Impact of VSIG4 gene polymorphisms on susceptibility and functional status of rheumatoid arthritis.

The complement receptor of the immunoglobulin superfamily (CRIg, encoded by the VSIG4 gene) is a macrophage receptor involved in the clearance of immune complexes and autologous cells. Our results suggest that the VSIG4 rs1044165T allele is a risk factor for severe functional status of rheumatoid arthritis in women, possibly by affecting VSIG4 gene expression.

Phagocytosis: Our Current Understanding of a Universal Biological Process.

Phagocytosis is a cellular process for ingesting and eliminating particles larger than 0.5 µm in diameter, including microorganisms, foreign substances, and apoptotic cells. Phagocytosis is found in many types of cells and it is, in consequence an essential process for tissue homeostasis. However, only specialized cells termed professional phagocytes accomplish phagocytosis with high efficiency. Macrophages, neutrophils, monocytes, dendritic cells, and osteoclasts are among these dedicated cells. These professional phagocytes express several phagocytic receptors that activate signaling pathways resulting in phagocytosis. The process of phagocytosis involves several phases: i) detection of the particle to be ingested, ii) activation of the internalization process, iii) formation of a specialized vacuole called phagosome, and iv) maturation of the phagosome to transform it into a phagolysosome. In this review, we present a general view of our current understanding on cells, phagocytic receptors and phases involved in phagocytosis.

Hepatitis B Virus Infection Among Leprosy Patients: A Case for Polymorphisms Compromising Activation of the Lectin Pathway and Complement Receptors.

Thousands of leprosy patients not only suffer from physical deformities, but also either have or have had hepatitis B virus (HBV) coinfection. Polymorphisms of the complement system modulate susceptibility to leprosy, but genetic susceptibility to past or present HBV infection is unknown. We used sequencing and multiplex sequence-specific PCR to genotype 72 polymorphisms of seven genes (MBL2, FCN1, FCN2, FCN3, MASP1, MASP2, C3) encoding components of the lectin pathway, and two genes encoding complement receptors (CR1, VSIG4) in 190 patients, of which 74 were positive for HBsAg and/or anti-HBc (HBV+, 93.2% with a resolved infection) and 116 lepromatous patients, and 408 HBV-blood donors. In addition, we tested for levels of proteins of the lectin pathway. We found no difference between serum concentrations of mannan-binding lectin (MBL), MBL-associated serine proteins (MASP-1, MASP-2, MASP-3, MAp44), ficolin-3 (FCN-3), soluble complement receptor 1 (sCR1) and MBL mediated C4 activation, measured by ELISA or TRIFMA in up to 167 HBV+ and HBV- patients. Haplotypes lowering protein levels or encoding dysfunctional proteins increased susceptibility to HBV infection: MBL2*LYQC (OR = 3.4, p = 0.02), MASP1*AC_CC (OR = 4.0, p = 0.015) and MASP2*1C2-l (OR = 5.4, p = 0.03). Conversely, FCN1*3C2 haplotype, associated with higher gene expression, was protective (OR = 0.56, P = 0.033). Other haplotypes associated with HBV susceptibility were: MASP2*2B1-i (OR = 19.25, P = 0.003), CR1*3A (OR = 2.65, P = 0.011) and VSIG4*TGGRCG (OR = 12.55, P = 0.014). Some polymorphisms in ficolin genes associated with lower protein levels increased susceptibility to leprosy/HBV infection: FCN*1 (OR = 1.66, P = 0.029), FCN2*GGGCAC (OR = 6.73, P = 0.008), and FCN3*del_del_C (OR = 12.54, P = 0.037), and to lepromatous disease/HBV infection: FCN2*TA (OR = 2.5, P = 0.009), whereas FCN2*MAG was associated with increased FCN-2 expression and resistance against coinfection (OR = 0.29, P = 0.026). These associations were independent of demographic factors and did not increase susceptibility to leprosy per se, except MASP2*1C2-l. Associations for FCN2, FCN3, MASP1, MASP2, and VSIG4 variants were also independent of each other. In conclusion, polymorphisms compromising activation of the lectin pathway of complement increase susceptibility to HBV infection, with ficolin polymorphisms playing a major role in modulating the susceptibility among leprosy patients.

The role of variants from the innate immune system genes in tuberculosis and skin test response in a Native American population.

