Propuesta de una dosis de marbofloxacina para el tratamiento de infecciones asociadas a Escherichia coli en cabras de tres semanas de vida

Se estimó una dosis de marbofloxacina (MFX) para tratar infecciones gastrointestinales asociadas a Escherichia coli en cabras de tres semanas de vida. La farmacodinamia de MFX sobre E. coli se evaluó in vitro estimando las concentraciones inhibitoria mínima (CIM), bactericida mínima (CBM) y preventiva de mutantes (CPM). Marbofloxacina se administró en cabras de tres semanas de edad por vía subcutánea a una dosis de 2 mg/kg. Los parámetros farmacocinéticos se estimaron mediante análisis no compartimental. La dosis de MFX capaz de proteger al 95% de una población se calculó considerando la distribución poblacional de los parámetros farmacocinéticos. La eficacia de MFX se evaluó con la relación entre el área bajo la curva y la CPM (ABC/CPM) con un valor de corte de 22 h. Los resultados mostraron que la dosis estimada de MFX para alcanzar la remisión clínica de infecciones gastrointestinales causadas por E. coli y prevenir la emergencia de cepas resistentes en el 95% de una población de cabras de tres semanas de vida fue de 3,179 mg/kg, que a los fines prácticos se fijó en 3,5 mg/kg.

A dose of marbofloxacin (MFX) to treat gastrointestinal infections caused by Escherichia coli in 3-week-old goats was estimated. The pharmacodynamics of MFX against E. coli was evaluated in vitro by estimation of mínimum inhibitory concentration (MIC), mínimum bactericide concentration (MBC) and mutant prevention concentration (MPC). Marbofloxacin was administered to 3-week -old goats by subcutaneous route at the dose of 2 mg/kg. The pharmacokinetic parameters were estimated by non-compartmental analysis. The dose of MFX capable to protect the 95% of population was calculated considering the population distribution of pharmacokinetic parameters. The efficacy of MFX was evaluated by the relationship between the area under curve and MPC (AUC/MPC) with a cut-off value of 22 h. The results showed that the estimated dose of MFX to reach the clinical outcome of gastrointestinal infections caused by E. coli and to prevent the bacterial resistance at the 95% of the population of 3-week-old goats was 3.179 mg/kg, which for practical reasons was fixed at 3.5 mg/kg.

Analysis of HLA-G expression in renal tissue in lupus nephritis: a pilot study.

BACKGROUND: The study aimed to investigate whether HLA-G antigen is expressed in the kidneys of patients affected by lupus nephritis (LN) and whether its detection in renal biopsies could be adopted as a marker of treatment response and prognosis. METHODS: Thirty renal biopsies from patients with LN were selected and analyzed through immunohistochemistry. Laboratory and clinical data were retrospectively collected at baseline, 6 and 12 months and at the latest clinical appointment. A number of patients (63.3%) were treated with rituximab (RTX) +/- methylprednisolone in the induction phase. The expression of HLA-G in glomeruli, tubules and infiltrating cells was examined and compared between lupus patients who achieved either complete or partial renal response and those who did not respond to treatment. RESULTS: HLA-G staining was observed in the glomeruli of 20 of 30 samples from patients with LN. The expression of the antigen was detected in podocytes, along glomerular capillary walls, on parietal glomerular epithelial cells and within the juxtaglomerular apparatus. Seventy per cent of patients whose glomeruli expressed HLA-G achieved partial or complete response at 6 months and 75% at the latest available follow up compared with 30% and 40%, respectively, of those who did not show any expression. The pattern of staining in tubules and infiltrating cells was highly variable precluding any clinical correlation. CONCLUSION: This study demonstrates that HLA-G is expressed in renal tissue in LN. Our retrospective data suggest that its expression could correlate with response to treatment.

A triglyceride-rich lipoprotein environment exacerbates renal injury in the accelerated nephrotoxic nephritis model.

