Morphological evidence for the ability of eosinophils to damage antibody-coated schistosomula

Schistosomula of Schistosoma mansoni were incubated with preparations from human peripheral blood containing up to 98% eosinophils, in the presence or absence of anti-schistosomular antibody. It was found that there was a correlation between damage to the schistosomula, as judged by phase-contrast microscopy, and release of 51chromium from labelled organisms. The proportion of schistosomula showing damage did not increase over the times tested (two to six hours), but the release of chromium was progressive over the same period. This suggested that the chromium within damaged schistosomula was not all released immediately after the initial damage. A small proportion of the schistosomula appeared not to be susceptible to antibody-dependent, eosinophil-mediated damage. Antibody alone, in the absence of eosinophils, did not have any detectable damaging effect. Electron microscopy showed that, in the presence of antibody, the interaction between eosinophils and schistosomula, which results in damage to the schistosomula, is initiated by an intimate contact between the eosinophils and the schistosomular surface.