Native American populations show higher tuberculosis (TB) mortality and infectivity rates than non-Native populations. Variants in the innate immune system seem to have an important role on TB susceptibility. The role of some innate immune system variants in TB susceptibility and/or skin test response (PPD) were investigated in the Aché, a Native American population. Complement receptor 1 and toll like receptor 9 variants were associated with anergy to PPD and protection to TB, respectively. These findings demonstrate an important role of the innate immune system variants in TB susceptibility.

Optimization of a flow cytometric assay to evaluate the human neutrophil ability to phagocytose immune complexes via Fcγ and complement receptors.

INTRODUCTION: This study aims to optimize some experimental conditions of a flow cytometric assay to examine the human neutrophil ability to phagocytose immune complexes (ICs) via Fcγ and complement receptors (FcγR and CR, respectively). The parameters assessed were: number of cells, concentration of ICs, reaction time, pH and concentration of the Trypan Blue quenching solution. METHODS: Neutrophils were isolated from peripheral blood of healthy volunteers. Precipitated ICs composed of IgG and fluorescein isothiocyanate (FITC)-labeled ovalbumin, opsonized or not with serum complement, were used to trigger the neutrophil phagocytosis via FcγR, CR, and FcγR+CR. Fluorescence of the internalized ICs was measured by flow cytometry, after quenching the extracellular fluorescence with Trypan Blue. RESULTS: The optimal experimental conditions established for the phagocytosis assay were: 1 × 10(6) cells mL(-1) and 40 µg mL(-1) FITC-labeled ICs, incubated for 30 min, at 37°C, in 0.5 mL of reaction volume. Trypan Blue solution at 1.25 mg mL(-1) pH4.4 was the best fluorescence quencher of FITC-labeled ICs attached to the outer surface of neutrophils. DISCUSSION: The selected experimental conditions were viable to evaluate IC phagocytosis by neutrophils; they are also suitable to compare the efficiency of IC phagocytosis mediated by FcγR and CR classes of membrane receptors, alone or in combination. This method finds application in studies of (i) the receptor-specific phagocytic function of normal and pathogenic neutrophils as well as (ii) the impact of drugs and therapies on this essential effector function of neutrophils.

Influência do sistema complemento na infecção, ativação celular e alteração da permeabilidade endotelial na dengue / Influence of complement system in infection, cellular activation and alteration on endothelial cell permeability on dengue

O Sistema Complemento (SC) desempenha papel importante no controle de infecções atuando na eliminação do patógeno e na regulação da resposta imune. Contudo, uma ativação desregulada do SC gera efeitos deletérios ao hospedeiro, contribuindo para a patogênese de diversas doenças, como na Dengue. Entretanto, o envolvimento do SCna infecção pelo vírus Dengue (DENV) ainda tem vários aspectos a serem investigados. Assim, avaliamos a contribuição do SC na infecção in vitro de monócitos pelo DENV; o perfil de expressão dos Receptores de Complemento (CR) CR1, CR2,CR3, CR4, CD46, CD55 e CD59, e de moléculas de ativação nos monócitos e linfócitos T circulantes de pacientes infectados pelos DENV-1,-2 ou -4 por citometria de fluxo.Dosamos os níveis de SC5b-9 e citocinas em pacientes por ELISA. Avaliamos ainda, a contribuição da ativação do SC na permeabilidade e viabilidade endotelial, utilizando modelo in vitro de células endoteliais (CEs) pela medida da resistência elétrica transendotelial (TEER) e liberação de LDH sobrenadante de culturas. Por fim investigamos a interação DENV-2 com componentes purificados do SC por eletroforesedas proteínas. Como achados principais, observamos diminuição na frequência de monócitos CD14+ expressando CR3, CR4 e CD59 em pacientes comparado aos controles saudáveis. De forma interessante, o bloqueio do CR3 levou à diminuição em cerca de 30 por cento da infecção in vitro pelo DENV-2 em monócitos, sem alterar o fenótipo de ativação ou a ativação da caspase-1 destas células. No entanto, com o bloqueio deCR3, detectamos diminuição na produção de TNF-alfa e IFN-alfa. Não observamos diferença significativa na frequência de linfócitos T expressando CR3, CD46, CD55 eCD59 de em pacientes-Dengue-4...

DENV-2 subunit proteins fused to CR2 receptor-binding domain (P28)-induces specific and neutralizing antibodies to the Dengue virus in mice.

