Increase in Specific Bactericidal Antibodies after Administration of Endotoxin

Abstract

MANY non-specific immune phenomena have been described in which animals became resistant to experimental infection following administration of antigeni-cally unrelated materials. None has attracted more interest than the temporary state of enhanced resistance to infection with Gram-negative bacteria which develops in mice within hours after administration of antigenically unrelated bacterial endotoxins¹. Among the many effects of endotoxins on the host is increased activity of the reticulo-endothelial system as shown by carbon clearance² and by removal of phosphorus-32 labelled endotoxin³ or bacteria⁴. In addition, changes in the serum of endotoxin-treated animals have been reported, notably increased levels of properdin⁵, bactericidins⁶ and opsonins^7,8. Passive transfer of opsonic capacity has also been demonstrated⁴. It is evident that these alterations in the host, individually or collectively, may contribute significantly to survival. Special emphasis has been placed on the nonspecific nature of the humoral factors involved, because there has been abundant confirmation of activity against bacterial strains antigenically unrelated to the endotoxin used for stimulation. Cross-reacting antibodies⁹ or a common antigen associated with the lipid complex of endotoxins¹⁰ have therefore been suggested to account for these observations.