Hyperlipidaemia accompanies chronic renal disease either as a consequence of the renal dysfunction or as part of generalized metabolic derangements. Under both situations, the lipid profile is characterized by accumulation of triglyceride-rich lipoproteins (TGRLs). This lipid profile is recognized as a risk factor for cardiovascular complications. Whether it may pose a risk for renal injury as well remains unclear. A hyper-TGRL state was generated in C57BL/6 mice using poloxamer-407 (P-407) and immune complex-mediated renal injury was triggered using the accelerated nephrotoxic nephritis (ANTN) model. The hyper-TGRL animals were hypersensitive to ANTN demonstrated by greater haematuria and glomerular cellularity. These changes were accompanied by increased glomerular accumulation of CD68+ macrophages. The hypersensitive response to ANTN was not seen in low-density lipoprotein receptor knock-out mice fed with a high fat diet, where triglyceride levels were lower but cholesterol levels comparable to those obtained using P-407. These data indicate that a hyper-TGRL state might be more detrimental to the kidneys than low-density lipoprotein-driven hypercholesterolaemia during immune complex-mediated nephritis. We speculate that the hyper-TGRL environment primes the kidney to exacerbated renal damage following an inflammatory insult with increased accumulation of macrophages that may play a key role in mediating the injurious effects.

The exaggerated inflammatory response in Behçet's syndrome: identification of dysfunctional post-transcriptional regulation of the IFN-γ/CXCL10 IP-10 pathway.

The mechanisms underlying the exaggerated inflammatory response in Behçet's syndrome (BS) remain poorly understood. We investigated the response of CD14(+) blood monocytes to interferon (IFN)-γ, focusing on the chemokine CXCL10. Chemokine synthesis and release were analysed at a protein and mRNA level following stimulation with IFN-γ. Findings in BS patients were compared with 25 healthy controls (HC), 15 rheumatoid arthritis (RA) and 15 systemic lupus erythematosus (SLE) disease control patients. BS monocytes produced significantly more CXCL10 protein than HC monocytes from 2 h following IFN-γ stimulation, despite equivalent quantities of mRNA, suggesting more efficient translation. This was significantly more pronounced in BS with high disease activity and in those with ocular and neurological clinical manifestations. The imbalance between CXCL10 protein and mRNA expression was not observed in either RA or SLE patients, and was not seen with other chemokines studied (CXCL9, CXCL11 and CCL2). Furthermore, BS monocytes treated with an alternative stimulant (LPS) did not show abnormal tumour necrosis factor (TNF)-α release. Sucrose density gradients to segregate monocyte CXCL10 mRNA into free RNA or polysome-associated RNA showed equal proportions in BS and HC samples, suggesting that the difference between BS and HC may be due to reduced negative control of CXCL10 translation in BS at a post-initiation level. We conclude that BS monocytes have dysfunctional post-transcriptional regulation of CXCL10 mRNA, resulting in over-expression of CXCL10 protein upon IFN-γ stimulation. As CXCL10 is a chemokine that recruits mononuclear cells, this abnormality may contribute to the exaggerated inflammatory responses that characterizes BS.

Application of age estimation methods based on teeth eruption: how easy is Olze method to use?

The development of new methods for age estimation has become with time an urgent issue because of the increasing immigration, in order to estimate accurately the age of those subjects who lack valid identity documents. Methods of age estimation are divided in skeletal and dental ones, and among the latter, Olze's method is one of the most recent, since it was introduced in 2010 with the aim to identify the legal age of 18 and 21 years by evaluating the different stages of development of the periodontal ligament of the third molars with closed root apices. The present study aims at verifying the applicability of the method to the daily forensic practice, with special focus on the interobserver repeatability. Olze's method was applied by three different observers (two physicians and one dentist without a specific training in Olze's method) to 61 orthopantomograms from subjects of mixed ethnicity aged between 16 and 51 years. The analysis took into consideration the lower third molars. The results provided by the different observers were then compared in order to verify the interobserver error. Results showed that interobserver error varies between 43 and 57 % for the right lower third molar (M48) and between 23 and 49 % for the left lower third molar (M38). Chi-square test did not show significant differences according to the side of teeth and type of professional figure. The results prove that Olze's method is not easy to apply when used by not adequately trained personnel, because of an intrinsic interobserver error. Since it is however a crucial method in age determination, it should be used only by experienced observers after an intensive and specific training.

