Complement component 4A protein levels are negatively related to frontal volumes in patients with schizophrenia spectrum disorders.

BACKGROUND: Excessive C4A-gene expression may result in increased microglia-mediated synaptic pruning. As C4A overexpression is observed in schizophrenia spectrum disorders (SSD), this mechanism may account for the altered brain morphology (i.e. reduced volume and cortical thickness) and cognitive symptoms that characterize SSD. Therefore, this study investigates the association of C4A serum protein levels with brain morphology and cognition, and in particular whether this association differs between recent-onset SSD (n = 69) and HC (n = 40). METHODS: Serum C4A protein levels were compared between groups. Main outcomes included total gray matter volume, mean cortical thickness and cognitive performance. Regression analysis on these outcomes included C4A level, group (SSD vs. HC), and C4A*Group interactions. All statistical tests were corrected for age, sex, BMI, and antipsychotic medication dose. Follow-up analyses were performed on separate brain regions and scores on cognitive sub-tasks. RESULTS: The group difference in C4A levels was not statistically significant (p = 0.86). The main outcomes did not show a significant interaction effect (p > 0.13) or a C4A main effect (p > 0.27). Follow-up analyses revealed significant interaction effects for the left medial orbitofrontal and left frontal pole volumes (p < 0.001): C4A was negatively related to these volumes in SSD, but positively in HC. CONCLUSION: This study demonstrated that C4A was negatively related to - specifically - frontal brain volumes in SSD, but this relation was inverse for HC. The results support the hypothesis of complement-mediated brain volume reduction in SSD. The results also suggest that C4A has a differential association with brain morphology in SSD compared to HC.

Complex medical history of a patient with a compound heterozygous mutation in C1QC.

INTRODUCTION: C1q is an essential part of the classical pathway of complement activation. Genetic deficiencies, caused by homozygous mutations in one of the C1q genes, are rare and are strongly associated with development of systemic lupus erythematosus (SLE). Here we describe a C1q-deficient patient with a compound heterozygous mutation. MATERIAL AND METHODS: Serum was analysed with enzyme-linked immunosorbent assay (ELISA) and Western blot for the presence of C1q, and DNA and RNA sequencing was performed to identify the mutations and confirm that these were located on different chromosomes. RESULTS: The medical history of the patient includes SLE diagnosis at age 11 years with cerebral involvement at age 13, various infections, osteonecrosis and hemophagocytic syndrome. Using ELISA and Western blot, we confirmed the absence of C1q in the serum of the patient. Using DNA sequencing, two mutations in the C1QC gene were identified: c.100G > A p.(Gly34Arg) and c.205C > T p.(Arg69X). With RNA sequencing we confirmed that the mutations are located on different chromosomes. DISCUSSION: The patient described in this case report has a compound heterozygous mutation in C1QC resulting in C1q deficiency.

Advanced glycation end products (AGEs) and the soluble receptor for AGE (sRAGE) in patients with type 1 diabetes and coeliac disease.

BACKGROUND AND AIMS: Advanced glycation end (AGE) products play a role in the progression of diabetic complications. Gluten-free diet (GFD) might affect AGE levels in patients who adhere to a GFD because of coeliac disease (CD). The aim of our study was to compare skin AGE levels and soluble receptor AGE levels (sRAGE) in patients with type 1 diabetes (T1DM) with (T1DM + CD) and without CD (T1DM - CD) and healthy controls. METHODS AND RESULTS: We recruited 25 T1DM + CD and 25 T1DM - CD patients, matched for age, gender, diabetes duration, and glycaemic control alongside 25 healthy controls. We collected demographic, clinical and biochemical characteristics, including skin autofluorescence (AF), sRAGE and hs-CRP levels. The duration of T1DM in patients was 30 ± 14 (+CD) and 29 ± 14 years (-CD), whereas CD duration in T1DM + CD patients was 14 ± 10 years. Skin AF levels in T1DM patients were higher compared to healthy controls (2.5 ± 0.6 versus 1.9 ± 0.4, p < 0.01) and skin AF was independently associated with age (r = 0.72, p < 0.01). sRAGE levels were higher in T1DM - CD patients compared to healthy controls (1554 ± 449 versus 1309 ± 400, p = 0.049) and independently associated with creatinine levels (r = 0.32, p < 0.01). CONCLUSION: Our study demonstrates that skin AGE and sRAGE levels are elevated in T1DM patients compared with healthy controls. No difference in skin AF or sRAGE levels between T1DM patients with or without CD were observed. The present study suggests that differences in microvascular complications between T1DM and T1DM + CD patients are not due to differences in skin AF or sRAGE levels.

Serum autoantibodies directed against transglutaminase-2 have a low avidity compared with alloantibodies against gliadin in coeliac disease.

Coeliac disease is characterized by intolerance to gliadin and related gluten components present in wheat, barley and rye. Coeliac disease patients harbour antibodies directed against alloantigens such as gliadin, but also against the autoantigen transglutaminase-2 (TG2). The type and quality of antibody responses provides insight into the underlying immune activation processes. Therefore, in this study we have analysed the avidity of the antibody response directed against the autoantigen TG2 and compared this with antibody responses against the alloantigens gliadin and Escherichia coli. We observed that the immunoglobulin (Ig)A autoantibody response directed against TG2 is of low avidity compared with the IgA response against the alloantigens gliadin and E. coli in the same patients; the same was true for IgG, both in IgA-deficient and in -sufficient coeliac patients. The observed avidities appear not to be related to disease stage, antibody levels, age or duration of exposure to gluten. In conclusion, in coeliac disease there is a clear difference in avidity of the antibody responses directed against the auto- and alloantigens, indicating different regulation or site of initiation of these responses.

