Adenosine Deaminase 2 Deficiency (DADA2): A Crosstalk Between Innate and Adaptive Immunity

The pathogenesis, clinical presentations and treatment of monogenic systemic vasculitis

Many monogenic autoinflammatory diseases, including DADA2 (deficiency of adenosine deaminase 2), HA20 (haploinsufficiency of A20), SAVI (STING-associated vasculopathy with onset in infancy), COPA syndrome, LAVLI (LYN kinase-associated vasculopathy and liver fibrosis) and VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome, present predominantly with vasculitis and constitute a substantial subgroup of vasculitic conditions associated with a 'probable aetiology'. The spectrum of monogenic vasculitis encompasses all sizes and types of blood vessel, ranging from large vessels to medium-size and small vessels, and from the arterial side to the venous side of the vasculature. Monogenic vasculitis typically starts early in life during infancy or childhood; VEXAS syndrome, which presents in late adulthood, is an exception. The activation of myeloid cells via inflammasome and nuclear factor-κB pathways, type I interferon-enhanced autoimmune mechanisms and/or dysregulated adaptive immune responses have an important role in the development of immune-mediated endothelial dysfunction and vascular damage. Genetic testing is essential for the diagnosis of underlying monogenic autoinflammatory diseases; however, the penetrance of genetic variants can vary. Increased awareness and recognition of distinctive clinical findings could facilitate earlier diagnosis and allow for more-targeted treatments.

Arterial and venous thrombosis in systemic and monogenic vasculitis

Systemic vasculitis, common forms of which include anti-neutrophil cytoplasmic antibody-associated small-vessel vasculitis, large-vessel vasculitis and Behçet syndrome, are frequently complicated by arterial or venous thrombotic events (AVTEs). Newly identified entities such as DADA2 (deficiency of adenosine deaminase 2) and VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome, which are driven by genetic mutations, also exhibit vasculitic features and are associated with a high risk of AVTEs. AVTEs in systemic vasculitis, including monogenic forms of vasculitis, are due to the complex interaction of inflammation and coagulation. New insights into the pathogenetic mechanisms implicate endothelial dysfunction, immune complex deposition and the interplay of pro-inflammatory cytokines with prothrombotic factors, which collectively promote thrombus formation. AVTEs impose a substantial disease burden, complicate diagnosis and negatively affect prognosis by increasing the risk of morbidity and mortality. Early diagnosis and treatment are crucial to prevent lasting damage. Management strategies should target both thrombosis and underlying inflammation. Antithrombotic therapies, including low-dose aspirin, or oral anticoagulants should be used on the basis of individual thrombotic risk assessment. Immunosuppressive therapy is the cornerstone of treatment for arterial and venous thrombosis, particularly in Behçet syndrome, in which vascular inflammation has a crucial role in thrombotic complications.

Unique transcriptomic responses of rat and human alveolar macrophages in an in vitro model of overload with TiO2 and carbon black

BACKGROUND

Chronic inhalation of titanium dioxide or carbon black can lead, at high exposure, to lung overload, and can induce chronic inflammation and lung cancer in rats. Whether this rat adverse response is predictive for humans has been questioned for more than 40 years. Currently, these particles are conservatively considered as possible human carcinogens.

OBJECTIVE

To clarify the mechanisms of the adverse rat response to lung overload and its human relevance.

METHODS

Primary rat and human alveolar macrophages were exposed in vitro to control, non-overload or overload doses of titanium dioxide (P25) or carbon black (Printex 90) particles, and their activation profile was examined by untargeted transcriptomics.

RESULTS

Rat macrophages were largely the most responsive to particle overload. In particular, eighteen genes were identified as robust markers of P25 and Printex 90 overload in rat cells. The known functions of these genes can be related to the potential mechanisms of the adverse outcomes recorded in rats in vivo. Most of these 18 genes were similarly modulated in human macrophages, but with a markedly lower magnitude. In addition, a 16 gene signature was observed upon overload in human macrophages, but not in rat macrophages.

CONCLUSIONS

These findings provide insights into the mechanisms of lung overload and inflammation in rats, and highlight similarities and differences in transcriptomic responses of rat and human alveolar macrophages.

