The bacteriolytic and bactericidal effects of the human proteinases cathepsin B, cathepsin D, cathepsin G, and elastase were investigated. Cathepsin G and elastase were 5 to 10% as active as egg white lysozyme in the lysis of Micrococcus lysodeikticus. All four enzymes slowly lysed the lysozyme-resistant Staphylococcus aureus. The gram-negative Acinetobacter 199A was rendered sensitive to lysozyme by all of the proteinases. Only elastase caused marked proteolysis of the outer membrane, which would permit access by lysozyme to the underlying peptidoglycan. When the surface layer of regularly arranged a protein was removed, however, the outer membrane proteins became susceptible to the other proteinases. Cathepsin G, elastase, and cathepsin D were bactericidal to Acinetobacter 199A. The bactericidal activity of cathepsin D was shown to be dependent on enzymatic activity, unlike that of cathepsin G, which was related to its cationic nature.

The formation of the components of the cell envelope ofAcinetobacter sp. 199A was investigated by measuring the incorporation of [3H]leucine into protein, [14C]galactose into lipopolysaccharide, 32P into phospholipid, and [3H]diaminopimelic acid into peptidoglycan. Whereas the lipopolysaccharide and intrinsic protein of the outer membrane were stable, some of the regularly arranged surface protein, the a-protein, was lost into the growth medium. Only newly synthesized a-protein was lost. The peptidoglycan of the murein layer was also labile. Selective inhibition of the formation of individual components of the cell envelope with penicillin, chloramphenicol, and bacitracin showed that incorporation of protein into the outer membrane required the simultaneous formation of complete lipopolysaccharide. The converse was not true: protein synthesis was not required for lipopolysaccharide incorporation. Formation of the outer membrane and the murein layer proceeded independently.

SummaryA model has been developed to simulate the surface of an antibody-coated schistosomulum. It consists of a layer of agar, containing antigen (tetanus toxoid) and a chemotactic factor (ECF). Some layers were coated with human anti-tetanus immunoglobulin. The mode of adherence of human eosinophils and neutrophils to these agar layers and the subsequent degranulation of the cells exactly paralleled the interaction of these cell types with antibody-coated schistosomula ofSchistosoma mansoni. In particular, eosinophils made much more intimate contact than did neutrophils, and lysosomal enzymes were secreted extracellularly by direct fusion of granules with the plasma membrane of the cell. Biochemical evidence was also obtained for the secretion of enzymes during degranulation and the rate of enzyme release was found to be enhanced in the presence of specific antibody. This model, non-phagocytosable surface has the potential to provide basic information on the mode of action of effector cells in cell-mediated cytotoxic reactions against a wide range of parasites by incorporation of different factors into the agar layers.

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