Domain III (DIII) of the dengue virus (DENV) envelope (E) protein induces strong neutralizing type-specific antibodies. In addition, a region near the fusion loop in domain II (DII) induces the production of cross-reactive antibodies with neutralizing potential. Thus, this study aimed to generate DENV-2 recombinant fusion proteins (i.e., rEII*EIII and rEII*EIII/NS1*) either alone or fused to 3 copies of P28, the minimum CR2-binding domain of the complement protein C3d. The 4 recombinant proteins were generated in a Drosophila melanogaster Schneider 2 (S2) cell system. The expression and secretion of the recombinant proteins were confirmed in vitro using immunofluorescence (IF) and western blot (WB) analyses. Human dengue immune serum samples recognized recombinant proteins. The immunogenicity of the 4 proteins in BALB/c mice was analyzed using ELISA, and the results revealed that the induced specific antibody response was higher in the groups of mice immunized with the P28 fusion proteins. Interestingly, although the 4 recombinant proteins were able to elicit high levels of neutralizing antibodies in BALB/c mice; no adjuvant effect was observed in terms of neutralizing antibodies in the groups immunized with proteins containing P28. Thus, ELISA and PRNT50 assays may evaluate different epitopes and responses, where ELISA showed a wider response that did not always correlate with neutralization. Furthermore, the elicited antibodies were able to recognize the immobilized E glycoprotein of DENV. All mice vaccinated with the DENV-2 recombinant proteins showed induction of higher levels of IgG1 antibodies than of IgG2a antibodies.

Rat embryonic mast cells originate in the AGM.

Mast cells originate from pluripotent hematopoietic stem cells. Two mast cell specific antibodies, mAbsAA4 and BGD6, have previously been used to identify and study committed mast cell precursors (MCcps) in the bone marrow of adult mice and rats. However, the embryonic origin of MCcps is still not known. In the present study, we identified MCcps in rat embryos using these previously characterized mast cell specific antibodies. The MCcps were found in the AGM (aorta-gonad-mesonephros) region of rat embryos at E11.5. These cells were BGD6+, CD34(+), c-kit(+), CD13(+), FcεRI(-), AA4(-) CD40(-), and Thy-1(-). By PCR the cells contained message for the α and ß subunits of FcεRI and mast cell specific proteases. In vitro, the MCcps differentiated into metachromatic mast cells. With age of gestation the percent of MCcps diminished while the percent of mast cell progenitors increased. An increased knowledge of the biology and embryonic origin of mast cells may contribute to a greater understanding of allergy, asthma, and other mast cell related diseases.

Erythrocyte invasions and receptor heterogeneity in field isolates of Nanay river basin Iquitos.

OBJECTIVE: To determine whether the requirements for sialic acid varies and whether several types of silaic acid independent receptors utilized for invasion mechanisms of fresh filed isolates collected around Nanay river basin, Iquitos. METHODS: The field isolates were cultured as described previously by Jensen and Trager and MR4 protocol with little modifications. The erythrocytes preparation and subsequent enzyme treatment was done as described previously by Sharma. with little modification. Invasion assay was performed as described previously by Sharma et al with little modification. RESULTS: The Nanay river basin isolates showed five types of invasion mechanisms or types of receptors-ligand interactions. Here we observed that an equal numbers of neuraminidase sensitive and resistant invasion receptor-ligand interaction profiles as the most common receptor-ligand invasion profiles. Neuraminidase resistance trypsin sensitive chymotrypsin sensitive (NM(R)T(S)CT(S)) invasion of receptor-ligand interaction profile was found in seven isolates, Five field isolates and one reference strain showed neuraminidase sensitive, trypsin sensitive and chymotrypsin resistant (NM(S)T(S)CT(R)) invasion of receptor-ligand interactions, six isolates including one reference strains dd2 showed neuraminidase sensitive, trypsin and chymotrypsin resistance (NM(S)T(R)CT(R)) indicating its dependence on sialic acids and independence of trypsin and chymotrypsin sensitive proteins. Four isolates showed neuraminidase sensitive, trypsin sensitive and chymotrypsin sensitive (NM(S)T(S)CT(S)) invasion of receptor-ligand interactions, seven isolates were neuraminidase resistant, trypsin sensitive and chymotrypsin resistance (NM(R)T(S)CT(R)) invasion of receptor-ligand interactions, indicating its dependence on trypsin sensitive proteins. CONCLUSIONS: The Nanay river basin isolates showed five types of invasion mechanisms or types of receptors-ligand interactions. A full understanding of theses invasion mechanisms may allow the development of novel prophylactic and therapeutic strategies that block erythrocyte receptor-ligand invasion mechanisms.

