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At least 163 records · Page 9Linked to original sources
PubMed1976

Quantitative contributions of IgG, IgM and C3 to erythrophagocytosis and rosette formation by peritoneal macrophages, and anti-opsonin activity of dextran sulfate 500.

In vitro phagocytosis by guinea pig peritoneal macrophages of immune complexes (EA) was shown to be dependent on IgG antibody in a dose-dependent fashion. C3b enhanced phagocytosis of EA at limited IgG antibody concentrations only. When IgM antibody was used for sensitization of sheep red blood cells (SRBC), phagocytosis and rosette formation did not occur in the absence of bound C3. The polyanion, dextran sulfate 500 (DS), was shown to depress both rosette formation and phagocytosis of EAIgG, C1423 and EAIgMC1423, as well as immune adherence of human group 0 erythrocytes and hemolytic activity of C3. This effect of DS was seen only when it was actually present in the incubation medium.

Animals↗
PubMed1985

A lectinlike receptor on murine macrophage cell line cells, Mm1: involvement of sialic acid-binding sites in opsonin-independent phagocytosis for xenogeneic red cells.

The recognition mechanism of xenogenic red cells by mouse macrophages was studied by using established cell lines. Approximately 30% of cell line cells Mm1 which lack la antigen, as well as of thioglycollate-induced peritoneal macrophages from SL/Am mice (TGC-M phi) could ingest unopsonized quail red cells (QRC). In contrast, an undifferentiated type of cell line, M1-, and another type of macrophage cell line, Mk1-C, possessing accessory cell activity in association with the expression of la antigen, had no phagocytic activity for QRC. Approximately 80% of Mm1 cells, as well as TGC-M phi formed rosettes with QRC, whereas M1- and Mk1-C cells did not; indicating that specific binding sites for QRC are expressed on a large portion of Mm1 and TGC-M phi but not on M1- and Mk1-C cells. No requirement of divalent cation (Mg++, Ca++) and metabolic energy was observed for rosette formation between Mm1 cells and QRC. Protease treatment of Mm1 cells eliminated the rosetting activity, whereas periodate oxidation of glycosidase treatment slightly enhanced this activity, suggesting the involvement of surface protein in binding sites of Mm1 cells. In contrast to these findings on Mm1 cells, binding components of QRC were sensitive to periodate oxidation or neuraminidase treatment but resistant to protease, suggesting that the terminal sialic acid residues of carbohydrate of QRC are recognized by Mm1 cells. Furthermore, N-acetylneuraminic acid (NeuNAc) inhibited the rosette formation and promoted the dissociation of rosettes already formed. N-Acetylneuramin lactose (Neu-NAc-Lact) was more efficient in rosette inhibition than NeuNAc. These sugars also blocked the phagocytosis of QRC by Mm1 cells but had no effect on either Fc-mediated phagocytosis or latex ingestion. These results suggest that phagocytosis of QRC by murine macrophages is mediated by protease-sensitive binding sites recognizing terminal sialic acid residues of QRC in conjunction with additional carbohydrates.

Animals↗
PubMed1994

Role of de novo protein synthesis by human mononuclear leukocytes in opsonin-independent phagocytosis.

Human peripheral blood lymphocytes or the soluble (105,000g) supernatant of the lymphocyte lysate can increase the percentage of human monocytes ingesting particulate activators of the human alternative complement pathway, e.g., rabbit erythrocytes (Chakravarti et al., J. Immunol. 137, 880, 1986). We now show that preincubation of the lymphocytes led to an increase in their augmenting ability. However, no such increase in the augmenting ability of the lymphocytes or soluble supernatant made from these lymphocytes was observed when they were preincubated and added to monocytes in the presence of cycloheximide; rather there was a significant reduction in the ingesting ability of the monocytes. Our results demonstrate that in the case of intact lymphocytes, the observed inhibition was because of (i) inhibition of de novo synthesis of protein(s) in the monocytes during their adherence and (ii) inhibition of de novo synthesis of protein(s) in the lymphocytes, possibly of a signaling molecule necessary for release of the peptide cytokine, phagocytosis-inducing factor (PIF), from the lymphocytes. However, the inhibition observed with soluble supernatant made from lymphocytes preincubated in the presence of cycloheximide was because of the above phenomenon (i) only and indicated that there was no de novo synthesis of PIF during preincubation of the lymphocytes.

Blood Proteins↗