Sequential central retinal artery occlusion in two brothers: a fight to prevent blindness

IMPORTANCE

Central retinal artery occlusion (CRAO) is typically associated with older patients with cardiovascular risk factors. However, its occurrence in younger patients without these risk factors suggests the need to explore rare genetic conditions. Identifying genetic disorders like adenosine deaminase 2 deficiency (DADA2), a vasculitic disease, can be critical in such cases to prevent further complications.

OBJECTIVE

To report the challenging diagnosis of two cases of CRAO in brothers under the age of 40, leading to the diagnosis of DADA2, a rare genetic vasculitic disorder.

RESULTS

A 34-year-old man and his 32-year-old brother, both without significant medical histories, presented with CRAO eight years apart. Extensive diagnostic evaluations, including blood tests, imaging, and autoimmunity panels, failed to identify common causes. Progressive neurological symptoms in the older brother and the similar presentation in his sibling led to further investigation, including genetic testing. A homozygous mutation c.752C > T p.(Pro251Leu) in the CECR1 gene confirmed the diagnosis of DADA2 in both brothers.

CONCLUSION

These cases underscore the importance of considering genetic disorders like DADA2 in young patients presenting with unexplained vascular occlusions. DADA2, characterized by vasculitis, immune dysregulation, and hematologic disorders, can manifest variably, complicating early diagnosis. Effective treatment with TNF inhibitors can prevent further vision loss and mitigate systemic complications. To our knowledge, these are the first reported cases of DADA2 with CRAO as the initial manifestation without prior clinical findings.

Mimics and challenging presentations of DADA2

Deficiency of adenosine deaminase 2 (DADA2) has been a challenging diagnosis to make since it was first described in 2014. The disease represents a wide range of phenotypes. Therefore, it may present with various clinical patterns. Throughout the years, several difficult-to-diagnose cases of DADA2 were reported in the literature. Although several studies and reviews were published regarding different phenotypes and manifestations of DADA2, a review of challenging cases with diverse combinations of DADA2 manifestations was needed to integrate the knowledge from the literature into the clinical practice. Immunological, hematologic, autoinflammatory, and adult-onset polyarteritis-nodosa patterns were reported in the literature as cases challenging to diagnose. In this review, we aim to summarize the challenging case reports from the literature, provide an algorithmic approach for these kinds of presentations, and share our perspective and recommendations on the topic. Diagnosing DADA2 on time is a vital issue for preventing fatal and debilitating vascular events with anti-TNF-alpha therapy. Thus, early testing for DADA2 in suspected cases is recommended. Family history and genetic testing of the patient and the first-degree relatives are essential for accurate diagnosis. Thorough systemic examination and imaging might help detect clinically silent findings of vasculitis. Enzymatic activity of ADA2, when available, is also a key diagnostic tool that complements genetic testing and clinical evaluation.

Adenosine relaxes vagina smooth muscle through the cyclic guanosine monophosphate- and cyclic guanosine monophosphate-dependent pathways

BACKGROUND

In males, adenosine (ADO) is known to relax penile smooth muscles, although its role in the vagina is not yet fully elucidated.

AIM

This study investigated the effect of ADO on vagina smooth muscle activity, using a validated female Sprague-Dawley rat model.

METHODS

Contractility studies, using noradrenaline-precontracted vaginal strips, tested the effects of ADORA1/3 antagonists and ADORA2A/2B antagonists and agonists. Increasing doses of ADO were tested after in vivo or in vitro treatment with Nω-nitro-L-arginine-methyl-ester hydrochloride (L-NAME) or with guanylate or adenylate cyclase inhibitors. Immunopositivity for ADORA2A and ADORA2B was assessed, and messenger RNA (mRNA) analysis was performed. Cyclic ADO monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) were quantified both in rat vagina smooth muscle cells (rvSMCs) and in vaginal tissues with increasing doses of ADO.

OUTCOMES

Demonstrating ADO's role in the relaxing/contractile mechanism in distal vagina smooth muscle.