Influência do sistema complemento na imunopatogênese da infecção pelo vírus dengue / Influence of complement system in the immunopathogenesis of dengue virus infection

O Sistema Complemento (SC) consiste numa rede de proteínas altamente regulada, podendo ser ativado pelas vias alternativa, clássica e da lectina e que convergem na clivagem de C3 e formação do complexo de ataque à membrana (C5b-9). Receptores do complemento (RC), envolvidos na regulação do SC, induzem mecanismos para eliminação de patógenos e a interação das imunidades inata e adaptativa. Estudos vem indicando que uma ativação desregulada do SC contribuiria à gravidade da dengue. A infecção humana pelo vírus Dengue (DENV) é caracterizada por um amplo espectro de sintomas clínicos, variando desde uma febre branda até distúrbios hemodinâmicos, podendo evoluir para choque hipovolêmico e morte. O objetivo principal do trabalho foi investigar o envolvimento do SC na infecção natural pelo DENV, através: (i) da avaliação quanto a expressão dos RC CR1/CD35, CR2/CD21, CR4/CD11c e CD59 nos monócitos CD14+ e linfócitos T CD4+ e TCD8+ por citometria de fluxo, (ii) dosagem de quantidades plasmáticas de SC5b-9 e das citocinas/quimiocinas TNF-alfa, IFN-gamma, CCL5, CCL2 por ELISA e por fim, (iii) avaliação da influência dos componentes do SC na alteração da permeabilidade de células endoteliais (CEs) pelo ensaio de citotoxidade pela enzima LDH. Neste estudo foram incluídos 66 pacientes com infecção pelo DENV-1 ou -2 e 12 indivíduos saudáveis. Os pacientes-DENV foram agrupados segundo a nova classificação da OMS: febre do dengue sem sinais de alarme (FD Sem SA), FD com sinais de alarme (FD Com SA) e dengue grave (G). Nossos resultados demonstraram diminuição significativa na frequência de monócitos CD14+ expressando CR1/CD35, CR4/CD11c e CD59 nos pacientes-DENV comparado aos controles. Além disso, diminuição na frequência de células T CD4+ e CD8+ expressando CR1/CD35 e CR2/CD21 nos pacientes-DENV comparado aos controles. Não observamos diferenças quanto a frequência de nonócitos CD14+ expressando CR2/CD21 ou de linfócitos T CD4+ e CD8+ expressando CR4/CD11c ou CD59 entre os grupos. A quantificação plasmática das citocinas/quimiocinas revelou: (i) maiores quantidades de TNF-alfa nos pacientes FD Sem SA e FD Com SA, (ii) quantidades aumentadas de CCL2 e (iii) diminuídas de CCL5 comparados aos controles saudáveis. Por fim, (iv) a quantidade de IFN-gamma não foi diferente entre grupos de pacientes e controles. Análises de correlação entre as quantidades de citocinas e expressão dos RC revelaram que TNF-alfa foi diretamente correlacionada com a frequência de monócitos CD14+ expressando de CD59 e CR4/CD11c, enquanto que CCL2 foi inversamente correlacionada com a frequência de linfócitos TCD8+ expressando CD59Quanto a dosagem do SC5b-9, quantidades plasmáticas desta molécula foram mais elevadas nos pacientes graves e que apresentaram manifestações hemorrágicas e extravasamento plasmático comparado aqueles sem estes sintomas. A adição de plasma de pacientes com quantidades elevadas de SC5b-9 promoveu maior lise de CEs in vitro, comparado aos plasmas de pacientes com quantidades menores de SC5b-9. Desta forma, nós concluímos que na infecção pelo DENV ocorre uma modulação dos RC nos monócitos e linfócitos T de pacientes, o que poderia levar a uma alteração funcional destas células. Além disso, TNF-alfa e CCL2 poderiam estar modulando a expressão de alguns dos RC nas células. Por fim, quantidades elevadas de SC5b-9, associada a ativação do SC, estaria associada as manifestações clínicas graves e na citotoxidade de CEs. Como perspectivas, serão avaliadas as alterações funcionais das células imunes e o grau de contribuição dos componentes do SC na patogênese da dengue. Desta forma, nossos dados levam a concluir que componentes do SC contribuem à patogênese da doença.

