Navigating the diagnostic maze: A case presentation of C1q vasculitis mimicking hypocomplementemic urticarial vasculitis in a patient with systemic lupus erythematosus.

In rare instances, patients with SLE may exhibit atypical clinical manifestations, such as Hypocomplementemic Urticarial Vasculitis, which can pose diagnostic challenges. Here, we present a case report of a 28-year-old female with a history of SLE with lupus nephritis clase IV who developed HUV-like symptoms, ultimately leading to a diagnosis of C1q Vasculitis. This case underscores the importance of considering C1q Vasculitis in SLE patients presenting with HUV-like features and highlights Rituximab as a promising therapeutic option for managing this rare condition.

C1qa deficiency in mice increases susceptibility to mouse hepatitis virus A59 infection.

BACKGROUND: Mouse hepatitis virus (MHV) A59 is a highly infectious pathogen and starts in the respiratory tract and progresses to systemic infection in laboratory mice. The complement system is an important part of the host immune response to viral infection. It is not clear the role of the classical complement pathway in MHV infection. OBJECTIVES: The purpose of this study was to determine the importance of the classical pathway in coronavirus pathogenesis by comparing C1qa KO mice and wild-type mice. METHODS: We generated a C1qa KO mouse using CRISPR/Cas9 technology and compared the susceptibility to MHV A59 infection between C1qa KO and wild-type mice. Histopathological and immunohistochemical changes, viral loads, and chemokine expressions in both mice were measured. RESULTS: MHV A59-infected C1qa KO mice showed severe histopathological changes, such as hepatocellular necrosis and interstitial pneumonia, compared to MHV A59-infected wild-type mice. Virus copy numbers in the olfactory bulb, liver, and lungs of C1qa KO mice were significantly higher than those of wild-type mice. The increase in viral copy numbers in C1qa KO mice was consistent with the histopathologic changes in organs. These results indicate that C1qa deficiency enhances susceptibility to MHV A59 systemic infection in mice. In addition, this enhanced susceptibility effect is associated with dramatic elevations in spleen IFN-γ, MIP-1 α, and MCP-1 in C1qa KO mice. CONCLUSIONS: These data suggest that C1qa deficiency enhances susceptibility to MHV A59 systemic infection, and activation of the classical complement pathway may be important for protecting the host against MHV A59 infection.

Bone marrow transplantation from a human leukocyte antigen-mismatched unrelated donor in a case with C1q deficiency associated with refractory systemic lupus erythematosus.

Human C1q deficiency is frequently associated with systemic lupus erythematosus (SLE), which requires long-term systemic corticosteroid administration. We report the case of a 12-year-old female patient with C1q deficiency presenting with intractable SLE who successfully underwent bone marrow transplantation from a human leukocyte antigen (HLA)-mismatched unrelated donor with an immunosuppressive conditioning regimen based on fludarabine, melphalan, and anti-thymocyte globulin. She developed Grade I graft-versus-host disease, but did not have any transplantation-related morbidity. Complete donor chimerism has been maintained for 2 years after transplantation, leading to the restoration of C1q levels and the resolution of SLE symptoms. Normal C1q mRNA expression was observed in CD14 + cells. Hematopoietic stem cell transplantation from an HLA-mismatched donor is a feasible treatment for patients with C1q deficiency with refractory SLE that is dependent on systemic corticosteroid treatment who do not have an HLA-matched donor.

Serum complement C1q level is associated with acute coronary syndrome.

BACKGROUND AND OBJECTIVES: The complement system plays an important role in the development of acute coronary syndrome (ACS). Complement C1q is an important initial component of the classical complement pathway and closely related to many chronic inflammatory diseases, including atherosclerosis (AS). We aimed to determine whether there was association between serum complement C1q and the severity of coronary stenosis. SUBJECTS AND METHODS: 320 patients who underwent coronary arteriography (CAG) were stratified into non-ACS group (control group, n = 74), unstable angina group (UA group, n = 197) and acute myocardial infarction group (AMI group, n = 49) according to the severity of coronary stenosis and clinical manifestations. The severity of coronary stenosis was represented in Gensini score, and serum complement C1q level was compared using immunity transmission turbidity among three groups. RESULTS: The level of complement C1q in AMI group was lower significantly than control group and UA group (P < 0.05), but there was no correlation between serum complement C1q and Gensini score (ß=-0.086, P = 0.125). In nitrate-taking patients, serum complement C1q had a negative association with Gensini score (r=-0.275, P = 0.001), and in non-smokers, there was also a negative correlation (ß=-0.159, P = 0.036). After calibrating smoking, drinking or statins, the serum complement C1q levels of control group, UA group and AMI group decreased in sequence (P <  0.05). Logistic regression analysis showed that the decreasing of serum complement C1q was an unfavorable factor for acute myocardial infarction (OR=0.984, 95 %CI=0.972∼0.997, P = 0.015) and for ACS (OR=0.984, 95 %CI=0.971∼0.984, P = 0.025) in drinking patients. Regrettably, ROC curve suggested that the accuracy in diagnosing coronary atherosclerotic heart disease by serum complement C1q was low (AUC=0.568, 95 %CI= 0.492-0.644, P = 0.076, sensitivity 73.6 %, specificity 58.1 %). CONCLUSION: Serum complement C1q in ACS patients, in particular AMI patients, showed lower level. This finding suggests further decrease of complement C1q level in ACS patients may be a contributory factor to instability or rupture of atherosclerotic plaques. Combined with other clinical indicators, it can be helpful to predict the risk and severity of coronary stenosis.

