Immune stimulation of lung bactericidal activity: evidence for both cellular and humoral participation after immunization with Serratia marcescens

Effect of presensitization of Nocardia asteroides with specific antibody on the viability of the organism

Nocardia asteroides from various growth phases was treated in vitro with normal rabbit sera, immune rabbit sera containing nocardial polyclonal antibodies and a monoclonal antibody. At intervals, samples were grown in broth or on blood agar plates to determine their viability. Log and stationary phase cells were injected intra-peritoneally into female BALB/c mice and their survival rates in the liver and spleen were determined. Presensitization with antibodies reduced the viability of the log phase cells by 48% and that of the late stationary phase by 4%. The antibody-treated log phase organisms were less viable on the blood agar medium and in the spleen and liver than the control organisms. This indicates that pretreatment with antibody has a lethal effect on N. asteroides and affects its survival in vivo.

Effect of systemic immunization on pulmonary clearance of Haemophilus influenzae type b

The effect of systemic immunization on pulmonary clearance of Haemophilus influenzae type b (Hib) was studied in a mouse model system. Immunization of mice by intraperitoneal injection of viable Hib cells resulted in the appearance of Hib-directed antibodies in both serum and bronchoalveolar lavage fluid. The development of this Hib-directed antibody activity was associated with significant enhancement of early pulmonary clearance of Hib. Systemic immunization did not affect the recruitment of polymorphonuclear leukocytes to the alveoli, suggesting that the enhanced clearance of Hib observed in immunized animals was due to specific antibodies which promote either phagocytosis or extracellular killing of Hib. The spectrum of Hib-directed antibody specificities detected in sera from immunized animals was essentially identical to that detected in bronchoalveolar lavage fluids from these same animals. Similarly, intravenous administration of an immunoglobulin G monoclonal antibody specific for Hib lipopolysaccharide resulted in the subsequent appearance of this antibody in the alveolar spaces where it enhanced pulmonary clearance of Hib. This study shows that this mouse model system can be used to measure the effect of both active and passive immunization on the clearance of Hib from the lower respiratory tract.