Anti-GABAB receptor encephalitis: clinical and laboratory characteristics, imaging, treatments and prognosis.

Introduction: Anti-GABABR encephalitis is a rare disease reported to be often associated with tumors. The current study aims to summarize the clinical characteristics, imaging features, treatments, outcomes and explore the potential prognosis risk factors of patients with anti-GABABR encephalitis. Methods: Patients tested positive for anti-GABABR were retrospective studied from a single medical center in China over a period of 3 years. They were followed up for a maximum period of 18 months. Clinical data were summarized and prognostic factors including demographic characteristics, laboratory tests, and neurological functions were compared between survived and deceased patients at 18 months follow-up. Results: Twenty-six patients, 10 females (38.5%) and 16 males (61.5%), diagnosed with anti-GABABR encephalitis were studied. The median age was 58 years. Of the 23 cases with complete clinical data, their main manifestations were epileptic seizures (65%), mental and behavioral abnormalities (52%), and cognitive impairment (48%). 7 (30.4%) cases had tumors: 5 small cell lung cancer (SCLC), 1 rectum adenocarcinoma (moderately differentiated) and 1 esophageal squamous cell carcinoma. MRI showed 5 (22%) cases had T2 FLAIR increased signals in cortex but with different regions affected. One of the two patients scanned for PET-CT showed hypermetabolism in the left temporal lobe region. The disease course ranged from 5 days to 3 years. 2 patients (one had esophageal carcinoma) without immunotherapy and 3 patients (one had SCLC) that did not response to immunotherapy died soon after diagnosis. 18 patients improved after immunotherapy while 3 (all had SCLC) died after relapses. The prevalence of epileptic seizures and malignancies was significantly lower in the survival group than in the deceased group at 18-months follow-up, the same as the admission mRs score. Serum fibrinogen, cerebrospinal fluid immunoglobulin G quotient, and 24-hour intrathecal synthesis rate were significantly lower in the survival groups as well. Conclusions: Cortex T2 FLAIR abnormalities were only observed in a small proportion of anti-GABABR encephalitis patients with heterogeneous MRI phenotypes. High mRS score at admission, epileptic seizures and the presence of a tumor indicated a poor prognosis, while the underlying mechanism of the later two factors should be investigated further.

Therapeutic Drug Monitoring of Infliximab and Adalimumab through Concentration and Anti-Drug Antibodies Assessment; Comparison of Sanquin Diagnostics and Theradiag Assays.

BACKGROUND: Therapeutic drug monitoring of biological Tumor Necrosis Factor (TNF)-alpha inhibitors is of critical importance. In this study, the performance of practically advantageous chemiluminescent immunoassays of Theradiag, assessing Infliximab and Adalimumab serum concentrations and anti-drug antibodies (ADA) against these biologics, were compared to the Enzyme-Linked Immuno-Sorbent Assays (ELISAs) from Sanquin Diagnostics. METHODS: Leftover serum samples (n = 80 for each parameter) from patients treated with Infliximab or Adalimumab were collected. Correlation and agreement analyses for serum concentration and ADAs, respectively, were performed. Both Theradiag ADA assays, an assay targeting both free and bound ADAs and an assay targeting solely free ADAs, were investigated and compared to the Sanquin Diagnostics ADA assay, targeting both free and bound ADAs. RESULTS: Strong positive correlations were observed between the biologic concentration assessment of Infliximab (Spearman's Rho = 0.91) and Adalimumab (Spearman's Rho = 0.94). However, there appeared to be significant bias in the Theradiag assay when compared to Sanquin (Infliximab median (Confidence Interval (CI)) = 2.1 (1.7-2.6) µg/mL; Adalimumab median (CI) = 0.8 (0.5-0.9) µg/mL). Agreement analyses showed moderate to good agreement for the Theradiag and Sanquin Diagnostics ADA assays, when detecting both free and bound ADAs, for Infliximab (Cohen's k = 0.717) and Adalimumab (Cohen's k = 0.802). In contrast, the Theradiag ADA assay detecting solely free ADAs had zero to poor agreement for Infliximab (Cohen's k = 0.458) and Adalimumab (Cohen's k = 0.119), respectively. CONCLUSIONS: This study demonstrated strong correlations and good agreement between the Theradiag and Sanquin Diagnostics assays measuring Infliximab and Adalimumab serum concentrations and ADAs, both free and bound, against these biologics. Discordance analyses showed significantly decreased drug concentrations in the solely free assays, indicating that the combined detection of free and bound ADAs better aligns with drug levels.