Secondary C1q Deficiency in Activated PI3Kδ Syndrome Type 2.

Monogenic forms of vasculitis are rare but increasingly recognized. Furthermore, genetic immunodeficiency is increasingly associated with inflammatory immune dysregulatory features, including vasculitis. This case report describes a child of non-consanguineous parents who presented with chronic digital vasculitis early in life, is of short stature, has facial dysmorphia, immunodeficiency (low serum IgA, high serum IgM), recurrent bacterial infections, lymphoproliferation, absence of detectable serum C1q, and low classical complement pathway activity. We identified a previously reported de novo heterozygous pathogenic splice mutation in PIK3R1 (c.1425 + 1G > A), resulting in the skipping of exon 11 of the p85α subunit of phosphatidylinositol 3-kinase and causing activated PI3Kδ syndrome type II (APDS2). This explained the phenotype, with the exception of digital vasculitis and C1q deficiency, which have never been described in association with APDS2. No mutations were identified in C1QA, B, or C, their promoter regions, or in any other complement component. Functional studies indicated normal monocytic C1q production and release, suggesting that the observed C1q deficiency was caused by peripheral consumption of C1q. Since C1q deficiency has never been associated with APDS2, we assessed C1q levels in two unrelated patients with genetically confirmed APDS2 and confirmed C1q deficiency in those two cases as well. This observation suggests C1q deficiency to be an inherent but previously unrecognized feature of APDS2. We speculate that the consumption of C1q is driven by increased apoptotic bodies derived from immune cellular senescence, combined with elevated IgM production (both inherent features of APDS2). Secondary C1q deficiency in APDS2 may further contribute to immunodeficiency and could also be associated with inflammatory immune dysregulatory phenotypes, such as the digital vasculitis observed in our case.

Monogenic interferonopathies: Phenotypic and genotypic findings of CANDLE syndrome and its overlap with C1q deficient SLE.

OBJECTIVE: To report the clinical and genetic features of the first cases of chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperature (CANDLE) syndrome in an Arab population and to compare them with patients of C1q deficient systemic lupus erythematosus (SLE). MATERIALS AND METHODS: This is a retrospective case series of patients with CANDLE syndrome and C1q deficient SLE seen at a single tertiary hospital. Medical records were reviewed for demographic data, clinical and laboratory features, histopathology and imaging findings, and response to therapeutic intervention. Descriptive data were summarized. RESULTS: Three patients from unrelated families fulfilled the clinical manifestations of CANDLE syndrome. The disease onset was within the first 4 months of age. Two patients had uncommon features including uveitis, pulmonary involvement, aseptic meningitis and global delay. Skin biopsy showed heterogeneous findings. Genomic DNA screening was homozygous for mutation in PSMB8, (NM_004159.4:c.212C>T, p.T71M) in one patient and inconclusive for the other two patients. The comparison group was three patients with familial C1q deficient SLE from three unrelated families, who were born to consanguineous parents with at least one affected sibling. They presented with extensive mucocutaneous lesions, discoid rash and scarring alopecia. They required frequent admissions due to infections. CONCLUSION: This is the first report of CANDLE syndrome in an Arab population; our patients had heterogeneous phenotypic and genetic features with overlap manifestations with C1q deficient SLE. Both are monogenic interferonopathies. However, C1q deficient SLE had more systemic inflammatory disease.

Systemic lupus erythematosus with C1q deficiency: treatment with fresh frozen plasma.

