Human neutrophil migration and activation by BJcuL, a galactose binding lectin purified from Bothrops jararacussu venom.

BACKGROUND: Neutrophil migration to an inflamed site constitutes the first line of the innate immune response against invading microorganisms. Given the crucial role of endogenous lectins in neutrophil mobilization and activation, lectins from exogenous sources have often been considered as putative modulators of leukocyte function. Lectins purified from snake venom have been described as galactoside ligands that induce erythrocyte agglutination and platelet aggregation. This study evaluated human neutrophil migration and activation by C-type lectin BJcuL purified from Bothrops jararacussu venom. RESULTS: Utilizing fluorescence microscopy, we observed that biotinylated-BJcuL was evenly distributed on the neutrophil surface, selectively inhibited by D-galactose. Lectin was able to induce modification in the neutrophil morphology in a spherical shape for a polarized observed by optical microscopy and exposure to BJcuL in a Boyden chamber assay resulted in cell migration. After 30 minutes of incubation with BJcuL we found enhanced neutrophil functions, such as respiratory burst, zymozan phagocytosis and an increase in lissosomal volume. In addition, BJcuL delays late apoptosis neutrophils. CONCLUSION: These results demonstrate that BJcuL can be implicated in a wide variety of immunological functions including first-line defense against pathogens, cell trafficking and induction of the innate immune response since lectin was capable of inducing potent neutrophil activation.

Mast cell repopulation of the peritoneal cavity: contribution of mast cell progenitors versus bone marrow derived committed mast cell precursors.

BACKGROUND: Mast cells have recently gained new importance as immunoregulatory cells that are involved in numerous pathological processes. One result of these processes is an increase in mast cell numbers at peripheral sites. This study was undertaken to determine the mast cell response in the peritoneal cavity and bone marrow during repopulation of the peritoneal cavity in rats. RESULTS: Two mast cell specific antibodies, mAb AA4 and mAb BGD6, were used to distinguish the committed mast cell precursor from more mature mast cells. The peritoneal cavity was depleted of mast cells using distilled water. Twelve hours after distilled water injection, very immature mast cells could be isolated from the blood and by 48 hours were present in the peritoneal cavity. At this same time the percentage of mast cells in mitosis increased fourfold. Mast cell depletion of the peritoneal cavity also reduced the total number of mast cells in the bone marrow, but increased the number of mast cell committed precursors. CONCLUSIONS: In response to mast cell depletion of the peritoneal cavity, a mast cell progenitor is released into the circulation and participates in repopulation of the peritoneal cavity, while the committed mast cell precursor is retained in the bone marrow.

Neutrophil activation induced by the lectin KM+ involves binding to CXCR2.

The lectin KM+ from Artocarpus integrifolia, also known as artocarpin, induces neutrophil migration by haptotaxis. The interactions of KM+ with both neutrophils and the extracellular matrix depend on the lectin's ability to recognize mannose-containing glycans. In the present study, we characterized the binding of KM+ to human neutrophils and the responses stimulated by this binding. Exposure to KM+ results in cell polarization, formation of a lamellipodium, and induction of deep ruffles on the cell surface. By fluorescence microscopy, we observed that KM+ is distributed homogeneously over the cell surface. KM+/ligand complexes are rapidly internalized, reaching maximum intracellular concentrations at 120 min, and decreasing thereafter. Furthermore, KM+ binding to the surface of human neutrophils is inhibited by the specific sugars, d-mannose or mannotriose. KM+-induced neutrophil migration is inhibited by pertussis toxin as well as by inhibition of CXCR2 activity. These results suggest that the KM+ ligand on the neutrophil surface is a G protein-coupled receptor (GPCR). The results also suggest that neutrophil migration induced by KM+ involves binding to CXCR2.

The macrophage-derived lectin, MNCF, activates neutrophil migration through a pertussis toxin-sensitive pathway.

The macrophage-derived neutrophil chemotactic factor (MNCF) is a D-galactose-binding lectin that induces neutrophil migration in vitro and in vivo. Neutrophil recruitment induced by MNCF is resistant to glucocorticoid treatment and is inhibited by the lectin-specific sugar, D-galactose. In the present study, we characterized the binding of MNCF to neutrophils and the responses triggered by this binding. Exposure to MNCF resulted in cell polarization, formation of a lamellipodium, and deep ruffles on the cell surface. By confocal microscopy, we observed that MNCF was evenly distributed on the cell surface after 30 min of incubation. The labeling intensity progressively diminished with longer incubations. Internalization kinetics showed that MNCF/ligand complexes were rapidly internalized, reaching maximum intracellular concentrations at 120 min and then decreased thereafter. The binding and internalization of MNCF were selectively inhibited by D-galactose. MNCF-induced neutrophil chemotaxis was inhibited by pertussis toxin. This fact strongly suggests that the MNCF-ligand on the neutrophil surface is a G-protein-coupled receptor (GPCR), similar to receptors for well-established neutrophil attractants. Our observations on the ability of MNCF to activate neutrophils are consistent with the increasing evidence for the participation of animal lectins in the innate immune response.