Complement alternative pathway genetic variation and Dengue infection in the Thai population.

Dengue disease is a mosquito-borne infection caused by Dengue virus. Infection may be asymptomatic or variably manifest as mild Dengue fever (DF) to the most severe form, Dengue haemorrhagic fever (DHF). Mechanisms that influence disease severity are not understood. Complement, an integral component of the immune system, is activated during Dengue infection and the degree of activation increases with disease severity. Activation of the complement alternative pathway is influenced by polymorphisms within activation (factor B rs12614/rs641153, C3 rs2230199) and regulatory [complement factor H (CFH) rs800292] proteins, collectively termed a complotype. Here, we tested the hypothesis that the complotype influences disease severity during secondary Dengue infection. In addition to the complotype, we also assessed two other disease-associated CFH polymorphisms (rs1061170, rs3753394) and a structural polymorphism within the CFH protein family. We did not detect any significant association between the examined polymorphisms and Dengue infection severity in the Thai population. However, the minor allele frequencies of the factor B and C3 polymorphisms were less than 10%, so our study was not sufficiently powered to detect an association at these loci. We were also unable to detect a direct interaction between CFH and Dengue NS1 using both recombinant NS1 and DV2-infected culture supernatants. We conclude that the complotype does not influence secondary Dengue infection severity in the Thai population.

Mobilization studies in complement-deficient mice reveal that optimal AMD3100 mobilization of hematopoietic stem cells depends on complement cascade activation by AMD3100-stimulated granulocytes.

We reported that complement cascade (CC) becomes activated in bone marrow (BM) during mobilization of hematopoietic stem/progenitor cells (HSPCs) induced by granulocyte colony-stimulating factor (G-CSF) and C5 cleavage has an important function in optimal egress of HSPCs. In this work, we explored whether CC is involved in mobilization of HSPCs induced by the CXCR4 antagonist, AMD3100. To address this question, we performed mobilization studies in mice that display a defect in the activation of the proximal steps of CC (Rag(-/-), severe combined immune deficient (SCID), C2.Cfb(-/-)) as well as in mice that do not activate the distal steps of CC (C5(-/-)). We noticed that proximal CC activation-deficient mice (above C5 level), in contrast to distal step CC activation-deficient C5(-/-) ones, mobilize normally in response to AMD3100 administration. We hypothesized that this discrepancy in mobilization could be explained by AMD3100-activating C5 in Rag(-/-), SCID, and C2.Cfb(-/-) animals in a non-canonical mechanism involving activated granulocytes. To support this, granulocytes (i) first egress from BM and (ii) secrete several proteases that cleave/activate C5 in response to AMD3100. We conclude that AMD3100-directed mobilization of HSPCs, similarly to G-CSF-induced mobilization, depends on activation of CC; however, in contrast to G-CSF, AMD3100 activates the distal steps of CC directly at the C5 level. Overall, these data support that C5 cleavage fragments and distal steps of CC activation are required for optimal mobilization of HSPCs.

A lupus-susceptibility C57BL/6 locus on chromosome 3 (Sle18) contributes to autoantibody production in 129 mice.