Treatment and outcome of systemic lupus erythematosus (SLE) in C1q deficient patients are rarely reported. The aim of this report is to share our experience about the course of management of three cases diagnosed as SLE with C1q deficiency, in light of present literature. Initial and dominant complaints of three cases from two different families were cutaneous manifestations. One patient was also diagnosed with arthritis and thrombocytopenia. Antinuclear antibody was positive in all cases, whereas anti-dsDNA was negative with normal levels of complement C3, C4 and decreased CH50 activity. C1QA gene of two patients had homozygous nonsense mutation (c.622 > T/p.Gln208Ter). Previously, all of them had been treated with steroids, hydroxychloroquine and methotrexate or azathioprine. It was learned that they had responded only to high dosage prednisolone and their symptoms flared up during dosage reduction even under methotrexate or azathioprine. All symptoms of all three cases improved by daily fresh frozen plasma (FFP) infusions, and once cutaneous lesions subsided, the infusions were reduced to a frequency that would prevent the flare up of the symptoms. Literature search revealed seven reports on fresh frozen plasma treatment in SLE with C1q deficient patients. In this report, it is concluded that severe cutaneous lesions, as seen in these C1q deficient SLE patients, cannot be controlled with conventional immunosuppressive treatment. Instead, regular fresh frozen plasma infusions are proposed as a more reasonable method of treatment.

MafB is a critical regulator of complement component C1q.

The transcription factor MafB is expressed by monocytes and macrophages. Efferocytosis (apoptotic cell uptake) by macrophages is important for inhibiting the development of autoimmune diseases, and is greatly reduced in Mafb-deficient macrophages. Here, we show the expression of the first protein in the classical complement pathway C1q is important for mediating efferocytosis and is reduced in Mafb-deficient macrophages. The efferocytosis defect in Mafb-deficient macrophages can be rescued by adding serum from wild-type mice, but not by adding serum from C1q-deficient mice. By hemolysis assay we also show that activation of the classical complement pathway is decreased in Mafb-deficient mice. In addition, MafB overexpression induces C1q-dependent gene expression and signals that induce C1q genes are less effective in the absence of MafB. We also show that Mafb-deficiency can increase glomerular autoimmunity, including anti-nuclear antibody deposition. These results show that MafB is an important regulator of C1q.

Renal manifestations in hypocomplementic urticarial vasculitis syndrome: Is it a distinct pathology?

Hypocomplementic urticarial vasculitis syndrome (HUVS) is an autoimmune disease characterized by recurrent urticaria, arthritis, and glomerulonephritis (GN). Anti-C1q antibody is the marker of HUVS together with low levels of classical pathway complements which are C2, C3, C4, and C1q. We report a case of a 6-year-old boy who presented with episodes of rashes, injected conjunctiva, abdominal pain, and arthritis, diagnosed as HUVS. He had low C3, low CH50, normal C4, and positive C1q antibody. His urinalysis showed intermittent microscopic hematuria only. One year later, his laboratories showed persistent low C3 and positive Anti-ds DNA. The urinalysis showed hematuria, pyuria, and nephrotic-range proteinuria. Urine protein to creatinine ratio was 101.8 h mg/mmol. Kidney biopsy showed mesangioproliferative GN consistent with the diagnosis of HUVS. The patient was treated initially with prednisolone then azathioprine was added to the regimen. He showed good response with the disappearance of hematuria and proteinuria. Nine months later, he had no skin rashes with normal urinalysis and normal anti-ds DNA antibody. We report a case with HUVS and GN with positive anti-dsDNA antibody that revealed good response to combination of immunosuppressive therapy.

IgG3-antigen complexes are deposited on follicular dendritic cells in the presence of C1q and C3.

IgG3, passively administered together with small proteins, induces enhanced primary humoral responses against these proteins. We previously found that, within 2 h of immunization, marginal zone (MZ) B cells capture IgG3-antigen complexes and transport them into splenic follicles and that this requires the presence of complement receptors 1 and 2. We have here investigated the localization of IgG3 anti-2, 4, 6-trinitrophenyl (TNP)/biotin-ovalbumin-TNP immune complexes in the follicles and the involvement of classical versus total complement activation in this process. The majority (50-90%) of antigen inside the follicles of mice immunized with IgG3-antigen complexes co-localized with the follicular dendritic cell (FDC) network. Capture of antigen by MZ B cells as well as antigen deposition on FDC was severely impaired in mice lacking C1q or C3, and lack of either C1q or C3 also impaired the ability of IgG3 to enhance antibody responses. Finally, IgG3 efficiently primed for a memory response against small proteins as well as against the large protein keyhole limpet hemocyanine.