The intrinsic coagulation pathway plays a dominant role in driving hypercoagulability in ANCA-associated vasculitis.

ABSTRACT: The risk of a venous thrombotic event (VTE) is increased in patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV); however, a detailed understanding of the underlying mechanisms of hypercoagulability is limited. We assessed prospectively different coagulation parameters in 71 patients with active AAV at baseline and after 6 months of follow-up. D-dimers and fibrinogen were increased in most patients at presentation and remained elevated in half of the patients. Particularly, thrombin-antithrombin (T:AT) complex and activated coagulation factors in complex with their natural inhibitors of the intrinsic coagulation pathway (ie, activated FXII:C1 esterase inhibitor [FXIIa:C1Inh], FXIa:AT, and FXIa:alpha1-antitrypsin [FXIa:α1AT]) were profoundly elevated in patients at baseline. Thrombin formation was dominantly correlated with coagulation factors of the intrinsic pathway (ie, FXIIa:AT, FXIa:AT, FXIa:α1AT, and FXIa:C1Inh) compared to the extrinsic pathway (ie, FVIIa:AT). Hypercoagulability correlated with higher disease activity, ANCA levels, C-reactive protein, serum creatinine, and proteinuria. VTEs were observed in 5 out of 71 (7%) patients within 1 month (interquartile range, 1-5) after inclusion. Baseline T:AT levels were significantly higher in patients with VTE than in those without VTE (P = .044), but other clinical or laboratory markers were comparable between both groups. Hypercoagulability is dominantly characterized by activation of the intrinsic coagulation pathway and elevated D-dimers in active AAV. The driving factors of hypercoagulability are yet to be studied but are most likely related to an interplay of increased disease activity, vascular inflammation, and endothelial damage. Future targets for intervention could include inhibitors of the intrinsic coagulation pathway and compounds specifically reducing the hyperinflammatory state.

Plasma Dephosphorylated-Uncarboxylated Matrix Gla-Protein in Systemic Sclerosis Patients: Biomarker Potential for Vascular Calcification and Inflammation.

BACKGROUND: Systemic sclerosis (SSc) patients face an elevated risk of cardiovascular disease (CVD), even when classic cardiovascular risk factors are considered. Plasma dephosphorylated-uncarboxylated Matrix Gla-protein (dp-ucMGP), an inactive form of MGP, is associated with increased CVD risk. Smooth muscle cells, implicated in SSc's development, are the primary dp-ucMGP producers. This study assessed dp-ucMGP levels and initial CVD events in early-diagnosed SSc patients, investigating its potential as a CVD and all-cause mortality predictor over time. METHODS: In a cohort of 87 SSc patients (excluding those with pre-existing CVD or on dialysis), baseline dp-ucMGP levels were measured, along with cardiovascular risk factors. Validation involved assessing dp-ucMGP in a subset of treatment-naive SSc patients. RESULTS: A significantly elevated median dp-ucMGP level of 634 pmol/L (IQR 301) compared with healthy controls (dp-ucMGP < 393 pmol/L; p < 0.001) was observed. Validation in a treatment-naive SSc patient subset yielded similar results (median 589 pmol/L; IQR 370). During a median 10.5-year follow-up among 78 SSc patients, 33.3% experienced their first CVD event, independent of traditional risk factors. Elevated dp-ucMGP levels (>634 pmol/L) correlated with a higher risk of CVD and/or death (log-rank test: p < 0.01). CONCLUSIONS: In summary, dp-ucMGP emerges as a novel biomarker in SSc patients, with elevated levels indicating an increased risk of CVD and/or mortality in this population.

Identifying therapeutic monoclonal antibodies using target protein collision electrophoresis reflex assay to separate the wheat from the chaff.