Epistatic interactions between the non-autoimmune strains 129 and C57BL/6 (B6), used for generating gene-targeted animals, can induce a lupus-like disease. Genome-wide scan analyses of testcross progeny between these two strains have identified several lupus susceptibility loci, with the strongest linkage to the production of autoantibodies (auto-Abs) displayed by an interval on chromosome 1 of 129 origin (Sle16). However, the contribution of B6 loci to the lupus phenotype remained unknown. We used a congenic approach to deduce the contribution to the autoimmune traits of the B6 genomic interval on chromosome 3 (Sle18), previously shown to be linked to antinuclear Ab production. This interval, when transferred on a 129 background (a strain termed 129.B6-Sle18), promoted auto-Ab production targeting a broad spectrum of autoantigens, expansion of activated CD4(+)T and B cells and mild glomerulonephritis. Surprisingly, these immunological and serological defects were accompanied by a significant increase in the percentage of regulatory T cells (Tregs; CD4(+) Foxp3(+)). However, these cells, that expressed lower levels of Foxp3, had no impaired regulatory function when tested in vitro. These findings illustrate further the efficacy of congenic dissection for functional characterisation of individual lupus susceptibility loci and highlight the contribution of loci derived from non-autoimmune strains to the disease pathogenesis.

Shiga toxin-2 results in renal tubular injury but not thrombotic microangiopathy in heterozygous factor H-deficient mice.

Haemolytic uraemic syndrome (HUS) is characterized by microangiopathic haemolytic anaemia, thrombocytopenia and renal failure because of thrombotic microangiopathy (TMA). It may be caused by infection with Shiga toxin-producing enteropathic bacteria (Stx-associated HUS) or with genetic defects in complement alternative pathway (CAP) regulation (atypical HUS). We hypothesized that defective complement regulation could increase host susceptibility to Stx-associated HUS. Hence, we studied the response of mice with heterozygous deficiency of the major CAP regulator, factor H, to purified Stx-2. Stx-2 was administered together with lipopolysaccharide to wild-type and Cfh(+/-) C57BL/6 animals. Forty-eight hours after administration of the first Stx-2 injection all animals developed significant uraemia. Renal histology demonstrated significant tubular apoptosis in the cortical and medullary areas which did not differ between wild-type or Cfh(+/-) Stx-2-treated mice. Uraemia and renal tubular apoptosis did not develop in wild-type or Cfh(+/-) animals treated with lipopolysaccharide alone. No light microscopic evidence of TMA or abnormal glomerular C3 staining was demonstrable in the Stx-2 treated animals. In summary, Stx-2 administration did not result in TMA in either Cfh(+/-) or wild-type C57BL/6 mice. Furthermore, haploinsufficiency of factor H did not alter the development of Stx-2-induced renal tubular injury.

Identification of chromosome intervals from 129 and C57BL/6 mouse strains linked to the development of systemic lupus erythematosus.

Systemic lupus erythematosus is an autoimmune disease in which complex interactions between genes and environmental factors determine the disease phenotype. We have shown that genes from the non-autoimmune strains 129 and C57BL/6 (B6), commonly used for generating gene-targeted animals, can induce a lupus-like disease. Here, we conducted a genome-wide scan analysis of a cohort of (129 x B6)F2 C1q-deficient mice to identify loci outside the C1qa locus contributing to the autoimmune phenotype described in these mice. The results were then confirmed in a larger dataset obtained by combining the data from the C1q-deficient mice with data from previously reported wild-type mice. Both analyses showed that a 129-derived interval on distal chromosome 1 is strongly linked to autoantibody production. The B6 genome contributed to anti-nuclear autoantibody production with an interval on chromosome 3. Two regions were linked to glomerulonephritis: a 129 interval on proximal chromosome 7 and a B6 interval on chromosome 13. These findings demonstrate that interacting loci between 129 and B6 mice can cause the expression of an autoimmune phenotype in gene-targeted animals in the absence of any disrupted gene. They also indicate that some susceptibility genes can be inherited from the genome of non-autoimmune parental strains.

Complement deficiencies in humans and animals: links to autoimmunity.

