Louis H. Muschel

The sensitivity of smooth and rough Gram-negative bacteria to the immune bactericidal reaction.

Summary Rough strains of gram-negative bacteria are not necessarily more sensitive than smooth strains to the bactericidal action of normal serum or C. The resistance of certain smooth strains to C may merely reflect a lack of normal antibody in serum. Other smooth organisms may be refractory to C even when sensitized with homologous antiserum. In such instances, it is believed that the C-sensitive substance may be too far removed or inaccessible to the C enzymes activated by antigen–antibody complexes on the cell surface (6).

ACTIVITY OF THE ANTIBODY-COMPLEMENT SYSTEM AND LYSOZYME AGAINST ROUGH GRAM NEGATIVE ORGANISMS.

Discussion and summary The experimental results have confirmed previous observations that lysozyme, generally without effect itself in the killing or lysing of gram negative bacteria, enhances the bactericidal action of the antibody-complement system against these organisms(10). Both so-called normal and immune systems were affected. In addition, previous observations have indicated that cells killed by the antibody-complement system may be lysed or, in stabilizing media, converted to spheroplasts by lysozyme(2). The extreme susceptibility of rough variants to the bactericidal and bacteriolytic action of normal sera has led naturally to the postulate that specific substances or antibody may not be required for such action. The activity of precolostral calf and of newborn piglet sera against these organisms has provided some experimental basis for this concept, but further analysis of these situations is required. Partial loss of the bacteriolytic activity of normal serum against a rough organism by absorption with the cells of the homologous organism may be restored by addition of egg white lysozyme. This finding provided a basis for the concept that complement may act independently of antibody in the bactericidal reaction(5). Experiments forming the basis of this report were performed then to consider possible alternative explanations. The first of these involving the neutralization by lysozyme of the anticomplementary activity of endotoxin or other bacterial products proved untenable. The second possibility, that small amounts of normal antibody remaining in the absorbed serum were required for enhancement of activity by lysozyme, was compatible with the observed results. Addition of lysozyme to partially absorbed serum, which retained some degree of bactericidal activity, elicited a marked increase of that activity. In contrast, more completely absorbed serum was incapable of bactericidal activity with addition of lysozyme. Portions of such absorbed serum, however, served as an excellent source of bactericidal complement. Although practically inactive itself, it was highly bactericidal in conjunction with diluted immune serum (Table IV). Finally, an easily demonstrable rise in bactericidal antibody activity, as a result of immunization, may be observed with rough organisms (Table I) as with less sensitive smooth organisms(9). In conclusion, the results obtained are compatible with the classical concept that the action of complement and lysozyme in killing and lysing gram negative bacteria, both rough and smooth, requires the mediation of antibody. In addition, lysozyme may augment the bactericidal action of complement on bacteria sensitized by antibody.

ANTICOMPLEMENTARY ACTION OF ENDOTOXIN.

Summary These results have indicated that the anticomplementary action of endo-toxin upon normal serum is not mediated by an Ag (endotoxin)-Ab complex. Removal of Ab from normal serum had no detectable effect upon such anticomplementary action. In addition, the serum of the newborn piglet obtained prior to feeding and relatively lacking in Ab was more susceptible to endo-toxins anticomplementary action than the serum of its sow. Other ancillary evidence such as the marked difference in the susceptibility of the C′ of different species to endo-toxin also supports a non-immunological mechanism for its anticomplementary action. Although an Ag (endotoxin)-Ab complex may possess potent C′fixing action, other mechanisms, unknown at present, are responsible probably for the anticomplementary action of endotoxin in normal serum.

A Humoral Antibody Associated with Endotoxin Resistance.

Summary Rabbits, subjected to a series of injections with cells or purified lipopolysaccharide of one organism designed to render them endotoxin resistant, produced elevated levels of complement-fixation antibodies against otherwise serologically unrelated endotoxins. The apparent non-specificity of the response, its temporal appearance, and recall suggested the possibility that these antibodies may be related to a humoral factor involved in endotoxin tolerance.

Coliphage T2 neutralization by 7S antibody and C1

Abstract Neutralization of bacteriophage T2 by 19S and 7S fractions or rabbit antisera was studied in the presence and absence of isolated human C1. Neutralization by 19S antibody is not effected by addition of C1. Neutralization of the phage by 7S antibody, however, is markedly increased by addition of C1. Ammonia treatment of both the 7S antibody and the C1 preparations to inactive C4 did not reduce the ability of C1 to enhance neutralization. Heat treatment of C1 at 56°C for 30 min, however, did inactivate the enhancing factor as did treatment with EDTA. When added individually in the presence of antibody, the other isolated C components (C4, 2, 3, 5, 6, 7, 8, 9) were ineffective in the neutralization of T2.