[Study on the role of mucoid strain in chronic airway infections]

This study was investigated to eludiate the clinical role of immune complexes (IC) formed by alginate of persistently colonized mucoid strain in chronic airway infection. 1. Clinical Observation Twenty-four cases colonized with mucoid strain and 16 cases with non-mucoid strain were enrolled. Their serum indexes to anti-alginate specific IgG subclass antibodies and level of IC were determined by enzyme linked immunosorbent assays. Significantly higher level of the IgG1, IgG3 and higher level of IC were observed in the group of mucoid positive cases. Deposition of IgG1, IgG3, and IC on the affected part of interstitial lung tissue in a case of persistent infection with mucoid Pseudomonas aeruginosa was detected. 2. Experimental Observation Ninety mice immunized with alginate were used. They were intubated with 20 micrograms/body of alginate, 4 x 10(6) colony forming unit/body of mucoid Pseudomonas aeruginosa: PT1252, or 40 microliters/body of IC into each group. Then after Fc gamma receptor (Fc gamma R) on neutrophils in bronchoalveolar lavage fluid was analyzed by flow cytometric technique. Expression of Fc gamma R on neutrophils was inhibited against alginate intubation and IC one. In contrast, Fc gamma R expression was increased at initial phase after mucoid Pseudomonas aeruginosa intubation, which was influenced by nonspecific activation of neutrophils due to bacterial infection. 3. Conclusive Words From the above, The expression of Fc gamma R on neutrophils was inhibited by alginate. It may be that IC deposition on lung tissue in chronic airway infection with mucoid strain was persisted by poor binding ability of neutrophils to IC, in spite of a large numbers of neutrophils accumulation. Consequently, the immune-reaction induced by alginate makes clinical prognosis of such patients more intractable.