Anatomical and Behavioral Investigation of C1ql3 in the Mouse Suprachiasmatic Nucleus.

Many biochemical, physiological, and behavioral processes such as glucose metabolism, body temperature, and sleep-wake cycles show regular daily rhythms. These circadian rhythms are adjusted to the environmental light-dark cycle by a central pacemaker located in the suprachiasmatic nucleus (SCN) in order for the processes to occur at appropriate times of day. Here, we investigated the expression and function of a synaptic organizing protein, C1QL3, in the SCN. We found that C1ql3 is robustly expressed in the SCN. C1ql3 knockout mice have a reduced density of excitatory synapses in the SCN. In addition, these mice exhibited less consolidated activity to the active portions of the day and period lengthening following a 15-minute phase-delaying light pulse. These data identify C1QL3 as a signaling molecule that is highly expressed in SCN neurons, where it contributes to the formation and/or maintenance of glutamatergic synapses and plays a role in circadian behaviors, which may include circadian aftereffects.

C1q-Dependent Dendritic Cell Cross-Presentation of In Vivo-Formed Antigen-Antibody Complexes.

Dendritic cells (DCs) are specialized in Ag engulfment via a wide variety of uptake receptors on their cell surface. In the present study we investigated Ag uptake and presentation of in vivo-formed Ag-Ab complexes by i.v. injecting mice with Ag-specific Abs followed by the cognate Ag. We show by this natural Ab-mediated Ag targeting system that uptake by splenic APC subsets is severely hampered in mice lacking complement factor C1q (C1qa-/-). Moreover, no detectable Ag cross-presentation by CD8α+ DCs from C1qa-/- mice was found. On the contrary, Ag uptake was not hampered by APCs in FcγRI/II/III/IV-deficient (FcγR quadruple-/-) mice, and the cross-presentation ability of CD8α+ DCs was not affected. In conclusion, we show that C1q rather than FcγRs controls the Ab-mediated Ag uptake and its presentation by spleen APC subsets to T cells.

Cell-specific deletion of C1qa identifies microglia as the dominant source of C1q in mouse brain.

BACKGROUND: The complement cascade not only provides protection from infection but can also mediate destructive inflammation. Complement is also involved in elimination of neuronal synapses which is essential for proper development, but can be detrimental during aging and disease. C1q, required for several of these complement-mediated activities, is present in the neuropil, microglia, and a subset of interneurons in the brain. METHODS: To identify the source(s) of C1q in the brain, the C1qa gene was selectively inactivated in the microglia or Thy-1+ neurons in both wild type mice and a mouse model of Alzheimer's disease (AD), and C1q synthesis assessed by immunohistochemistry, QPCR, and western blot analysis. RESULTS: While C1q expression in the brain was unaffected after inactivation of C1qa in Thy-1+ neurons, the brains of C1qa FL/FL :Cx3cr1 CreERT2 mice in which C1qa was ablated in microglia were devoid of C1q with the exception of limited C1q in subsets of interneurons. Surprisingly, this loss of C1q occurred even in the absence of tamoxifen by 1 month of age, demonstrating that Cre activity is tamoxifen-independent in microglia in Cx3cr1 CreERT2/WganJ mice. C1q expression in C1qa FL/FL : Cx3cr1 CreERT2/WganJ mice continued to decline and remained almost completely absent through aging and in AD model mice. No difference in C1q was detected in the liver or kidney from C1qa FL/FL : Cx3cr1 CreERT2/WganJ mice relative to controls, and C1qa FL/FL : Cx3cr1 CreERT2/WganJ mice had minimal, if any, reduction in plasma C1q. CONCLUSIONS: Thus, microglia, but not neurons or peripheral sources, are the dominant source of C1q in the brain. While demonstrating that the Cx3cr1 CreERT2/WganJ deleter cannot be used for adult-induced deletion of genes in microglia, the model described here enables further investigation of physiological roles of C1q in the brain and identification of therapeutic targets for the selective control of complement-mediated activities contributing to neurodegenerative disorders.

Pericytes and immune cells contribute to complement activation in tubulointerstitial fibrosis.