RESULTS

All ADO receptors mRNAs were expressed in vaginal tissue, with a prevalent content of ADORA2B. A high expression of genes regulating ADO catabolism (ADK) and de novo synthesis (NT5E) was found. In vaginal strips, ADO induced relaxation with IC50 = 144.7 μM and a flat pseudo-Hill coefficient value = -0.42, indicating an activity on heterogeneous receptors. Blocking ADORA1/3 shifted ADO response to the left and with a steeper slope. ADORA2A/2B agonists showed a higher potency than ADO in inducing relaxation. Immunolocalization confirmed the presence of ADORA2A/2B in vaginal musculature, in the blood vessels endothelium, and in the epithelium. ADO stimulation of vagina tissues induced a significant increase in cAMP and cGMP contents. Experiments on rvSMCs confirmed that ADO time- and dose-dependently stimulated cAMP production in these cells. However, ADORA2A/2B antagonists, although reducing the ADO-induced relaxation, did not completely block it. A similar inhibition was obtained by blocking adenylate cyclase. Overall, these findings suggest that ADO relaxation involves other pathways, eg, nitric oxide (NO)/cGMP. Accordingly, blocking NO formation through L-NAME substantially blunted ADO responsiveness, as it does the block of cGMP formation through 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one. Simultaneous incubation with cGMP and cAMP blockers completely inhibited ADO responsiveness.

CLINICAL TRANSLATION

The study highlights ADO's role in regulating vaginal smooth muscle activity, suggesting its potential effect on the vagina.

STRENGTHS AND LIMITATIONS

This is the first study on ADO in the vagina, although the results are preliminary and limited to the rat model.

CONCLUSION

These results show that ADO acts as a vaginal relaxing modulator through selective activation of receptors involving not only cAMP but also cGMP.

Targeting the Type I Interferon Pathway in Glomerular Kidney Disease: Rationale and Therapeutic Opportunities

Type I interferons (IFNs) are immunostimulatory molecules that can activate the innate and adaptive immune systems. In cases of immune dysfunction, prolonged activation of the type I IFN pathway has been correlated with kidney tissue damage in a wide range of kidney disorders, such as lupus nephritis (LN) and focal segmental glomerulosclerosis (FSGS). Genetic mutations, such as APOL1 risk variants in conjunction with elevated type I IFN expression, are also associated with higher rates of chronic kidney disease in patients with LN and collapsing FSGS. Long-term activation of the type I IFN pathway can result in chronic inflammation, leading to kidney tissue damage, cell death, and decline in organ function. Thus, therapeutic strategies targeting type I IFN could provide clinical benefits to patients with immune dysregulation who are at risk of developing impaired kidney function. Here, we present a critical review of type I IFN signaling, the consequences of chronically elevated type I IFN expression, and therapeutic strategies targeting type I IFN signaling in the context of kidney disease.

Adenosine deaminase 2 regulates the activation of the toll-like receptor 9 in response to nucleic acids

Human cells contain two types of adenosine deaminases (ADA) each with unique properties: ADA1, which is present in all cells where it modulates intracellular functions and extracellular signaling, and ADA2, which is secreted by immune cells. The exact intracellular functions of ADA2 remain undetermined and less defined than those of ADA1. ADA2 has distinct characteristics, such as low adenosine affinity, heparin-binding ability, and putative lysosomal entry. Here, we confirm that ADA2 is a lysosomal protein that binds toll-like receptor 9 (TLR9) agonists, specifically CpG oligodeoxynucleotides (CpG ODNs). We show that interferon-alpha (IFN-α) is secreted in response to TLR9 activation by CpG ODNs and natural DNA and markedly increases when ADA2 expression is downregulated in plasmacytoid dendritic cells (pDCs). Additionally, the pretreatment of pDCs with RNA further stimulates IFN-α secretion by pDCs after activation with CpG ODNs. Our findings indicate that ADA2 regulates TLR9 responses to DNA in activated pDCs. In conclusion, decreasing ADA2 expression or blocking it with specific oligonucleotides can enhance IFN-α secretion from pDCs, improving immune responses against intracellular infections and cancer.

