[Analysis of immunoglobulin G subclasses in chronic respiratory tract infections]

To analyze the immunological aspects of chronic respiratory tract infections, immunoglobulin G (IgG) subclass patterns were investigated in 20 patients with diffuse panbronchiolitis (DPB) and 20 patients with cystic bronchiectasis (CBE). All IgG subclasses were increased in both diseases in comparison to the normal group. Increased levels of IgG1 and IgG2 were recognized more dominantly in DPB, whereas IgG4 level was elevated in CBE. Furthermore, analysis of the ratio of IgG subclass to total IgG showed increase of IgG1 and decrease of IgG2 in both diseases, and increase of IgG4 only in CBE. On the other hand, the increase of IgG1 correlated with infection by P. aeruginosa while increase of IgG4 was recognized in the group of non-P. aeruginosa infections. These results indicate that increased IgG1 and IgG2 levels are common characteristic phenomena in chronic respiratory tract infections such as DPB and CBE, reflecting the pathophysiological aspects based on respiratory tract defense mechanisms against microorganisms, and demonstrated that differences of IgG subclass patterns are observed among DPB and CBE, and also according to causative agents.