Complement is involved in the pathogenesis of systemic lupus erythematosus (SLE) in multiple ways and may act as both friend and foe. Inherited homozygous deficiency of one of the earliest components of the classical pathway is strongly associated with susceptibility to the development of SLE. However, complement is also implicated in the effector inflammatory phase of the autoimmune response that characterizes the disease. A further paradox in the links between complement and SLE is the observation that autoantibodies to some complement proteins, especially to C1q, develop as part of the autoantibody response. In this chapter, the role of the complement system in SLE is reviewed and hypotheses advanced to explain the complex relationships between complement and lupus.

Prevention of C5 activation ameliorates spontaneous and experimental glomerulonephritis in factor H-deficient mice.

Membranoproliferative glomerulonephritis (MPGN) type II (dense deposit disease) is an inflammatory renal disease characterized by electron-dense deposits and complement C3 on the glomerular basement membrane. There is no effective therapy. We investigated the role of C5 activation in a model of MPGN that develops spontaneously in complement factor H-deficient mice (Cfh(-/-)). At 12 months there was a significant reduction in mortality, glomerular cellularity, neutrophil numbers, and serum creatinine levels in Cfh(-/-) mice deficient in C5. Excessive glomerular neutrophil numbers, frequently seen in patients with MPGN during disease flares, were also observed in Cfh(-/-) mice after the administration of an antiglomerular basement membrane antibody. This exaggerated injurious phenotype was absent in Cfh(-/-) mice deficient in C5 but not in Cfh(-/-) mice deficient in C6, indicating a key role for C5 activation in the induction of renal lesions. Importantly, the renal injury was completely reversed in Cfh(-/-) mice pretreated with an anti-murine C5 antibody. These results demonstrate an important role for C5 in both spontaneous MPGN and experimentally induced nephritis in factor H-deficient mice and provide preliminary evidence that C5 inhibition therapy might be useful in human MPGN type II.

Macrophages from patients with SLE and rheumatoid arthritis have defective adhesion in vitro, while only SLE macrophages have impaired uptake of apoptotic cells.

BACKGROUND: It has been suggested that defective handling of apoptotic cells by macrophages plays a key role in the development of systemic lupus erythematosus (SLE). The relative contribution of intrinsic defects and serum factors remains controversial. OBJECTIVE: To compare monocytes from SLE patients, patients with rheumatoid arthritis, and healthy controls for their ability to differentiate in vitro into macrophages and to bind/engulf apoptotic cells. METHODS: Peripheral blood derived monocytes from healthy donors or from patients with SLE or rheumatoid arthritis were allowed to differentiate into macrophages. The in vitro uptake of apoptotic cells by macrophages was evaluated by a flow cytometry assay that allowed discrimination between binding and internalisation. RESULTS: Monocytes from SLE and rheumatoid patients showed a striking defect in adherence to plastic compared with healthy donors. Absence or heat inactivation of serum resulted in a reduction in the binding and engulfment of apoptotic cells by macrophages. Macrophages from rheumatoid and SLE patients had similar percentages of apoptotic cells bound to their surface compared with normal controls. However, macrophages from SLE patients showed a significant defect in the internalisation of apoptotic cells compared with those from healthy controls, even in the presence of normal human serum. CONCLUSIONS: Monocytes from patients with SLE and rheumatoid arthritis have a similar defect in their capacity to adhere to plastic. However, only macrophages from SLE patients showed an impaired ability to engulf apoptotic cells, which indicates that an intrinsic cellular defect may be responsible for this phenomenon.

MRL/Mp CD4+,CD25- T cells show reduced sensitivity to suppression by CD4+,CD25+ regulatory T cells in vitro: a novel defect of T cell regulation in systemic lupus erythematosus.