Plasma adenosine deaminase-1 and -2 activities are lower at birth in Papua New Guinea than in The Gambia but converge over the first weeks of life

Introduction

Dynamic cellular and molecular adaptations in early life significantly impact health and disease. Upon birth, newborns are immediately challenged by their environment, placing urgent demands on the infant immune system. Adenosine deaminases (ADAs) are enzymatic immune modulators present in two isoforms - ADA-1 and ADA-2. Infants exhibit low ADA activity, resulting in high plasma adenosine concentrations and a consequent anti-inflammatory/anti-Th1 bias. While longitudinal studies of plasma ADA have been conducted in infants in The Gambia (GAM), little is known regarding ADA trajectories in other parts of the world.

Methods

Herein, we characterized plasma ADA activity in an infant cohort in Papua New Guinea (PNG; n=83) and compared to ontogeny of ADA activity in a larger cohort in GAM (n=646). Heparinized peripheral blood samples were collected at day of life (DOL) 0, DOL7, DOL30, and DOL128. Plasma ADA-1, ADA-2, and total ADA activities were measured by chromogenic assay.

Results

Compared to GAM infants, PNG infants had significantly lower ADA-1 (0.9-fold), ADA-2 (0.42-fold), and total ADA (0.84-fold) activities at birth which converged by DOL30.

Discussion

Overall, discovery of a distinct baseline and a consistent pattern of increasing plasma ADA activity in early life in two genetically and geographically distinct populations validates and extends previous findings on the robustness of early life immune ontogeny.

Deficiency of Adenosine Deaminase 2

Adenosine deaminase 2 (ADA2) deficiency is an autosomal recessively inherited autoinflammatory disorder caused by loss-of-function mutations in the ADA2 gene. Although the pathogenesis involves the triggering of a proinflammatory cascade due to increased production of inflammatory cytokines such as tumor necrosis factor (TNF)-α and dysregulation of neutrophil extracellular trap formation resulting from an excess accumulation of extracellular adenosine, the pathogenetic mechanism still needs further clarification due to the broad clinical spectrum. In addition to the initially described vasculitis-related symptoms, hematological, immunological, and autoinflammatory symptoms are now well recognized. The diagnosis is made by demonstration of pathogenic variants of ADA2 with biallelic loss of function and identification of low plasma ADA2 catalytic activity. Currently, TNF-α inhibitors are the treatment of choice for controlling vasculitis manifestations and preventing strokes. However, in patients presenting with severe hematologic findings, TNF-α inhibitors are not the treatment of choice and hematopoietic stem cell transplantation has been shown to be successful in selected cases. Recombinant ADA2 protein and gene therapy are promising treatment modalities for the future. In conclusion, ADA2 deficiency has a broad phenotype and should be considered in the differential diagnosis of different clinical situations. In this review, we summarize the disease manifestations of ADA2 deficiency and available treatment options.

A case report on deficiency of adenosine deaminase 2 with relapse-remission course and analysis of genotype-phenotype correlation

Deficiency of adenosine deaminase 2 (DADA2) is a monogenic disease caused by biallelic mutations in adenosine deaminase 2 (ADA2). The varying phenotypes of the disease often lead to delayed diagnosis or misdiagnosis. We report an 11-year-old boy with DADA2 and provide a preliminary analysis of genotype-phenotype correlation. The age of onset of the disease was 8 years old. The disease successively involved the brainstem, muscles, joints, and cerebrum. After three relapse-remission episodes over 3 years, the patient was finally diagnosed with DADA2 by whole-exome sequencing. Compound heterozygous variants in the ADA2 gene (NM_001282225.2: c.1072G>A, p.Gly358Arg; c.419dupC, p.Arg141Lysfs*37) were found in the patient. He did not receive anti-TNF therapy and had no relapse after a 8-month follow-up. We identified a novel variant of the ADA2 gene, and the associated disease course may follow a relapse-remission pattern. Homozygous mutations of p.Gly358Arg can cause pure red cell aplasia, whereas compound heterozygous variations may lead to different phenotypes. Variants in the catalytic domain and frameshift mutations may also cause relatively benign phenotypes besides causing hematological disorders. Further studies are needed to clarify the genotypic-phenotypic relationship of this disease.