Monoclonal gammopathies are characterized by the presence of monoclonal immunoglobulins, also known as M-proteins. Therapeutic monoclonal antibodies (t-mAbs) can interfere in laboratory assays used to monitor the state of disease, such as serum protein electrophoresis (SPE) and immunofixation electrophoresis (IFE). To establish a correct interpretation of IFE, Target protein-Collision Immunofixation Electrophoresis Reflex Assay (T-CIERA) was developed to identify t-mAbs in IFE. Here we demonstrate that T-CIERA is applicable to a wide variety of t-mAbs for which the target protein is commercially available. Moreover, the shift observed was characteristic for each t-mAb, and T-CIERA enabled the identification of multiple t-mAbs sharing a common target protein. Additionally, the lower limit of detection (LLOD) was determined objectively, and T-CIERA demonstrated an adequate LLOD for all tested t-mAbs. Furthermore, T-CIERA was also successfully applied to serum samples obtained from patients receiving daratumumab, isatuximab, elotuzumab, and durvalumab treatment. In conclusion, T-CIERA is a suitable reflex assay for identifying a wide variety of t-mAbs, including those for which no commercial assay is available to deal with their interference. Moreover, CD38-CIERA could serve as an alternative or complementary test to the commercially available Hydrashift assay kits. T-CIERA would enable laboratories without mass spectrometry equipment and expertise in this area to distinguish between drug and disease to improve clinical response monitoring and diagnosis of monoclonal gammopathies.

Anti-GAD65 autoantibody levels measured by ELISA and alternative types of immunoassays in relation to neuropsychiatric diseases versus diabetes mellitus type 1.

Background: Anti-GAD65 autoantibodies (GAD65-Abs) may occur in patients with epilepsy and other neurological disorders, but the clinical significance is not clear-cut. Whereas high levels of GAD65-Abs are considered pathogenic in neuropsychiatric disorders, low or moderate levels are only considered as mere bystanders in, e.g., diabetes mellitus type 1 (DM1). The value of cell-based assays (CBA) and immunohistochemistry (IHC) for GAD65-Abs detection has not been clearly evaluated in this context. Objective: To re-evaluate the assumption that high levels of GAD65-Abs are related to neuropsychiatric disorders and lower levels only to DM1 and to compare ELISA results with CBA and IHC to determine the additional value of these tests. Methods: 111 sera previously assessed for GAD65-Abs by ELISA in routine clinical practice were studied. Clinical indications for testing were, e.g., suspected autoimmune encephalitis or epilepsy (neuropsychiatric cohort; n = 71, 7 cases were initially tested positive for GAD65-Abs by ELISA), and DM1 or latent autoimmune diabetes in adults (DM1/LADA cohort (n = 40, all were initially tested positive)). Sera were re-tested for GAD65-Abs by ELISA, CBA, and IHC. Also, we examined the possible presence of GAD67-Abs by CBA and of other neuronal autoantibodies by IHC. Samples that showed IHC patterns different from GAD65 were further tested by selected CBAs. Results: ELISA retested GAD65-Abs level in patients with neuropsychiatric diseases was higher than in patients with DM1/LADA (only retested positive samples were compared; 6 vs. 38; median 47,092 U/mL vs. 581 U/mL; p = 0.02). GAD-Abs showed positive both by CBA and IHC only if antibody levels were above 10,000 U/mL, without a difference in prevalence between the studied cohorts. We found other neuronal antibodies in one patient with epilepsy (mGluR1-Abs, GAD-Abs negative), and in a patient with encephalitis, and two patients with LADA. Conclusion: GAD65-Abs levels are significantly higher in patients with neuropsychiatric disease than in patients with DM1/LADA, however, positivity in CBA and IHC only correlates with high levels of GAD65-Abs, and not with the underlying diseases.

Predictive Value of Serum Neurofilament Light Chain Levels in Anti-NMDA Receptor Encephalitis.

