A high molecular weight chemoattractant generated from C5 by ultracentrifugation of mouse serum without activation of complement

Endocytosis of oxidized LDL and reversibility of migration inhibition in macrophage-derived foam cells in vitro. A mechanism for atherosclerosis regression?

The ability of macrophage-derived foam cells to migrate from atherosclerotic lesions represents one potential mechanism for the regression of atherosclerosis. It is, however, generally recognized that the transformation of macrophages into foam cells results in greatly reduced migrational ability. In the present study, we set out to investigate the factors affecting migratory capability in foam cell-like cells with the use of an in vitro assay. Foam cell-like cells were prepared by incubating macrophages in the presence of oxidized low density lipoprotein (LDL). The transformation to a typical foam cell morphology was demonstrated by Nile red staining (light microscopy), and the mechanisms of binding, uptake, and intracellular processing of oxidized LDL were established by colloidal gold labeling on the ultrastructural level. With the in vitro assay, the migration of these foam cell-like cells was found to be markedly inhibited compared with untreated, control macrophages. However, zymosan-activated mouse serum restored migration in oxidized LDL-treated cells to levels similar to those of control cells. Restoration of migratory capacity was accompanied by alterations in the cytoskeleton system, especially in actin arrangement.

Resistance to the Sterne strain of B. anthracis: phagocytic cell responses of resistant and susceptible mice

Inflammatory responses were compared in vivo, and host phagocytic cell functions compared in vitro, of mice resistant (CBA/J) and susceptible (A/J) to lethal infection with the Sterne strain of Bacillus anthracis. Polymorphonuclear leukocyte (PMN) and macrophage responses at the initial site of infection were slower in A/J mice than in CBA/J mice. Whereas in A/J mice, the number of PMN ultimately responding to infection was equal to, or greater than, that in CBA/J mice, fewer macrophages accumulated. A/J mice failed to clear relatively low doses of the organisms and died. In vitro, chemotactic responses to both serum- and bacteria-derived attractants were similar for macrophages from A/J and CBA/J mice but were reduced for PMN from A/J mice. PMN and macrophages from the two mouse strains phagocytosed and killed spores in vitro to a similar extent, although killing by A/J PMN could be blocked by prior uptake of large numbers of killed spores. Thus susceptibility to lethal infection with Sterne strain correlated with the delayed influx (PMN) and reduced accumulation (macrophages) of phagocytes at the initial site of infection, but not with defective in vitro uptake or killing of spores.

Fifth component of complement (C5)-derived high-molecular-weight macrophage chemotactic factor in normal guinea pig serum

Normal guinea pig serum contain a chemotactic factor(s) for macrophages. As the chemotactic activity in the serum was absorbed by an anti-C5 antibody affinity column but not by the anti-C3 or anti-macrophage chemotactic factor from skin-1 (MCFS-1) affinity column, the major chemotactic factor in the serum was postulated to be C5-derived. This chemotactic factor, which was a heat-labile molecule with an apparent molecular weight of 150,000 (by gel filtration) and lacked vascular permeability activity, was distinct from the C5a-like anaphylatoxins. Using a combination of a Boyden chamber assay and a morphological polarization assay for the macrophage chemotaxis, it was revealed that this chemotactic factor was latent in plasma and could be activated by incubation for 30 min at 37 degrees C in the presence of a sufficient amount of Ca ion (5 mM) concomitant or not concomitant with the clot formation of the plasma. Precursor of MCFS-1 in plasma was not activated during coagulation.

EDTA-resistant activation of the terminal route of mouse complement after partial precipitation of serum with polyethylene glycol

A new type of activation of the terminal route of complement is described. It occurs in precipitates of mouse serum prepared with a critical amount of polyethylene glycol. The activation proceeds in the presence of 10 mM EDTA and in the absence of C1q and functional C2, C3, C4 and factor B, which suggests that it is classical and alternative pathway-independent. The activation is demonstrated by the generation of both thermo-labile haemolytic and thermo-stable chemotactic activity. For both activities C5 seems to be essential. The haemolytic activity does not show species restriction towards sheep erythrocytes, which suggests a similarity with C56-initiated (reactive) but not with (S)C5-9-mediated (deviated) haemolysis. The identity of the haemolytic complex and the chemoattractant and the possible use of the new activation for the functional analysis of the mouse terminal complement route will be the subject of further study.