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 appears pentalaminar. By freeze-fracture techniques, modified attachment areas are found. The edge zone often appears as a single strand of intramembrane particles (IMP) on the P2 face and as a groove on the E2 face. The edge zone may also have large dicontinuities, in which case it no longer separates membrane faces of unequal IMP density from one another. In addition, the IMP 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. Eosinophil plasma membranes are seen adhering to a layer of electron-dense material on the parasite after the cells have been disrupted by pipetting. Eosinophils may adhere to the parasite surface through their discharged granule material and not by membrane fusions.