Partial and complete detachment of neutrophils and eosinophils from schistosomula: evidence for the establishment of continuity between a fused and normal parasite membrane.

Abstract

Neutrophils and eosinophils adhering to the surface of schistosomula of Schistosoma mansoni have been partially or completely detached with hypertonic sucrose or by pipetting. The sucrose-treated neutrophils are attached only in areas where there are pentalaminar fusions between the neutrophil and tegumental membranes, suggesting that these fusions attach the cells to the parasites. Pipetting breaks many of the attached cells. In thin section, the tegumental membrane underlying these cells is seen to be pentalaminar. By freeze-fracture techniques, modified attachment areas are found. The edge zone often appears as a single strand of intramembrane particles (IMPs) on the P2 face and as a groove on the E2 face. The edge zone may also have large discontinuities, in which case it no longer separates membrane faces of unequal IMP density from one another. In addition, the IMPs on the IMP-rich areas become aggregated and surrounded by craters in the membrane. These experiments suggest that the fusions may be the mechanism by which the parasite acquires some host membrane components on its surface. On the other hand, eosinophil plasma membranes are seen adhering to a layer of electron-dense material on the parasite after the cells have been disrupted by pipetting. This suggests that eosinophils adhere to the parasite surface through their discharged granule material and not by membrane fusions.

Role of granulocyte oxygen products in damage of Schistosoma mansoni eggs in vitro.

“…In contrast, killing of nonphagocytosable helminths such as S. mansoni schistosomula is initiated at extracellular sites of intimate contact between the PMN plasma membrane and parasite surface (39,40). PMN-mediated host defense against schistosome ova represents, however, an unusual and little-studied model of the effector function of leukocytes.…”

The adherence of human neutrophils and eosinophils to schistosomula: evidence for membrane fusion between cells and parasites.

“…An average of two to four replicas were obtained from them, but as many as six to nine replicas were examined in some experiments . * Number in parentheses represents sucrose stress experiments, each of which was done at concentrations of 0.25, 0.37, and 0.5 M sucrose (2) . $ These experiments also served as the controls for the mechanical stress experiments (2) .…”

“…There is a large variation in the number of cells adhering to schistosomula. In a typical experiment,^-10-15% of the schistosomula have no cells adhering to them, and 50% have more than 20 (2). By thin-section microscopy, the cells are seen to orient themselves with respect to the surface of the schistosomulum in such a way that the nucleus is farthest from the schistosomulum, the granules are between the nucleus and the schistosomulum, and a layer of disrupted filaments (20) is beneath the plasma membrane closest to the schistosomulum (Fig.…”

Monocytes activate eosinophils for enhanced helminthotoxicity and increased generation of leukotriene C4

“…The observation that ECEF-treated eosinophils, unlike control cells, were capable of adhering to schistosomula in the absence of antibodies [31,35] suggested that ECEF may enhance cell degranulation and that ECEF-treated eosinophils adhered to degranulation products on the larvae. These products have been shown to act as a « glue» between the eosinophil plasma membrane and the larval tegument [36]. To assess the effect of ECEF on cell degranulation, the extent of eosinophil discharge on Ab-coated schistosomula was measured by light microscopy after labelling EPa products, or by electron microscopy, by estimating the larval surface area covered by electron-dense material of eosinophil origin.…”