THE EFFECTS OF SYSTEMIC IMMUNIZATION ON PULMONARY CLEARANCE OF PSEUDOMONAS-AERUGINOSA

Abstract

Systemic immunization with gram-negative organisms enhances the subsequent pulmonary clearance of these organisms. The early time course of this phenomenon was studied and related it to the time of appearance of polymorphonuclear leukocytes (PMN) and anti-Pseudomonas antibody in bronchoalveolar lavage (BAL). Mice were immunized i.p. twice, separated by 1 wk, with 105 formalin-treated Pseudomonas aeruginosa. Two weeks later, they received an intrabronchial inoculum of 2.9 .times. 106 or 4.6 .times. 107 Pseudomonas organisms. Two, 4 and 6 h later, clearance and total PMN and anti-Pseudomonas antibody in the BAL were assessed. Clearance was enhanced in immunized mice at the lower inoculum. At the higher inoculum, bacteria were growing in lungs of both groups, although they were inhibited in immunized mice. Total PMN in the BAL increased progressively in both groups of mice, but net recruitment was diminished with the high inoculum. There were significant differences in the PMN in the BAL between control and immunized mice with high inoculum. Anti-Pseudomonas IgG 1st appeared in the BAL at 2 h, anti-Pseudomonas IgM at 6 h. Anti-Pseudomonas IgG is an effective early pulmonary opsonin. With high inoculums, immunization may aid pulmonary defenses by diminishing the magnitude of the decrement of PMN in the lung.