Experimental study on the influence of alginate induced immune complex on BALF cells

Immune complex containing alginate and antialginate antibodies plays an important role in the disease-progress of chronic airway infection with mucoid-alginate producing strains. For the purpose of clarifying the immune-pathogenic influence of the alginate induced immune complex (alg-IC) on inflammatory cells in bronchoalveolar lavage fluid (BALF), an experimental study was performed. The alginate immunized mice were injected through the trachea with alg-IC extracted from the immunized mouse serum in advance, and the changes in BALF-cells, such as macrophage, neutrophil, lymphocyte, CD16/32 positive neutrophil, CD4+ lymphocyte, CD4+CD45+ lymphocyte, CD8+ lymphocyte, CD8+CD11b- lymphocyte were investigated along with the passage of time as compared with those of the non-immunized mice. 1) On the 2nd day after intratracheal injection, the time which was chosen as an acute phase, the total count of macrophages, neutrophils, lymphocytes were increased in both groups. However CD16/32 positive neutrophil (with the expression of Fc-gamma recepter on it) was significantly decreased in the immunized group. 2) On the 5th day being chosen as the resolving phase of acute inflammation, the number of the increased inflammatory cells tended to recover to the base line value in both groups. But the continuous decrease in CD16/32 positive cell and the significant increase in CD4+CD45+ lymphocytes were found in only the immunized group. 3) On the 16th day being chosen as the beginning of the chronic phase, all inflammatory cells investigated in the non-immunized group recovered to the base line level. In the immunized group, however, significantly higher values of neutrophil-count still remained, in spite of the decrease in CD 16/32 positive neutrophils. Also, CD4+CD45+, CD8+, CD8+CD11b- lymphocytes were significantly at a higher level. 4) Histological findings in the lung tissue was supported the above findings. 5) From the above, in the alginate immunized group, the scavenging function of neutrophils for the alg-IC deposited in lung tissue would be suppressed resulting from the decrease in CD16/32 positive neutrophils, in spite of the increase in total count of neutrophils. Consequently, long term deposition of alg-IC in the lung would induce an accumulation of cytotoxic CD8+ T lymphocyte or other lymphocytes as one of the cell-mediated immune responses. This indicates that such a harmful immune reaction induced by alg-IC leads the chronic infection with mucoid-alginate producing pathogens to be more intractable.