Mechanisms of genetically-based resistance to malaria.

Malaria remains one of the most prevalent parasitoses worldwide. About 350 to 500 million febrile episodes are observed yearly in African children alone and more than 1 million people die because of malaria each year. Multiple factors have hampered the effective control of this disease, some of which include the complex biology of the Plasmodium parasites, their high polymorphism and their increasingly high resistance to antimalarial drugs, mainly in endemic regions. The ancient interaction between malarial parasites and humans has led to the fixation in the population of several inherited alterations conferring protection against malaria. Some of the mechanisms underlying protection against this disease are described in this review for hemoglobin-inherited disorders (thalassemia, sickle-cell trait, HbC and HbE), erythrocyte polymorphisms (ovalocytosis and Duffy blood group), enzymopathies (G6PD deficiency and PK deficiency) and immunogenetic variants (HLA alleles, complement receptor 1, NOS2, tumor necrosis factor-α promoter and chromosome 5q31-q33 polymorphisms).

[Fcgamma receptor polymorphisms and systemic lupus erythematosus]. / Polimorfismos de los receptores fcgamma y lupus eritematoso sistémico.

The G Immunoglobulin Fc Receptors (FcgammaR) belong to the TNFR5 receptors family, of the immunoglobulin superfamily and are widely expressed in the immune system; their function follows in importance after the complement receptors for immunocomplexes clearance. On the other hand, the systemic lupus erythematosus (SLE) is the prototype of the autoimmune diseases mediated by immunocomplexes and several studies have shown an impaired handle of these ones in part due to dysfunction of the FcgammaR. Among all types of Fcgamma receptors, the FcgammaRIIA, FcgammaRIIB, FcgammaRIIIA and FcgammaRIIIB have well characterized polymorphisms that produce an alteration in the receptor function. A number of studies have been done worldwide to probe an association between these polymorphism and SLE or some of its clinical features, among these the most important are two meta-analyses in which it is shown that the FcygammaRIIA-R131 polymorphism present a significant association with SLE susceptibility (OR: 1.3, 95% CI: 1.10-1.52), while the FcgammaRIIIA F176 polymorphism showed to be associated with lupic nephritis (OR: 1.47, 95% CI: 1.11-1.93, p = 0.006) but not with SLE susceptibility, the results in the rest of the polymorphisms studied are still contradictories.

Larrea divaricata Cav (Jarilla): production of superoxide anion, hydrogen peroxide and expression of zymosan receptors.

Larrea divaricata is a plant widely used in folk medicine in Argentina. This work aimed to study the mechanisms of decoction activity on the release of oxygen reactive species. Decoction increased the binding of zymosan-FITC and superoxide production. Cadmium decreased the superoxide production as well as malonate and barbital. Decoction decreased the release of hydrogen peroxide. Decoction increased the reduction of MTT but not when malonate and barbital were included. Together, decoction increased the expression of dectin-1 leading to increased superoxide production. It is possible that decoction increases the activity of peroxidase, and decreases the Cu, Zn-superoxide dismutase.

Superoxide anion production by neutrophils is associated with prevalent clinical manifestations in systemic lupus erythematosus.

To determine the relation between neutrophil function and the clinical characteristics of systemic lupus erythematosus (SLE), the superoxide anion (O2-) production by neutrophils, mediated by FcgammaR and FcgammaR/CR cooperation, was studied in 64 SLE patients classified according to their prevalent clinical manifestations. Three clinically distinct patterns were designated: (1) manifestations associated with the occurrence of cytotoxic antibodies (SLE-I group); (2) manifestations associated with circulating immune complexes (IC; SLE-II group), and (3) manifestations associated with IC and cytotoxic antibodies (SLE-III group). O2- production was evaluated by a lucigenin-dependent chemiluminescent assay in neutrophils stimulated with IC-IgG opsonized or not with complement. No difference in O2- production was observed when neutrophil responses from healthy controls were compared to the unclassified patients. However, when the SLE patient groups were considered, the following differences were observed: (1) SLE-I neutrophils showed lower O2- production mediated by the IgG receptor (FcgammaR) with the cooperation of complement receptors (FcgammaR/CR) than observed in the SLE-II, SLE-III, and healthy groups; (2) neutrophils from the SLE-II group showed a decreased [Formula: see text] production mediated by FcgammaR/CR compared to the SLE-III group, (3) SLE-III neutrophils produced more O(2)(-) than neutrophils from the SLE-II and control groups, and (4) CR showed inefficiency in mediating the O2- production by neutrophils from the SLE-I group. Comparative experiments on the kinetics of chemiluminescence (CL; Tmax and CLmax) disclosed differences only for the SLE-I group. Taken together, these results suggest that differences in oxidative metabolism of neutrophils mediated by FcgammaR/CR may reflect an acquired characteristic of disease associated with distinct clinical manifestations.