BACKGROUND AND OBJECTIVES: Determinants of disease activity and prognosis are limited in anti-NMDA receptor (NMDAR) encephalitis. Neurofilament light chains (NfL) are markers of axonal damage and have been identified as valuable biomarkers for neurodegenerative and other neuroinflammatory disorders. We aimed to investigate serum NfL levels in patients with anti-NMDAR encephalitis as a biomarker for disease severity and outcome. METHODS: In this retrospective study, NfL values were measured in all available pretreatment serum and paired CSF samples of the nationwide anti-NMDAR encephalitis cohort. The values were analyzed in duplicate using single-molecule array and compared with measurements in healthy references. Follow-up sera were tested to analyze longitudinal responsiveness, if at least available from 2 time points after diagnosis. Serum NfL levels were compared with data on disease activity (seizures, MRI, and CSF findings), severity (modified Rankin Scale [mRS] score, admission days, and intensive care unit admission), and outcome (mRS score and relapses), using regression analysis. RESULTS: We have included 71 patients (75% female; mean age 31.4 years, range 0-85 years) of whom pretreatment serum samples were analyzed. Paired CSF samples were available of 33 patients, follow-up serum samples of 20 patients. Serum NfL levels at diagnosis were higher in patients (mean 19.5 pg/mL, 95% CI 13.7-27.7) than in references (mean 6.4 pg/mL, 95% CI 5.8-7.2, p < 0.0001). We observed a good correlation between serum and CSF NfL values (R = 0.84, p < 0.0001). Serum NfL levels and age correlated in patients (Pearson R = 0.57, p < 0.0001) and references (R = 0.62, p < 0.0001). Increased NfL values were detected in patients post-herpes simplex virus 1 encephalitis (mean 248.8 vs 14.1 pg/mL, p < 0.0001) and in patients with brain MRI lesions (mean 27.3 vs 11.1 pg/mL, p = 0.019). NfL levels did relate to the long-term follow-up (mRS score at 12 months; ßNfL = 0.55, p = 0.013), although largely explained by the effect of age on NfL levels and prognosis. In serial samples, NfL values did roughly follow clinical disease activity, albeit with delay. DISCUSSION: Increased serum NfL levels reflect neuroaxonal damage in anti-NMDAR encephalitis. No relationship was identified with disease severity, whereas the association with outcome was confounded by age. The implied role of sampling timing on NfL levels also limits the applicability of NfL as a prognostic marker.

Assessment of longitudinal serum neutrophil extracellular trap-inducing activity in anti-neutrophil cytoplasmic antibody-associated vasculitis and glomerulonephritis in a prospective cohort using a novel bio-impedance technique.

Neutrophil extracellular traps (NET) have been implicated in the pathogenesis of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). Here, we developed a novel, label-free, high-throughput bio-impedance technique to effectively measure serum NET-inducing activity. Using this technique, NET-inducing activity of serum derived from patients with AAV was assessed in a prospective cohort of 62 patients presenting with active AAV with major organ involvement. Thirty-five patients presented with new and 27 patients presented with relapsing AAV, of whom 38 had kidney and/or 31 had lung involvement. NET-inducing activity was assessed at diagnosis of active AAV (time zero), during the first 6 weeks of treatment, and after 6 months of treatment. Forty-seven patients revealed elevated NET-inducing activity at time zero. After initiation of immunosuppressive treatment, NET-inducing activity was reduced at six weeks. A subsequent increase at six months could potentially identify patients with relapsing disease (hazard ratio, 11.45 [interquartile range 1.36-96.74]). NET-inducing activity at time zero correlated with kidney function and proteinuria. Importantly, in kidney tissue, NETs co-localized with lesions typical of ANCA-associated glomerulonephritis and even correlated with systemic serum NET-inducing activity. Thus, our prospective data corroborate the importance of NET formation in AAV and ANCA-associated glomerulonephritis and the potential of longitudinal evaluation, as monitored by our novel bio-impedance assay and detailed histological evaluation.

Hypoxia-Driven Changes in a Human Intestinal Organoid Model and the Protective Effects of Hydrolyzed Whey.

Many whey proteins, peptides and protein-derived amino acids have been suggested to improve gut health through their anti-oxidant, anti-microbial, barrier-protective and immune-modulating effects. Interestingly, although the degree of hydrolysis influences peptide composition and, thereby, biological function, this important aspect is often overlooked. In the current study, we aimed to investigate the effects of whey protein fractions with different degrees of enzymatic hydrolysis on the intestinal epithelium in health and disease with a novel 2D human intestinal organoid (HIO) monolayer model. In addition, we aimed to assess the anti-microbial activity and immune effects of the whey protein fractions. Human intestinal organoids were cultured from adult small intestines, and a model enabling apical administration of nutritional components during hypoxia-induced intestinal inflammation and normoxia (control) in crypt-like and villus-like HIO was established. Subsequently, the potential beneficial effects of whey protein isolate (WPI) and two whey protein hydrolysates with a 27.7% degree of hydrolysis (DH28) and a 50.9% degree of hydrolysis (DH51) were assessed. In addition, possible immune modulatory effects on human peripheral immune cells and anti-microbial activity on four microbial strains of the whey protein fractions were investigated. Exposure to DH28 prevented paracellular barrier loss of crypt-like HIO following hypoxia-induced intestinal inflammation with a concomitant decrease in hypoxia inducible factor 1 alpha (HIF1α) mRNA expression. WPI increased Treg numbers and Treg expression of cluster of differentiation 25 (CD25) and CD69 and reduced CD4+ T cell proliferation, whereas no anti-microbial effects were observed. The observed biological effects were differentially mediated by diverse whey protein fractions, indicating that (degree of) hydrolysis influences their biological effects. Moreover, these new insights may provide opportunities to improve immune tolerance and promote intestinal health.

