The role played by bacterial lipopolysaccharides (endotoxins) (LPS) in the initiation of tissue damage during bacterial infections, is well established. It is accepted that LPS is released from the invading bacteria following autolysis, and the interaction of the solubilized LPS with tissues and body fluids lead to the initiation of the physiological, pharmacological and pathological sequelae seen after infections with Gram negative bacterial. Previous studies from our laboratories have shown that the binding of LPS to membranes of RBC is markedly enhanced by heat-labile leukocyte factors2, and that leukocyte factors are also capable of activating ‘LPS’ for binding to cell surfaces. Since the ‘activation’ of LPS caused by this factor \s inhibited by protease inhibitors, it was postulated that proteases present Hn leukocytes and in inflammatory exudates may enhance tissue damage by increasing the passive sensitization of mammalian cells by LPS to subsequent lysis in the presence of antibodies and complement.

FURTHER STUDIES ON THE BACTERICIDAL AND BACTERIOLYTIC EFFECTS OF HUMAN LEUKOCYTE EXTRACTS: MODULATION BY ANTIBODIES CATIONIC PROTEINS, LYSOZYME, ANTIBIOTICS AND BY AUTOLYTIC SYSTEMS AND THE ROLE PLAYED BY SOME OF THESE FACTORS IN THE EXTRACTION OF LIPOTEICHOIC ACIDS FROM BACTERIA

A heat-stable factor present in extracts of human blood leukocytes is capable of lysing young Staphylococcusaureusat pH 5.0. Lysis is character- ized by breakdown of cell-wall components as judged by electron microscopic and biochemical analysis. The leukocyte extracts can be replaced by a variety of agents known to injure cell membranes, e.g., leukocyte cationic protein histone, polymyxin B, colimycin, phospholipase A, and lysolecithin. The mechanisms by which all these agents bring about the degradation of the sta- phylococcal walls was studied. By using ~4C-labeled cell walls devoid of cytoplasmic structures, it was demonstrated that none of the above-men- tioned agents had a direct lytic effect on purified cell walls. On the other hand, when any of these agents first interacted with intact staphylococci, a factor (presumably an autolysin) was generated that directly lysed the cell walls. Lysis of cell wails in the presence of intact staphylococci used as a source of autolysin was strongly inhibited by a variety of anionic poly- electrolytes such as heparine and liquoid. The possible role olayed by bacterial autolysins in the generation of microbial cell-wall comp~,nents capable of triggering chronic inflammation is discussed.

Human leukocyte extracts, egg white lysozyme, cationic proteins, polymyxin, colimycin, and phenol are capable of releasing lipoteichoic acids (LTA) from group A streptococci and Strep. mutans. While the extraction of LTA by phenol is optimal at pH 4.7, the release of LTA from streptococci by the other agents is optimal at pH 7.4. LTA released by all agents was found to have the same sensitizing abilities, as determined by passive hemagglutination, and to have a similar chemical composition, as shown by thin-layer chromatography and radioactive scanning. The LTA-releasing capacity of all the agents is strongly inhibited by normal human serum. The possible role played by LTA released by leukocyte factors in the pathogenesis of tissue damage during bacterial infections is discussed.

Although a mass of evidence exists which supports the etiologic relationship between group A streptococcal infections and the pathogenesis of human disease (6, 36, 49, 103, 112), our knowledge of the mechanisms involved in the initiation of the tissue lesions characteristic of the sequelae of streptococcal infection in man is far from complete. The hallmarks of the poststreptococcal sequelae in humans are the development of rheumatic fever, arthritis, glomerulonephritis, chorea and other less defined clinical manifestations. Lasegue’s dictum (68) that “acute rheumatism licks the joints but bites the heart” still characterizes the significance of cardiac and joint involvement as “major” manifestations, which are related to their importance as diagnostic criteria, but do not necessarily refer to their importance in the severity of the process, its activity, or prognosis.

Although the aetiological agents responsible for the initiation of rheumatoid arthritis in the human are not known, the possibility that the disease is of bacterial origin has been considered. The bacterial factors involved may be small fragments of undegraded wall components which persist for long periods within macrophages and trigger the active release of lysosomal enzymes which cause tissue destruction. The failure to identify such wall components in diseases tissues may be due to the lack of adequate sensitive techniques to detect minute amounts of these wall components, shown to trigger chronic destructive arthritis in laboratory animals. Two models of arthritis caused by mycobacterial and streptococcal wall components are described and the possible role played by immune responses, to the persisting bacterial factors, in the pathogenesis of human arthritis is discussed.