LC-MS-based rheumatoid arthritis serum metabolomics reveals the role of deoxyinosine in attenuating collagen-induced arthritis in mice

Rheumatoid arthritis (RA) is a persistent autoimmune condition with no identified cure currently. Recently, scientists have applied metabolomics to investigate altered metabolic profiles and unique diseases-associated metabolic signatures. Herein, we applied metabolomics approach to analyze serum samples of 41 RA patients and 42 healthy controls (HC) with the aim to characterize RA patients' metabolic profile, investigate related underlying pathological processes, and identify target metabolites. By utilizing ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry, we found 168 proposed metabolites and 45 vital metabolic pathways. Our analysis revealed that deoxyinosine (DI), a metabolite of the purine metabolic pathway, was the most significant reduced metabolite in RA patients. Furthermore, through targeted detection, we confirmed lower concentration of DI in RA patients' peripheral blood. Moreover, DI inhibited lipopolysaccharide-induced inflammation both in vitro and in vivo. We further assessed DI's therapeutic potential in a collagen-induced arthritis (CIA) murine model. The results revealed that DI attenuated CIA, as evidenced by significantly lowered clinical scores of arthritis, alleviated joint swelling, and mitigated bone destruction. Moreover, we elucidated the underlying mechanism by which DI increased the population of myeloid-derived suppressor cells (MDSCs) and suppressed the proliferation of induced T cells. Collectively, these findings suggested that DI potentially ameliorated RA by inducing immunosuppressive MDSCs. The study provides key observations on RA pathogenesis and may contribute to developing novel therapeutic strategies for this debilitating condition.

A Novel Ultrafiltrate Extract of Propolis Exerts Anti-inflammatory Activity through Metabolic Rewiring

Thousands of years ago, humans started to use propolis because of its medicinal properties, and modern science has successfully identified several bioactive molecules within this resinous bee product. However, a natural propolis extract which has been removed the adhesive glue and preserved propolis bioactive compounds is urgently needed to maximise the therapeutic opportunities. In this study, a novel ultrafiltrate fraction from Brazilian green propolis, termed P30K, was demonstrated with anti-inflammatory properties, both in vitro and in vivo. Total flavonoids and total phenolic acids content in P30K were 244.6 mg/g and 275.8 mg/g respectively, while the IC50 value of inhibition of cyclooxygenase-2 (COX-2) was 8.30 μg/mL. The anti-inflammatory activity of P30K was furtherly corroborated in experimental models of lipopolysaccharides (LPS)-induced acute liver and lung injury. Mechanistically, integrated GC-MS and LC-MS based serum metabolomics analysis revealed that P30K modulated citrate cycle (TCA), pyruvate, glyoxylate and dicarboxylate metabolism pathways to inhibit secretion of pro-inflammatory cytokines. Results of network pharmacology and molecular docking suggested that P30K targeted catechol-O-methyltransferases (COMT), 11β-hydroxysteroid dehydrogenases (HSD11B1), and monoamine oxidases (MAOA and MAOB) to promote cellular metabolomic rewiring. Collectively, our work reveals P30K as an efficient therapeutic agent against inflammatory conditions and its efficacy is related to metabolic rewiring.

Impaired Mitochondrial Function and Marrow Failure in Patients Carrying a Variant of the SRSF4 Gene

Serine/arginine-rich splicing factors (SRSFs) are a family of proteins involved in RNA metabolism, including pre-mRNA constitutive and alternative splicing. The role of SRSF proteins in regulating mitochondrial activity has already been shown for SRSF6, but SRSF4 altered expression has never been reported as a cause of bone marrow failure. An 8-year-old patient admitted to the hematology unit because of leukopenia, lymphopenia, and neutropenia showed a missense variant of unknown significance of the SRSF4 gene (p.R235W) found via whole genome sequencing analysis and inherited from the mother who suffered from mild leuko-neutropenia. Both patients showed lower SRSF4 protein expression and altered mitochondrial function and energetic metabolism in primary lymphocytes and Epstein-Barr-virus (EBV)-immortalized lymphoblasts compared to healthy donor (HD) cells, which appeared associated with low mTOR phosphorylation and an imbalance in the proteins regulating mitochondrial biogenesis (i.e., CLUH) and dynamics (i.e., DRP1 and OPA1). Transfection with the wtSRSF4 gene restored mitochondrial function. In conclusion, this study shows that the described variant of the SRSF4 gene is pathogenetic and causes reduced SRSF4 protein expression, which leads to mitochondrial dysfunction. Since mitochondrial function is crucial for hematopoietic stem cell maintenance and some genetic bone marrow failure syndromes display mitochondrial defects, the SRSF4 mutation could have substantially contributed to the clinical phenotype of our patient.

