Cleni Mara Marzocchi-Machado

Galectin-3 plays a modulatory role in the life span and activation of murine neutrophils during early Toxoplasma gondii infection.

Galectins are beta-galactoside-binding lectins involved in several biological processes and galectin-3 (Gal-3) is related to modulation of immune and inflammatory responses. This study aimed to evaluate the role of Gal-3 in the life span and biological functions of murine neutrophils during in vitro infection by virulent Toxoplasma gondii RH strain. Inflammatory peritoneal neutrophils (Nphi) from C57BL/6 wild-type (WT) and Gal-3 knockout (KO) mice were cultured in the presence or absence of parasites and analyzed for phosphatidylserine (PS) exposure and cell death using Annexin-V and propidium iodide staining, and cell viability by MTT assay. Cell toxicities determined by lactate dehydrogenase (LDH), degranulation by lysozyme release, and cytokine production were measured in Nphi culture supernatants. Phorbol myristate acetate (PMA)- or zymosan-dependent reactive oxygen species (ROS) were measured in Nphi cultures. Our results demonstrated that Gal-3 is involved in the increase of the viable Nphi number and the decrease of PS exposure and cell death following T. gondii infection. We also observed that Gal-3 downmodulates T. gondii-induced Nphi toxicity as well as Nphi degranulation regardless of infection. Furthermore, Gal-3 expression by Nphi was associated with increased levels of IL-10 in the beginning and decreased levels of TNF-alpha later on, regardless of parasite infection, as well as with decreased levels of IL-6 and increased IL-12 levels, following early parasite infection. Our results also showed that Gal-3 suppresses PMA- but not zymosan-induced ROS generation in Nphi following T. gondii infection. In conclusion, Gal-3 plays an important modulatory role by interfering in Nphi life span and activation during early T. gondii infection.

The influence of antibody functional affinity on the effector functions involved in the clearance of circulating immune complexes anti-BSA IgG/BSA.

A systematic study was carried out to investigate the role of antibody functional affinity in the capacity of immune complexes (IC) to activate the complement system and to trigger subsequently the molecular events involved in the handling of IC by providing a clearance mechanism. For this purpose, two populations of polyclonal anti-BSA IgG antibodies of different affinities were prepared, with values of 1.89x10(8) M(-1) and 4.94x10(8) M(-1). First we studied the capacity of IC formed at equivalence with both antibodies to activate the classical and the alternative pathways of human complement and the ability of the complexes to bind to erythrocyte C3b-C4b receptors (CR1; CD35). The data showed that the highest affinity antibodies were more efficient in activating complement by both pathways. However, their binding to erythrocyte CR1 was significantly lower compared to the binding of the lowest affinity IgG. Second we compared these IC in terms of their ability to stimulate the respiratory burst of neutrophils (PMN) and to induce the release of PMN lysosomal enzymes. In general, both of these PMN functions were better stimulated by the IC prepared with the IgG antibodies having a highest affinity, although the effects were variable for different IC concentrations. The suggestion to be drawn from the data is that the antibody affinity has an influence on the formation of the immune complex lattice, modulating its three-dimensional structure and the arrangement of the antibody Fc fragments, interfering with complement activation and access to the neutrophil IgG receptors. The significance of these observations for the understanding of how affinity influences the precise biological mechanism that participates in the fate of IC is discussed.

Study of quercetin-loaded liposomes as potential drug carriers: in vitro evaluation of human complement activation

Liposomes have been employed as potential drug carriers. However, after their in vivo administration, they can be destabilized by proteins of complement system, contributing to the clearance of vesicles from blood circulation. Antioxidant flavonoids such as quercetin have been reported to be beneficial to human health, but their low water solubility and bioavailability limit their enteric administration. Therefore, the development of appropriate flavonoid-carriers could be of great importance to drug therapy. The aim of the present study was to evaluate the activation of human complement system proteins by liposomes composed of soya phosphatidylcholine (SPC) and cholesterol (CHOL) or cholesteryl ethyl ether (CHOL-OET) loaded with quercetin or not. The consumption of complement, via classical (CP) and alternative (AP) pathways, by different vesicles was evaluated using a hemolytic assay and quantitative determination of iC3b and natural antibodies deposited on empty liposomal surfaces by ELISA. The main results showed that empty liposomes composed of large amounts of CHOL consumed more complement components than the others for both CP and AP. Furthermore, replacement of CHOL with CHOL-OET reduced complement consumption via both CP and AP. Incorporation of quercetin did not change CP and AP consumption. Deposition of iC3b, IgG and IgM in vesicles composed of SPC:CHOL-OET at a molar ratio of 1.5:1 was lower compared to the others. Taken together, these observations suggest that liposomes composed of SPC:CHOL-OET at a molar ratio of 1.5:1 are the most appropriate among the vesicles studied herein to be used as a drug carrier system in further investigations.

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 (

Hemolytic activity of alternative complement pathway as an indicator of innate immunity in pacu (Piaractus mesopotamicus)

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Galectin-3 is essential for reactive oxygen species production by peritoneal neutrophils from mice infected with a virulent strain of Toxoplasma gondii.

) production by neutrophils, mediated by FcγR and FcγR/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).

Effect of low-dose prednisone in vivo on the ability of complement receptor to mediate an oxidative burst in rat neutrophils

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