OBJECTIVE: To investigate the hypothesis that loss of suppression mediated by peripheral CD4+,CD25+ regulatory T cells is a hallmark of systemic lupus erythematosus (SLE). METHODS: Mice of the MRL/Mp strain were studied as a polygenic model of SLE. Following immunomagnetic selection, peripheral lymphoid CD25+ and CD25- CD4+ T cells were cultured independently or together in the presence of anti-CD3/CD28 monoclonal antibody-coated beads. Proliferation was assessed by measuring the incorporation of tritiated thymidine. RESULTS: While MRL/Mp CD4+,CD25+ regulatory T cells showed only subtle abnormalities of regulatory function in vitro, syngeneic CD4+,CD25- T cells showed significantly reduced sensitivity to suppression, as determined by crossover experiments in which MRL/Mp CD4+,CD25- T cells were cultured with H-2-matched CBA/Ca CD4+,CD25+ regulatory T cells in the presence of a polyclonal stimulus. CONCLUSION: Our findings highlight a novel defect of peripheral tolerance in SLE. Identification of this defect could open new opportunities for therapeutic intervention.

Murine glomerular mesangial cell uptake of apoptotic cells is inefficient and involves serum-mediated but complement-independent mechanisms.

An increased number of apoptotic bodies have been detected in glomeruli of non-nephritic kidneys of C1q-deficient mice. In these mice an in vivo impaired uptake of apoptotic cells by peritoneal macrophages was also demonstrated. Here we investigated whether C1q plays a role in the in vitro clearance of apoptotic cells by glomerular mesangial cells. Phagocytosis was assessed using a novel flow cytometric assay that was validated by immunofluorescence studies. The uptake of apoptotic cells by mesangial cells, measured as percentage of mesangial cells ingesting apoptotic cells, was approximately 25%, 10% and 10% for a T cell lymphoma line (RMA), thymocytes and neutrophils, respectively. The uptake reached a plateau phase after 3 h, was specific for apoptotic cells and was mediated by serum but not by complement components C1q or C3. The phagocytosis of apoptotic cells was significantly inhibited by Arg-Gly-Asp-Ser (RGDS), a peptide capable of blocking the interaction of thrombospondin with CD36 or the vitronectin receptor. Pretreatment of the mesangial cells with dexamethasone (200 nm) but not with LPS increased the uptake markedly. These findings indicate that murine mesangial cells are capable of taking up syngeneic apoptotic cells, although much less efficiently than professional phagocytic cells. They also show that serum proteins other than complement components mediate the removal of apoptotic cells by murine mesangial cells in vitro.

Role of the classical pathway of complement activation in experimentally induced polymicrobial peritonitis.

The complement system and the natural antibody repertoire provide a critical first-line defense against infection. The binding of natural antibodies to microbial surfaces opsonizes invading microorganisms and activates complement via the classical pathway. Both defense systems cooperate within the innate immune response. We studied the role of the complement system in the host defense against experimental polymicrobial peritonitis using mice lacking either C1q or factor B and C2. The C1q-deficient mice lacked the classical pathway of complement activation. The factor B- and C2-deficient mice were known to lack the classical and alternative pathways, and we demonstrate here that these mice also lacked the lectin pathway of complement activation. Using inoculum doses adjusted to cause 42% mortality in the wild-type strain, none of the mice deficient in the three activation routes of complement (factor B and C2 deficient) survived (mortality of 100%). Mortality in mice deficient only in the classical pathway of complement activation (C1q deficient) was 83%. Application of further dilutions of the polymicrobial inoculum showed a dose-dependent decrease of mortality in wild-type controls, whereas no changes in mortality were observed in the two gene-targeted strains. These results demonstrate that the classical activation pathway is required for an effective antimicrobial immune defense in polymicrobial peritonitis and that, in the infection model used, the remaining antibody-independent complement activation routes (alternative and lectin pathways) provide a supporting line of defense to gain residual protection in classical pathway deficiency.

Continual low-level activation of the classical complement pathway.