Expression of Fc gamma and complement receptors in monocytes of X-linked agammaglobulinaemia and common variable immunodeficiency patients.

Recently we reported that monocyte phagocytosis and chemotaxis are impaired in X-linked agammaglobulinaemia (XLA) and common variable immunodeficiency (CVI) patients. Few data exist on the in vivo expression of receptors for the constant region of immunoglobulin (IgG) (Fc gammaR) and complement receptors (CR) in these patients. The objective of this study was to investigate the expression of Fc gammaR and CR on monocytes from XLA and CVI patients and compare it to that of healthy controls. Whole blood samples were obtained from 10 patients with XLA, 12 with CVI and 18 healthy controls. Monocyte phenotype was determined by flow cytometry with gating on CD14+ cells. Surface expression of Fc gammaRI (CD64), Fc gammaRII (CD32) and Fc gammaRIII (CD16), CR1 (CD35) and CR3 (CD11b and CD18) was measured by determination of the proportion of CD14+ cells positive for each receptor and by receptor density. Compared to controls, a significantly higher percentage of CD16 and CD35+ monocytes from XLA (P = 0.002 and P = 0.007, respectively) were observed. The relative fluorescence intensity (RFI) expression of Fc gammaRII (CD32) and Fc gammaRIII (CD16) were significantly lower on CVI monocytes compared to controls (P = 0.001 and P = 0.035, respectively). XLA patients, who have a reduction of Bruton's tyrosine kinase (Btk), showed normal or increased percentages of monocytes expressing Fc gamma and complement receptors. CVI patients, who have normal expression of Btk, showed reduced expression of CD16 and CD32 on monocytes. Inefficient chemotaxis and phagocytosis, reported previously in XLA patients, could be due to defects of cytoplasmatic transduction mechanisms.

Neutrophil effector functions triggered by Fc-gamma and/or complement receptors are dependent on B-ring hydroxylation pattern and physicochemical properties of flavonols.

Tissue damage in autoimmune diseases involves excessive production of reactive oxygen species (ROS) triggered by immune complexes (IC) and neutrophil (PMN) interactions via receptors for the Fc portion of IgG (FcgammaR) and complement receptors (CR). Modulation of both the effector potential of these receptors and ROS generation may be relevant to the maintenance of body homeostasis. In the present study, the modulatory effect of four flavonols (myricetin, quercetin, kaempferol, galangin) on rabbit PMN oxidative metabolism, specifically stimulated via FcgammaR, CR or both classes of receptors, was evaluated by luminol- and lucigenin-dependent chemiluminescence assays. Results showed that flavonol inhibitory effect was not dependent on the cell membrane receptor class stimulated but related to the lipophilicity of the compounds (their apparent partition coefficient values were obtained by high-performance liquid chromatography), and was also inversely related to the number of hydroxyl groups in the flavonol B ring and the ROS-scavenger activity (assessed by the luminol--H2O2--horseradish peroxidase reaction). Under the experimental conditions the flavonols tested were not toxic to PMNs (evaluated by lactate dehydrogenase release and trypan blue exclusion) and did not interfere with IC-induced phagocytosis (evaluated by transmission electron microscopy). Our results suggested that inhibition of IC-stimulated PMNs effector functions by the flavonols tested herein was the result of cooperation of different cellular mechanisms.

Complement components, regulators and receptors are produced by human monocyte-derived dendritic cells.