Deficiency of Adenosine Deaminase 2: Clinical Manifestations, Diagnosis, and Treatment

Deficiency of adenosine deaminase 2 (DADA2) is a monogenic vasculitis syndrome caused by biallelic mutations in the adenosine deaminase 2 gene. The diagnosis of DADA2 is confirmed by decreased enzymatic activity of ADA2 and genetic testing. Symptoms range from cutaneous vasculitis and polyarteritis nodosa-like lesions to stroke. The vasculopathy of DADA2 can affect many organ systems, including the gastrointestinal and renal systems. Hematologic manifestations occur early with hypogammaglobulinemia, lymphopenia, pure red cell aplasia, or pancytopenia. Treatment can be challenging. Tumor necrosis factor inhibitors are helpful to control inflammatory symptoms. Hematopoietic stem cell transplant may be needed to treat refractory cytopenias, vasculopathy, or immunodeficiency.

Similarities in the induction of the intracellular pathogen response in Caenorhabditis elegans and the type I interferon response in mammals

Although the type-I interferon (IFN-I) response is considered vertebrate-specific, recent findings about the Intracellular Pathogen Response (IPR) in nematode Caenorhabditis elegans indicate that there are similarities between these two transcriptional immunological programs. The IPR is induced during infection with natural intracellular fungal and viral pathogens of the intestine and promotes resistance against these pathogens. Similarly, the IFN-I response is induced by viruses and other intracellular pathogens and promotes resistance against infection. Whether the IPR and the IFN-I response evolved in a divergent or convergent manner is an unanswered and exciting question, which could be addressed by further studies of immunity against intracellular pathogens in C. elegans and other simple host organisms. Here we highlight similar roles played by RIG-I-like receptors, purine metabolism enzymes, proteotoxic stressors, and transcription factors to induce the IPR and IFN-I response, as well as the similar consequences of these defense programs on organismal development.

A Narrative Review of the Neurological Manifestations of Human Adenosine Deaminase 2 Deficiency

Deficiency of human adenosine deaminase type 2 (DADA2) is a complex systemic autoinflammatory disorder characterized by vasculopathy, immune dysregulation, and hematologic abnormalities. The most notable neurological manifestations of DADA2 are strokes that can manifest with various neurological symptoms and are potentially fatal. However, neurological presentations can be diverse. We here present a review of the neurological manifestations of DADA2 to increase clinical awareness of DADA2 as the underlying diagnosis. We reviewed all published cases of DADA2 from 1 January 2014 until 19 July 2022 found via PubMed. A total of 129 articles describing the clinical features of DADA2 were included in the analysis. Six hundred twenty-eight patients diagnosed with DADA2 were included in the review. 50.3% of patients had at least signs of one reported neurological event, which was the initial or sole manifestation in 5.7% and 0.6%, respectively. 77.5% of patients with neurological manifestations had at least signs of one cerebrovascular accident, with lacunar strokes being the most common and 35.9% of them having multiple stroke episodes. There is a remarkable predilection for the brain stem and deep gray matter, with 37.3% and 41.6% of ischemic strokes, respectively. Other neurological involvement included neuropathies, focal neurological deficits, ophthalmological findings, convulsions, and headaches. In summary, neurological manifestations affect a significant proportion of patients with DADA2, and the phenotype is broad. Neurological manifestations can be the first and single manifestation of DADA2. Therefore, stroke, encephalitis, posterior reversible encephalopathy syndrome, mononeuropathy and polyneuropathy, and Behçet's disease-like presentations should prompt the neurologist to exclude DADA2, especially but not only in childhood.