Adding low dose cyclophosphamide to rituximab for remission-induction may prolong relapse-free survival in patients with ANCA vasculitis: A retrospective study.

Objective: Rituximab (RTX) and cyclophosphamide (CYC) are effective remission-induction therapies in anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). However, combining these therapies may favor prognosis in patients with a major disease presentation. We conducted a retrospective study to compare patients treated with a combination of RTX and low dose CYC (RTX-CYC) or with RTX only, both followed by tailored maintenance with RTX, with regard to long-term outcomes. Methods: Patients treated in the Maastricht University Medical Center between March 2007 and January 2019, were screened for eligibility. The primary outcome variable was major relapse rate after two and five years. Secondary outcome variables were clinical data and laboratory parameters. Results: Of the 246 screened patients, 34 received RTX-CYC and 28 RTX only for remission-induction. All patients were followed for at least two years, with a median follow-up of 48 months (IQR 24-60). At baseline, renal involvement was more prevalent in the RTX-CYC patients (85% vs. 61%, P = 0.028). Major relapse rates within two years, but not after five years, were significantly lower in the RTX-CYC group (3% vs. 24%, P = 0.032). The rate of infections, hypogammaglobulinemia, end-stage renal disease, malignancies, and mortality did not differ after two and five years. Conclusion: Adding low dose CYC to RTX is safe and may prevent major relapses in patients with severe AAV in the first two years after remission-induction. Randomized controlled trials that compare the efficacy and safety between RTX and a combination of RTX with CYC are needed.

Annexin A1 Is Associated with Adverse Clinical Outcomes in Patients with COVID-19.

Severe coronavirus disease 2019 (COVID-19) is characterized by hyperinflammation, vascular damage, and hypercoagulability. Insufficient responses of Annexin A1 (AnxA1), a pro-resolving inhibitor of neutrophil infiltration and activation, might contribute to a severe course of the disease. We longitudinally evaluated AnxA1's role in terms of inflammation, vascular damage, and clinical outcomes in a large prospective cohort of patients with COVID-19. AnxA1 was measured at presentation and during follow-up in the sera of 220 consecutive patients who presented at our hospital during the first wave. AnxA1 was significantly higher in the moderate and severe cases of COVID-19 compared to the healthy controls. Elevated AnxA1 was associated with markers of inflammation and endothelial damage. AnxA1 was significantly higher in patients with thrombotic events and ICU admission. Multivariable logistic regression indicated baseline AnxA1 (per ten units) as a predictor of thrombotic events. Linear mixed models predicted that AnxA1 tended to increase more steeply over time in patients without adverse events, with a statistically significant rise in patients without thrombotic events. These findings might reflect an insufficient increase in AnxA1 as a response to the excessive hyperinflammation in COVID-19. Future studies should evaluate whether hyperinflammation could be reduced through the administration of human recombinant AnxA1 or Ac2-26 peptide.

CD163 and CD206 expression define distinct macrophage subsets involved in active ANCA-associated glomerulonephritis.

