were compared with each other and a cohort of 270 patients with CVID. In comparison to CVID, recurrent lower respiratory tract infections (LRTIs) and bronchiectasis were rarer in IgGSDs, while recurrent mucocutaneous herpes simplex virus reactivations were more common. With respect to autoimmunity, IgGSDs were associated with arthritis, while autoimmune cytopenias were less frequently observed than in CVID. Among IgGSDs, herpes zoster was more common in IgG3SD. Arthritis was more prevalent in IgG1 + 3SD. Given its association with LRTI, splenomegaly, immune thrombocytopenic purpura, and the lower class-switched memory B-cell counts, IgG2 + 4SD is the IgGSD that rather resembles CVID. Comparative evaluation of phenotypes and treatments of patients with IgGSDs and CVID reveals distinct features, suggesting the differential clinical significance of diagnosing IgGSDs. The differential clinical expressions of IgGSDs highlight the need for studying each IgGSD separately in order to optimize disorder-specific follow-up procedures and prophylactic anti-infective measures.