Pentraxins in Complement Activation and Regulation

The complement is the first line of immune defense system involved in elimination of invading pathogens and dying host cells. Its activation is mainly triggered by immune complexes or pattern recognition molecules (PRMs) upon recognition against non-self or altered self-cells, such as C1q, collectins, ficolins, and properdin. Recent findings have interestingly shown that the pentraxins (C-reactive protein, CRP; serum-amyloid P component, SAP; long pentraxin 3, PTX3) are involved in complement activation and amplification via communication with complement initiation PRMs, but also complement regulation via recruitment of complement regulators, for instance C4b binding protein (C4BP) and factor H (fH). This review addresses the potential roles of the pentraxins in the complement system during infection and inflammation, and emphasizes the underlining implications of the pentraxins in the context of complement activation and regulation both under physiological and pathological conditions

Association of Chlamydia pneumoniae with coronary artery disease and its progression is dependent on the modifying effect of mannose-binding lectin

Background— The possible association between coronary artery disease (CAD) and Chlamydia pneumoniae (C pneumoniae) infection is controversial. On the basis of the recent suggestion that mannose-binding lectin (MBL) variant alleles are related to an increased risk of severe atherosclerosis, and on the in vitro interaction of MBL with C pneumoniae, we asked whether MBL might contribute to CAD in conjunction with C pneumoniae. Methods and Results— Antibodies to C pneumoniae were measured by immunofluorescence and MBL alleles were determined by polymerase chain reaction technique in samples from 210 patients with CAD and 257 healthy subjects from Hungary collected between 1995 and 1996. A higher percentage of patients with CAD were anti-C pneumoniae positive as compared with the control group (P=0.058). However, at logistic regression analysis adjusted to age, sex, and serum lipid levels, this difference was confined only to subjects carrying MBL variant alleles (P=0.035, odds ratio 2.63, [95% CI: 1.07 to 6.45]). In contrast, no significant difference was seen in those homozygous for the normal MBL allele (P=0.412). During a 65±5.8-month follow-up period, major outcomes (new myocardial infarction, and/or bypass operation or cardiovascular death) occurred in 11 C pneumoniae positive and 3 C pneumoniae negative patients. In the C pneumoniae positive group, the odds ratio of development of outcomes was 3.27 (95% CI: 1.10 to 9.71, P=0.033) in the carriers of the MBL variant alleles compared with the homozygous carriers of the normal MBL allele. Conclusions— These results indicate that infection with C pneumoniae leads mainly to the development and progression of severe CAD in patients with variation in the MBL gene

Alta frecuencia de un haplotipo susceptible del gen Mannose Binding Lectin, en las islas AnapiaSuana del lago Titicaca

We have analized the combination of variants at 4 sites of the gene MBL (mannose binding lectin) which is part of the immune system, in 19 normal individuals from the islands of Anapia-Suana in the Lake Titicaca. OnIy 3 combinations (haplotypes) were registered: LYPB, HYPA and LYPA; the proportion of the pressumed defective haplotype LYPB is 0.58 being the highest ever recorded. This haplotype is rare among European, Asian and African populations. It predisposes to infectious diseases as tuberculosis and AIDS as well as autoimmune diseases like reumatoid arthritis and lupus erithematosumo This finding lead our future efforts to elucidate the reason of this high frequency of LYPB and to determine its proportion in other islands of the Titicaca Lake.Se determinaron las combinaciones de variantes genéticas en 4 sitios del gen de la proteína asociada al sistema inmune MBL (mannose binding lectin), en 19 pobladores de las islas de AnapiaSuana del Lago Titicaca. Se encuentran solamente 3 combinaciones (haplotipos): LYFB, HYPA Y LYPA y se observa alta frecuencia (0.58) del haplotipo defectuoso LYPB en las mencionadas islas sobrepasando a otras frecuencias previamente reportadas en el mundo. Este haplotipo es poco frecuente en poblaciones europeas, asiáticas y africanas. La deficiencia sérica de LYPB predispone a infecciones como tuberculosis, VIH-1 y a enfermedades autoinmunes como artritis reumatoide y lupus eritematoso entre otras. Con estos antecedentes nuestros futuros esfuerzos se dirigirán a investigar la razón de la alta frecuencia de LYPB en estas islas y determinar la de las otras islas aledañas

Human stem cell-derived retinal epithelial cells activate complement via collectin 11 in response to stress

Abstract Age-related macular degeneration (AMD) is a major cause of blindness and is associated with complement dysregulation. The disease is a potential target for stem cell therapy but success is likely to be limited by the inflammatory response. We investigated the innate immune properties of human induced-pluripotent stem cell (iPSC)-derived RPE cells, particularly with regard to the complement pathway. We focused on collectin-11 (CL-11), a pattern recognition molecule that can trigger complement activation in renal epithelial tissue. We found evidence of constitutive and hypoxia-induced expression of CL-11 in iPS-RPE cells, and in the extracellular fluid. Complement activation on the cell surface occurred in conjunction with CL-11 binding. CL-11 has been shown to activate inflammatory responses through recognition of L-fucose, which we confirmed by showing that fucosidase-treated cells, largely, failed to activate complement. The presence of CL-11 in healthy murine and human retinal tissues confirmed the biological relevance of CL-11. Our data describe a new trigger mechanism of complement activation that could be important in disease pathogenesis and therapeutic interventions

Genetic and other factors determining mannose-binding lectin levels in American Indians: the Strong Heart Study

<p>Abstract</p> <p>Background</p> <p>Mannose-binding lectin (MBL) forms an integral part of the innate immune system. Persistent, subclinical infections and chronic inflammatory states are hypothesized to contribute to the pathogenesis of atherosclerosis. MBL gene (<it>MBL2</it>) variants with between 12 to 25% allele frequency in Caucasian and other populations, result in markedly reduced expression of functional protein. Prospective epidemiologic studies, including a nested, case-control study from the present population, have demonstrated the ability of <it>MBL2 </it>genotypes to predict complications of atherosclerosis,. The genetic control of <it>MBL2 </it>expression is complex and genetic background effects in specific populations are largely unknown.</p> <p>Methods</p> <p>The Strong Heart Study is a longitudinal, cohort study of cardiovascular disease among American Indians. A subset of individuals genotyped for the above mentioned case-control study were selected for analysis of circulating MBL levels by double sandwich ELISA method. Mean MBL levels were compared between genotypic groups and multivariate regression was used to determine other independent factors influencing <it>MBL2 </it>expression.</p> <p>Results</p> <p>Our results confirm the effects of variant structural (B, C, and D) and promoter (H and Y) alleles that have been seen in other populations. In addition, MBL levels were found to be positively associated with male gender and hemoglobin A1c levels, but inversely related to triglyceride levels. Correlation was not found between MBL and other markers of inflammation.</p> <p>Conclusion</p> <p>New data is presented concerning the effects of known genetic variants on MBL levels in an American Indian population, as well as the relationship of <it>MBL2 </it>expression to clinical and environmental factors, including inflammatory markers.</p