We have examined the pathogenic role of increased complement expression and activation during kidney fibrosis. Here, we show that PDGFRß-positive pericytes isolated from mice subjected to obstructive or folic acid injury secrete C1q. This was associated with increased production of proinflammatory cytokines, extracellular matrix components, collagens, and increased Wnt3a-mediated activation of Wnt/ß-catenin signaling, which are hallmarks of myofibroblast activation. Real-time PCR, immunoblots, immunohistochemistry, and flow cytometry analysis performed in whole kidney tissue confirmed increased expression of C1q, C1r, and C1s as well as complement activation, which is measured as increased synthesis of C3 fragments predominantly in the interstitial compartment. Flow studies localized increased C1q expression to PDGFRß-positive pericytes as well as to CD45-positive cells. Although deletion of C1qA did not prevent kidney fibrosis, global deletion of C3 reduced macrophage infiltration, reduced synthesis of C3 fragments, and reduced fibrosis. Clodronate mediated depletion of CD11bF4/80 high macrophages in UUO mice also reduced complement gene expression and reduced fibrosis. Our studies demonstrate local synthesis of complement by both PDGFRß-positive pericytes and CD45-positive cells in kidney fibrosis. Inhibition of complement activation represents a novel therapeutic target to ameliorate fibrosis and progression of chronic kidney disease.

Features of 847 Childhood-Onset Systemic Lupus Erythematosus Patients in Three Age Groups at Diagnosis: A Brazilian Multicenter Study.

OBJECTIVE: To evaluate demographic data and clinical and laboratory features at disease diagnosis in 3 different age groups of childhood-onset systemic lupus erythematosus (SLE): group A, early-onset (<6 years); group B, school age (≥6 to <12 years); and group C, adolescent (≥12 to <18 years). METHODS: This was a Brazilian multicenter cohort retrospective study in 10 pediatric rheumatology centers, including 847 childhood-onset SLE patients. RESULTS: Patients were divided into 3 groups: group A with 39 patients (4%), group B with 395 patients (47%), and group C with 413 patients (49%). Of 39 childhood-onset SLE patients in group A, 3 (8%) were ages <2 years, 4 (10%) were ≥2 to <3 years, and 32 (82%) were ≥3 and <6 years. A total of 74 childhood-onset SLE patients were analyzed for C1q levels, and complete C1q deficiency was observed in 3 of 74 patients (4%), all in group A. Groups were similar regarding high frequencies of female sex, nephritis, neuropsychiatric involvement, Systemic Lupus Erythematosus Disease Activity Index 2000 score ≥8, autoantibody profile, elevated acute phase proteins, and low complement levels (P > 0.05). However, the frequency of fever (78% versus 61% versus 47%; P < 0.0001), hepatomegaly (42% versus 29% versus 14%; P < 0.0001), splenomegaly (28% versus 12% versus 4%; P < 0.0001), and discoid lupus (13% versus 4% versus 4%; P = 0.020) was significantly higher in group A compared to groups B and C. The frequency of weight loss >2 kg (19% versus 28% versus 36%; P = 0.017), photosensitivity (34% versus 41% versus 51%; P = 0.006), leukopenia <4,000/mm3 (14% versus 25% versus 30%; P = 0.048), and lymphopenia <1,500/mm3 (22% versus 41% versus 47%; P = 0.011) was significantly lower in group A. CONCLUSION: Our large multicenter study identified the finding that the initial appearance of childhood-onset SLE is characterized by comparable high frequency of internal organ involvement and some distinct clinical and laboratory features in early-onset and adolescent groups.

C1q Modulates the Response to TLR7 Stimulation by Pristane-Primed Macrophages: Implications for Pristane-Induced Lupus.

The complement component C1q is known to play a controversial role in the pathogenesis of systemic lupus erythematosus, but the underlying mechanisms remain poorly understood. Intraperitoneal injection of pristane induces a lupus-like syndrome whose pathogenesis implicates the secretion of type I IFN by CD11b(+) Ly6C(high) inflammatory monocytes in a TLR7-dependent fashion. C1q was also shown to influence the secretion of IFN-α. In this study, we explored whether C1q deficiency could affect pristane-induced lupus. Surprisingly, C1qa(-/-) mice developed lower titers of circulating Abs and milder arthritis compared with the controls. In keeping with the clinical scores, 2 wk after pristane injection the peritoneal recruitment of CD11b(+) Ly6C(high) inflammatory monocytes in C1qa(-/-) mice was impaired. Furthermore, C1q-deficient pristane-primed resident peritoneal macrophages secreted significantly less CCL3, CCL2, CXCL1, and IL-6 when stimulated in vitro with TLR7 ligand. Replenishing C1q in vivo during the pristane-priming phase rectified this defect. Conversely, pristane-primed macrophages from C3-deficient mice did not show impaired cytokine production. These findings demonstrate that C1q deficiency impairs the TLR7-dependent chemokine production by pristane-primed peritoneal macrophages and suggest that C1q, and not C3, is involved in the handling of pristane by phagocytic cells, which is required to trigger disease in this model.