Activity of the Antibody-Complement System and Lysozyme Against Rough Gram Negative Organisms. ∗

Abstract

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.