INTRODUCTION: Macrophages are key players in the immunopathology of anti-neutrophil cytoplasmic antibody (ANCA) mediated-vasculitis (AAV) with glomerulonephritis (ANCA GN). Different macrophage phenotypes are expected to play distinct roles in ANCA GN. Macrophages expressing CD163 and CD206 are found in lesions associated with ANCA GN. Hence, we aimed to investigate the clinicopathological significance of CD206 and CD163 in ANCA GN in a multicenter retrospective cohort study. MATERIAL AND METHODS: Patients with ANCA-associated vasculitis, with clinical data, serum and urine samples were included from three cohorts. Serum soluble CD206 (ssCD206) and urinary soluble CD163 (usCD163) levels were measured. Human kidney tissue samples (n = 53) were stained for CD206 and CD163 using immunohistochemistry and immunofluorescence, and findings were correlated with clinical and pathological data. RESULTS: In total, 210 patients were included (i.e., ANCA GN, n = 134; AAV without GN, n = 24; AAV in remission n = 52). Increased levels of both ssCD206 and usCD163 were seen in ANCA GN. High levels of ssCD206 declined after reaching remission, however, ssCD206 did not improve the accuracy of usCD163 to detect ANCA GN. Soluble markers correlated with histopathological findings. CD163+CD206- macrophages were found in the glomerulus and may play pivotal roles in glomerulonephritis, whereas CD206+CD163- and CD206+CD163+ macrophages were located tubulointerstitially and likely play a more prominent role in ANCA-associated tubulointerstitial inflammation. In ANCA GN patients increasing levels of ssCD206 increased the risk for end-stage renal disease and mortality. CONCLUSIONS: Our results confirm and extend the notion that CD206+ and CD163+ macrophages are prominent components of the cellular infiltrate in ANCA GN. We found distinct macrophage phenotypes that may play distinct roles in the immunopathology of ANCA GN and elaborate on a potential mechanism underlying the findings of this study. usCD163 remains an excellent marker to detect active ANCA GN, whereas ssCD206 seems a more prominent marker for risk prediction.

Autoimmune Encephalitis With mGluR1 Antibodies Presenting With Epilepsy, but Without Cerebellar Signs: A Case Report.

OBJECTIVE: To describe the unique case history of a patient with mGluR1 antibodies, with mainly limbic and without cerebellar symptoms. METHODS: A 50-year-old woman initially presented with focal seizures with epigastric rising and déjà-vu sensations, next to cognitive complaints, and musical auditory hallucinations. MRI, EEG, and neuronal autoantibody tests were performed. RESULTS: EEG findings showed slow and sharp activity (sharp waves and sharp-wave-slow-wave complex) in the left temporal lobe. A test for autoantibodies was negative initially. Because of persistent symptoms, serum and CSF were tested 4 years later and found positive for mGluR1 antibodies. Treatment started with monthly IV immunoglobulins and azathioprine that was replaced by mycophenolate mofetil later. Especially cognitive symptoms and hallucinations did not respond well to the treatment. During treatment, mGluR1 antibodies remained present in CSF. DISCUSSION: Whereas cerebellar symptoms are present in 97% of mGluR1-positive cases, our patient presented without ataxia. Therefore, we suggest that the clinical presentation of patients with mGluR1 antibodies is probably more diverse than previously described. Testing for mGluR1 antibodies should be considered in patients with limbic encephalitis and epilepsy, especially when negative for more common antibodies.

The Role of Autoantibodies in the Diagnosis of Autoimmune Liver Disease: Lessons Learned from Clinical Practice.

BACKGROUND: Primary biliary cholangitis (PBC), autoimmune hepatitis (AIH) and primary sclerosing cholangitis (PSC) are autoimmune liver diseases associated with distinct autoantibodies. Diagnosis is based upon clinical, serological, and histopathology findings. The role of autoantibodies in the diagnosis of these autoimmune liver diseases, with the focus on PBC and AIH, will be discussed. CONTENT: When AIH or PBC is suspected, testing for multiple autoantibodies can be requested. In this mini-review, the different ways in which autoantibodies can be tested (indirect immunofluorescence and antigen-specific tests) in the context of PBC and AIH are discussed, as well as the pitfalls in interpreting the test results. SUMMARY: For appropriate interpretation of test results, an important prerequisite is that the doctor knows which test is used in the laboratory of choice and that the laboratory specialist is aware of what the doctor wants to test for. Good communication between clinician and laboratory specialist can, therefore, aid in the diagnosis of autoimmune liver diseases.

Treatment of Autoimmune Diseases with Therapeutic Antibodies: Lessons Learned from PID Patients Allow for Stratification of the Infection Risk.

