Humoral Immunity to Type-Specific and Cross-Reactive Antigens of Gram-Negative Bacilli

Abstract

Active and passive immunization with antigens shared by most Enterobacteriaceae demonstrated that antibodies against the basal portion of core lipopolysaccharide (Re determinants) protected against challenge with heterologous, smooth gramnegative bacilli. Active immunization with Re induced a 13- to 100-fold increase in the number of Escherichia coli 107 and Klebsiella pneumoniae required for an ld₅₀. Other rough mutants and common enterobacterial antigen (CA) failed to induce consistent protection. In specimens of acute serum, antibody titers to O-specific antigen, CA, and Re were related to the frequency of shock or death in 206 episodes of gram-negative bacteremia. Frequency of shock and death could not be related to height of antibody titers to 0 antigen or CA. These complications occurred equally often in those with high and low antibody titers. In contrast, a significant correlation (P < .01) was observed between increasing titers of Re antibody and decreasing frequency of shock or death.