CD55 expression patterns on intestinal neuronal tissue are divergent from the brain.

BACKGROUND: and objectives: In this study, we investigated how enteric plexuses protect themselves from complement mediated attack. For this purpose, the expression patterns of membrane bound complement regulatory proteins (mCRP) and their association with C3 deposition was determined. In addition, mCRP expression patterns of enteric plexuses were compared with those in the central nervous system (CNS). METHODS: Immunohistochemical stainings were performed to discriminate neuronal cells from glial cells and to detect the presence of CD46, CD55, CD59, and C3d. RNA in situ hybridisation (RISH) was used to determine the cell types that produce CD55 mRNA. RESULTS: Enteric plexuses minimally expressed CD46 whereas CD55 and CD59 were highly expressed. CD55 expression was also observed in a ring around Auerbach's plexuses which was not observed for CD46 and CD59. C3d was deposited around the plexuses but plexus cells themselves did not stain for C3d. In contrast with CNS neurones, enteric neurones were shown to express CD55 whereas enteric glial cells did not. This was confirmed with CD55 RISH. Phospholipase C mediated cleavage of CD55 demonstrated that CD55 was most likely attached to elastic fibres surrounding the plexus. Attached CD55 might protect CD55 negative glial cells from complement mediated injury during inflammatory reactions. CD55 on elastic fibres surrounding the plexuses most likely originated from enteric neuronal cells. CONCLUSION: In contrast with the CNS, enteric neurones express CD55 and enteric glial cells lack CD55 expression. CD55, produced by neuronal cells, attached to elastic fibres surrounding the plexuses is proposed to protect the CD55 negative glial cells within plexuses.

Membrane-bound complement regulatory proteins inhibit complement activation by an immunotherapeutic mAb in a syngeneic rat colorectal cancer model.

MAb-mediated immunotherapy offers a potential tool for destroying metastasizing colorectal tumor cells. Promising results have been obtained by using xenograft models. However, overexpression of membrane-bound complement regulatory proteins (mCRP) impedes complement-mediated destruction of tumor cells in vitro. mCRP operate in a species selective manner. Therefore a syngeneic animal model is needed to investigate the contribution of mCRP in mAb-mediated immunotherapy. Here we present a syngeneic rat colorectal carcinoma model, which fulfills the conditions necessary to investigate the effect of mCRP expression on mAb-mediated immunotherapy of metastases of solid tumors.CC531 rat colorectal cancer cells were injected subcapsularly into the liver of syngeneic WAG/Rij rats. Four mAb (MG1(IgG2a), MG2(IgG2a), MG3(IgG3) and MG4(2a)(IgG2a)) directed against CC531 cells, were tested for their complement activating abilities in vitro and tumor homing capacities in vivo. Only MG4(2a) was found to activate complement in vitro and home to the tumor cells in vivo. This mAb induced C3-deposition and C-mediated lysis of CC531 cells in vitro when the effects of the C-inhibitors Crry/p65 and CD59 were neutralized. This implies an important role for these mCRP in restricting the effector functions of tumor-associated mAb on these cells. Although C activation could be induced by MG4(2a) in situ on tumor tissue sections, no deposition of C3 could be found on the tumor cells positive for MG4(2a) in vivo. This suggests that complement activation in vivo was inhibited by mCRP. The results indicate the suitability of this syngeneic animal model for studying the effects of mAb immunotherapy. However, the effect of mCRP on tumor cells need to be overcome, e.g. by the use of mAb against tumor antigens and mCRP.

Cytokines affect resistance of human renal tumour cells to complement-mediated injury.

Overexpression of membrane-bound complement regulatory proteins (mCRPs) on tumour cells may hamper the effect of immunotherapy with complement-activating monoclonal antibody (MoAb). Therefore, it is important to investigate whether cytokines can downregulate the expression of mCRP on tumour cells. In this study, the effect of 10 cytokines on the expression of the mCRP CD46, CD55 and CD59 and the renal tumour-associated antigen G250/MN/CAIX on four human renal tumour cell lines and proximal tubular epithelial cells was determined by flow cytometry. In addition, it was measured whether changes in the expression of the classical pathway regulatory proteins CD55 and CD59 had an effect on C3 deposition and lysis. Interleukin-1beta (IL-1beta) consistently downregulated the expression of CD46 and CD59; IL-4 consistently downregulated the expression of CD46 and transforming growth factor-beta1, consistently downregulated the expression of both CD46 and CD55. However, treatment with IL-1beta and IL-4 also decreased the expression of G250/MN/CAIX. Changes in the expression of CD55 and CD59 were associated with changes in the amount of C3 deposited and the extent of complement-mediated lysis, respectively. This suggests that clinical immunotherapy, consisting of treatment with cytokines and MoAb, may induce either up- or downregulation of CD55 or CD59 and thus affect the effectiveness of immunotherapy with MoAb.