Specific passive immunity against Pseudomonas aeruginosa sepsis was assessed in granulocytopenic dogs. Dogs were infused with either normal or antipseudomonas immune plasma 24 h before pseudomonas challenge. They were challenged intravenously with 10(7) serotype 6 P. aeruginosa during granulocytopenia. Treatment was evaluated by observation of survival periods, febrile responses, type 6 pseudomonas antibody titers, and quantitative cultures of blood and tissues. The results demonstrated that passively immunized dogs did not survive infection. Both normal-plasma and immune-plasma recipients had bacteremia at death, with median values of 980 and 470 pseudomonas per ml of blood, respectively. All dogs had marked febrile responses 24 h after pseudomonas challenge and had high concentrations of pseudomonas in their lung tissue at death, with median values of 10(8) pseudomonas per g of wet tissue weight. After plasma infusion, immune-plasma recipients had high concentrations of anti-pseudomonas antibody, with total antibody titers ranging from 256 to 1,024 and a median value of 1,024. These titers were comparable to titers attained in a previous study from our laboratory using active immunization with pseudomonas lipopolysaccharide vaccine, where the median total anti-pseudomonas antibody titer was 2,048. Actively immunized animals, however, were significantly protected against pseudomonas sepsis and had prolonged survival periods and prevention of bacteremia. The present study demonstrates that circulating type-specific antibody is not solely responsible for the protection afforded to granulocytopenic dogs actively immunized against pseudomonas.
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