Vasculitis associated with adenosine deaminase 2 deficiency: at the crossroads between Behçet's disease and autoinflammation. A viewpoint

Adenosine deaminase 2 deficiency (DADA2) is a rare monogenic vasculopathy caused by loss-of-function homozygous or compound heterozygous mutations in ADA2, formerly CECR1 (cat eye syndrome chromosome region 1) gene. The DADA2 phenotype is widely heterogeneous, and patients may present with fever, weight loss, livedo reticularis/racemosa, digital ischemia, cutaneous ulceration, peripheral neuropathy, abdominal pain, bowel perforation, and portal or nephrogenic hypertension. More specific manifestations include early-onset ischemic or hemorrhagic stroke, mild immunodeficiency and hypogammaglobinemia, cytopenia, and vision disturbances. Herein, we present the case of a young male with vasculitis associated with DADA2. The presence of HLA-B51 and the clinical features of this patient raised the question of similarities between ADA2 deficiency, Behçet's disease, and NOD2-associated diseases. Treatment of this rare monogenic disease is challenging and based on small case series. The long-term experience of this patient proved the difficulties of prednisone tapering and the lack of satisfactory therapeutic strategies.

Co-inhibition of adenosine 2b receptor and programmed death-ligand 1 promotes the recruitment and cytotoxicity of natural killer cells in oral squamous cell carcinoma

Adenosine promotes anti-tumor immune responses by modulating the functions of T-cells and natural killer (NK) cells in the tumor microenvironment; however, the role of adenosine receptors in the progression of oral squamous cell carcinoma (OSCC) and its effects on immune checkpoint therapy remain unclear. In this study, we obtained the tumor tissues from 80 OSCC patients admitted at the Shandong University Qilu Hospital between February 2014 and December 2016. Thereafter, we detected the expression of adenosine 2b receptor (A2BR) and programmed death-ligand 1 (PD-L1) using immunohistochemical staining and analyzed the association between their expression in different regions of the tumor tissues, such as tumor nest, border, and paracancer stroma. To determine the role of A2BR in PD-L1 expression, CAL-27 (an OSCC cell line) was treated with BAY60-6583 (an A2BR agonist), and PD-L1 expression was determined using western blot and flow cytometry. Furthermore, CAL-27 was treated with a nuclear transcription factor-kappa B (NF-κ B) inhibitor, PDTC, to determine whether A2BR regulates PD-L1 expression via the NF-κ B signaling pathway. Additionally, a transwell assay was performed to verify the effect of A2BR and PD-L1 on NK cell recruitment. The results of our study demonstrated that A2BR and PD-L1 are co-expressed in OSCC. Moreover, treatment with BAY60-6583 induced PD-L1 expression in the CAL-27 cells, which was partially reduced in cells pretreated with PDTC, suggesting that A2BR agonists induce PD-L1 expression via the induction of the NF-κ B signaling pathway. Furthermore, high A2BR expression in OSCC was associated with lower infiltration of NK cells. Additionally, our results demonstrated that treatment with MRS-1706 (an A2BR inverse agonist) and/or CD274 (a PD-L1-neutralizing antibody) promoted NK cell recruitment and cytotoxicity against OSCC cells. Altogether, our findings highlight the synergistic effect of co-inhibition of A2BR and PD-L1 in the treatment of OSCC via the modulation of NK cell recruitment and cytotoxicity.

Inborn Errors of Purine Salvage and Catabolism

Cellular purine nucleotides derive mainly from de novo synthesis or nucleic acid turnover and, only marginally, from dietary intake. They are subjected to catabolism, eventually forming uric acid in humans, while bases and nucleosides may be converted back to nucleotides through the salvage pathways. Inborn errors of the purine salvage pathway and catabolism have been described by several researchers and are usually referred to as rare diseases. Since purine compounds play a fundamental role, it is not surprising that their dysmetabolism is accompanied by devastating symptoms. Nevertheless, some of these manifestations are unexpected and, so far, have no explanation or therapy. Herein, we describe several known inborn errors of purine metabolism, highlighting their unexplained pathological aspects. Our intent is to offer new points of view on this topic and suggest diagnostic tools that may possibly indicate to clinicians that the inborn errors of purine metabolism may not be very rare diseases after all.