Over the years, a wide variety of therapeutic antibodies has been successfully introduced in the autoimmunology clinic and many more are on the edge to follow. Many of these treatments address either a pathogenic circulating molecule or a cell-bound molecule. Whereas the former target results in neutralization of the soluble factor, the latter target either inhibits cellular function or induces selective cell death. If this targeted molecule or cell is part of the immune system, this therapy evokes a state of immunodeficiency. Knowing the exact function of the respective components enables the risk stratification for possible infectious complications in patients treated with biologics. Much of the understanding of the function of immune cells and their associated molecules, in relation to redundancy in the immune system, is derived from studies in knockout mice. However, as mice are not men in terms of their life-expectancy, their infection exposure, or the composition of their immune system, the most useful knowledge for estimating the consequence of therapeutic intervention on immune competence comes from monitoring patients. In the current chapter, we focus on patients with a primary immunodeficiency (PID) because they provide us with a unique perspective to estimate the redundancy of a certain genetic defect for overall immune competence. These patients have inborn errors of the immune system that, in general, are due to single gene defects. Depending on the immunological pathway that is defective, patients can present with different types of (opportunistic) infectious diseases, as well as other clinical manifestations. Based on selected examples, we focus in this chapter on finding parallels in the infectious risk of autoimmune patients treated with biologics and PID patients with a defect in the immunological pathway that is affected by the respective biologic. The goal is to learn from the (dis)similarities between both patient populations in terms of safety profiles of biologic treatments.

B-Cell Analysis for Monitoring Patients Undergoing B-Cell Depletion for the Treatment of Autoimmune Diseases.

B-cell depleting therapy is increasingly used in the treatment of many distinct autoimmune diseases. This not only involves remission induction therapy, but also maintenance therapy. In this respect, it is of importance to monitor composition of the B-cell compartment in the peripheral blood. This can be performed at the time of initiation of the therapy, especially in those cases in which the expected clinical effect is not achieved. If B-cells are absent, B-cell depletion may not be the best treatment option; if B-cells are present, the efficacy may be hampered by neutralizing antibodies. For monitoring B-cell recovery it is important not to just enumerate B-cells, but to also phenotype the B-cells. A phenotype of IgD-CD27++CD38++ indicates the presence of circulating plasmablasts that lack CD20 and which are therefore not sensitive for B-cell depletion with anti-CD20 biologicals. A phenotype of IgD+CD27-CD38++ on the other hand, indicates recovery from the bone marrow with transitional B-cells. This chapter will focus on B-cell analyses by flow cytometry.

Functional and Genetic Landscape of Complement Dysregulation Along the Spectrum of Thrombotic Microangiopathy and its Potential Implications on Clinical Outcomes.

INTRODUCTION: The syndromes of thrombotic microangiopathy (TMA) are diverse and represent severe endothelial damage caused by various mechanisms. The complement system plays a major role in a subset of patients with TMA, and its recognition is of clinical importance because it guides choice and duration of treatment. METHODS: We studied a well-defined cohort of patients with TMA and hypothesized that assessment of serum-induced ex vivo C5b9 formation on the endothelium and screening for rare variants in complement genes can better categorize TMA. RESULTS: Massive ex vivo C5b9 formation was found in all patients with primary atypical hemolytic uremic syndrome (n/N = 11/11) and in 59% of patients with TMA and coexisting conditions (n/N = 30/51). Massive ex vivo C5b9 formation was associated with rare genetic variants (45% [n/N = 20/44] vs. 0% [n/N = 0/21] patients with normal ex vivo C5b9 formation; P < 0.001). Massive ex vivo C5b9 formation was associated with favorable renal response to therapeutic complement inhibition in patients with TMA and coexisting conditions (86% [n/N = 12/14] vs. 31% [n/N = 5/16] of untreated patients; P < 0.001), indicating complement-mediated TMA rather than secondary disease. Among treated patients, the odds ratio for 1-year kidney survival was 12.0 (95% confidence interval 1.2-115.4). TMA recurrence was linked to rare genetic variants in all cases. Patients with normal ex vivo C5b9 formation had an acute, nonrelapsing form of TMA. CONCLUSIONS: Ex vivo C5b9 formation and genetic testing appears to categorize TMAs into different groups because it identifies complement as a driving factor of disease, with potential therapeutic and prognostic implications.