There is evidence that the classical complement pathway may be activated via a "C1-tickover" mechanism, analogous to the C3-tickover of the alternative pathway. We have quantitated and characterized this pathway of complement activation. Analysis of freshly collected mouse and human plasma revealed that spontaneous C3 activation rapidly occurred with the generation of C3 fragments in the plasma. By the use of complement- and Ig-deficient mice it was found that C1q, C4, C2, and plasma Ig were all required for this spontaneous C3 activation, with the alternative complement pathway further amplifying C3 fragment generation. Study of plasma from a human with C1q deficiency before and after therapeutic C1q infusion confirmed the existence of a similar pathway for complement activation in humans. Elevated levels of plasma C3 were detected in mice deficient in complement components required for activation of either the classical or alternative complement pathways, supporting the hypothesis that there is continuous complement activation and C3 consumption through both these pathways in vivo. Blood stasis was found to stimulate C3 activation by classical pathway tick-over. This antigen-independent mechanism for classical pathway activation may augment activation of the complement system at sites of inflammation and infarction.

Reconstitution of the complement function in C1q-deficient (C1qa-/-) mice with wild-type bone marrow cells.

Besides Ab-independent and Ab-dependent activation of the complement classical pathway in host defense, C1q plays a key role in the processing of immune complexes and in the clearance of apoptotic cells. In humans, C1q deficiency leads to systemic lupus erythematosus-like symptoms in over 90% of the cases, thus making this defect a strong disease susceptibility factor. Similarly, C1q-deficient mice (C1qa-/-) develop systemic lupus erythematosus-like symptoms, such as autoantibodies and glomerulonephritis. We have previously provided evidence that C1q is produced by cells of the monocyte-macrophage lineage. In this study, we have tested whether transplantation of bone marrow cells would be sufficient to reconstitute C1q levels in C1qa-/- mice. C1qa-/- mice received a single graft of 10(7) bone marrow cells from wild-type (wt) donors after irradiation doses of 6, 7, 8, or 9 Gy. Engraftment was monitored by a Y chromosome-specific PCR and a PCR that differentiated wt from C1qa-/- genotype. Serum levels of C1q Ag and C1 function increased rapidly in the recipient mice, and titers reached normal levels within 6 wk after bone marrow transplantation. In wt mice that received C1qa-/- bone marrow, serum levels of C1q decreased constantly over time and became C1q deficient within 55 wk. These data clearly demonstrate that bone marrow-derived cells are the source of serum C1q and are competent to reconstitute normal C1q serum levels in C1q-deficient mice. Therefore, stem cell transplantation could be a therapy for patients with hereditary C1q deficiency.

Ultraviolet-radiation-induced keratinocyte apoptosis in C1q-deficient mice.

Exposure to ultraviolet B radiation is an important trigger of both systemic and cutaneous disease flares in individuals with systemic lupus erythematosus. More than 90% of individuals with homozygous C1q deficiency develop a systemic-lupus-erythematosus-like illness, which is typically associated with a severe photosensitive rash. Apoptotic, human keratinocytes have been shown in vitro to bind C1q, in the absence of antibody. These observations, together with the hypothesis that a major source of the autoantigens driving the immune response in systemic lupus erythematosus comes from apoptotic cells, led us to investigate the effects of murine C1q deficiency on ultraviolet-radiation-induced keratinocyte apoptosis in vivo. In this work, we demonstrated C1q binding to apoptotic murine keratinocytes in vitro and showed for the first time that C1q is also present on sunburn cells in vivo. In addition to C1q, we detected C3 deposition on sunburn cells in both wild-type and C1q-deficient mice, suggesting activation of the alternative pathway. Following acute ultraviolet exposure in vivo, no difference in the rate of clearance of sunburn cells was found in C1q-deficient mice from three different genetic backgrounds, compared with strain-matched wild-type controls. Furthermore, chronic ultraviolet exposure did not result in the production of autoantibodies or the development of glomerulonephritis. Our findings suggest that C1q does not play a critical role in the physiologic clearance of apoptotic murine keratinocytes in vivo.