Complement and dendritic cells (DCs) are essential components of innate immunity. Both participate in local inflammation and moreover have roles in the initiation of the acquired immunity response and in the maintenance of tolerance. Recent studies have demonstrated the ability of DCs to synthesize C1q, C3, Factor I, Factor B and complement receptors 3 and 4. In this study, we demonstrate that human DCs are a source of other soluble complement proteins including C1q, C4b binding protein (C4BP), C7 and C8. Complement receptors (CR)1 and the CD18 chain (common for CR3 and CR4) were also present on DCs while CR2 was not detected.

Leishmania amazonensis: multiple receptor-ligand interactions are involved in amastigote infection of human dendritic cells.

In their mammalian hosts, Leishmania are obligate intracellular parasites that reside in macrophages and dendritic cells (DCs). In the present study, we have investigated in vitro the mechanisms of entry into human DCs of Leishmania amazonensis amastigotes isolated from lesions in nude mice (Am nude). The DC infection rate with Am nude was approximately 36%, while opsonization of Am nude with normal human serum and infected human serum increased the DC infection rates to 60% and 62%, respectively. Heat inactivation and depletion of antibodies in sera brought the DC infection rate down to 40%. The DC infection rate was inhibited after pre-treatment of Am nude with heparin. We were unable to implicate mannose-fucose receptors in the uptake of Am nude by DCs. Our data suggest that the ability of L. amazonensis amastigotes to infect human DCs involves the participation of at least three multiple receptor-ligand interactions, antibodies/FcR, complement components/CR and proteoglycans/heparin-binding protein.

Knops blood group haplotypes among distinct Brazilian populations.

BACKGROUND: The Knops blood group system consists of antigens encoded by exon 29 of complement receptor 1 (CR1) gene. To better elucidate the complexity of Knops group system, the frequency of six single-nucleotide polymorphisms (SNPs) in three Brazilian populations is determined. STUDY DESIGN AND METHODS: A total of 118 individuals descendant from Europe, Asia, and Africa were studied. The genomic fragment of CR1 was amplified by polymerase chain reaction, and the SNPs and haplotypes were determined after DNA sequence analysis. RESULTS: Among the six polymorphisms characterized, one of them was described for the first time. The analysis of allele frequency showed that these six SNPs did not differ between the European and Asian groups. The African group presented a higher frequency of alleles McC(b), Sl2, and KAM+. The six polymorphisms gave origin to 12 haplotypes that were defined for the first time. The haplotypes 1 (4646A, Kn(a), McC(a), Sl1, Sl4, KAM+), 2 (4646A, Kn(a), McC(a), Sl1, KAM-), and 3 (4646A, Kn(a), McC(a), Sl2, Sl4, KAM-) are the most frequent in all populations. The H2 presents similar frequency in all populations; however, whereas the H1 presented a higher prevalence in the European and Asian groups, in the African group H3 was present in a higher prevalence. CONCLUSIONS: In this study, a new SNP substituting serine for asparagine at amino acid 1540 was identified. Moreover 12 haplotypes were identified. The differences in haplotype frequencies strongly suggest that the H1 and H2 might be the ancestral one while the H3 may have originated in Africa and may have fixed there by positive selection.

C5 modulates airway hyperreactivity and pulmonary eosinophilia during enhanced respiratory syncytial virus disease by decreasing C3a receptor expression.

Enhanced respiratory syncytial virus disease, a serious pulmonary disorder that affected recipients of an inactivated vaccine against respiratory syncytial virus in the 1960s, has delayed the development of vaccines against the virus. The enhanced disease was characterized by immune complex-mediated airway hyperreactivity and a severe pneumonia associated with pulmonary eosinophilia. In this paper, we show that complement factors contribute to enhanced-disease phenotypes. Mice with a targeted disruption of complement component C5 affected by the enhanced disease displayed enhanced airway reactivity, lung eosinophilia, and mucus production compared to wild-type mice and C5-deficient mice reconstituted with C5. C3aR expression in bronchial epithelial and smooth muscle cells in the lungs of C5-deficient mice was enhanced compared to that in wild-type and reconstituted rodents. Treatment of C5-deficient mice with a C3aR antagonist significantly attenuated airway reactivity, eosinophilia, and mucus production. These results indicate that C5 plays a crucial role in modulating the enhanced-disease phenotype, by affecting expression of C3aR in the lungs. These findings reveal a novel autoregulatory mechanism for the complement cascade that affects the innate and adaptive immune responses.