Case Report: Patient with deficiency of ADA2 presenting leukocytoclastic vasculitis and pericarditis during infliximab treatment

Deficiency of adenosine deaminase 2 (DADA2), first reported in 2014, is a disease with great phenotypic variability, which has been increasingly reported. Therapeutic response depends on the phenotype. We present a case of an adolescent with recurrent fever, oral aphthous ulcers, and lymphadenopathy from 8 to 12 years of age and subsequently presented with symptomatic neutropenia. After the diagnosis of DADA2, therapy with infliximab was started, but after the second dose, she developed leukocytoclastic vasculitis and showed symptoms of myopericarditis. Infliximab was switched to etanercept, with no relapses. Despite the safety of tumor necrosis factor alpha inhibitors (TNFi), paradoxical adverse effects have been increasingly reported. The differential diagnosis between disease new-onset manifestations of DADA2 and side effects of TNFi can be challenging and warrants further clarification.

A case series of ten plus one deficiency of adenosine deaminase 2 (DADA2) patients in Iran

BACKGROUND

Deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessive autoinflammatory disease caused by mutations in the ADA2 gene. DADA2 has a broad spectrum of clinical presentations. Apart from systemic manifestations, we can categorize most of the signs and symptoms of DADA2 into the three groups of vasculitis, hematologic abnormalities, and immunologic dysregulations. The most dominant vasculitis features are skin manifestations, mostly in the form of livedo racemosa/reticularis, and early onset ischemic or hemorrhagic strokes. Hypogammaglobulinemia that is found in many cases of DADA2 brings immunodeficiencies into the differential diagnosis. Cytopenia, pure red cell aplasia (PRCA), and bone marrow failure (BMF) are the hematologic abnormalities commonly found in DADA.

CASE PRESENTATION

We introduce eleven patients with DADA2 diagnosis, including two brothers and sisters, one set of twin sisters, and one father and his daughter and son. Ten patients (91%) had consanguineous parents. All the patients manifested livedo racemose/reticularis. Ten patients (91%) reported febrile episodes, and seven (64%) had experienced strokes. Only one patient had hypertension. Two of the patients (11%) presented decreased immunoglobulin levels. One of the patients presented with PRCA. Except for the PRCA patient with G321E mutation, all of our patients delivered G47R mutation, the most common mutation in DADA2 patients. Except for one patient who unfortunately passed away before the diagnosis was made and proper treatment was initiated, the other patients' symptoms are currently controlled; two of the patients presented with mild symptoms and are now being treated with colchicine, and the eight others responded well to anti-TNFs. The PRCA patient still suffers from hematologic abnormalities and is a candidate for a bone marrow transplant.

CONCLUSIONS

Considering the manifestations and the differential diagnoses, DADA2 is not merely a rheumatologic disease, and introducing this disease to hematologists, neurologists, and immunologists is mandatory to initiate prompt and proper treatment. The efficacy of anti-TNFs in resolving the symptoms of DADA2 patients have been proven, but not for those with hematologic manifestations. Similarly, they were effective in controlling the symptoms of our cohort of patients, except for the one patient with cytopenia.

Immune dysregulation

The understanding of immune dysregulation in many different diseases continues to grow. There is increasing evidence that altered microbiome and gut barrier dysfunction contribute to systemic inflammation in patients with primary immunodeficiency and in patients with rheumatic disease. Recent research provides insight into the process of induction and maturation of pathogenic age-associated B cells and highlights the role of age-associated B cells in creating tissue inflammation. T follicular regulatory cells are shown to help maintain B-cell tolerance, and therapeutic approaches to increase or promote T follicular regulatory cells may help prevent or decrease immune dysregulation. Meanwhile, novel studies of systemic-onset juvenile idiopathic arthritis reveal a strong HLA association with interstitial lung disease and identify key aspects of the pathogenesis of macrophage activation syndrome. Studies of hyperinflammatory syndromes, including the recently described multisystem inflammatory syndrome of children, characterize similarities and differences in cytokine profiles and T-cell activation. This review focuses on recent advances in the understanding of immune dysregulation and describes potential key factors that may function as biomarkers for disease or targets for therapeutic interventions. Future trials are necessary to address the many remaining questions with regards to pathogenesis, diagnosis, and treatment of autoimmune, inflammatory, and immunodeficiency syndromes.