Combination therapy of anti-endotoxin antibody and gentamicin in the immunosuppressed mice with Pseudomonas aeruginosa infection.

Therapeutic effect of anti-endotoxin antibody in combination with or without an antibiotic, gentamicin, was studied in DD-strain mice experimentally infected with Pseudomonas aeruginosa. Mice were treated by various immunosuppressive agents such as 60Co irradiation, cyclophosphamide, azathioprine or cortisone acetate prior to infection. Anti-endotoxin antibody was made in mice by immunization with original endotoxin protein (OEP). F(ab')2 fragment of IgG prepared from pooled immune sera was administered intravenously without side effects. Large dose of the antibody resulted in remarkable therapeutic effect even in absence of the antibiotic. Small dose of the antibody enhanced the therapeutic effect of gentamicin. Differential effect of the immunosuppressants for T and B lymphocyte populations was examined by anti-theta cytotoxicity test. Resistance of DD-strain mice to P. aeruginosa infection was not related to these lymphocyte population changes.