Lung pathogenesis. IV. Persisting pathogens and accumulative-proliferative cellular reactions in chronic lung processes (a systemic approach).

Persistence of pathogens within lung structures is due to the co-operation of the impairment of local defence means, of the aerial concentration and of the immunopathogenic component of processes. The action of pathogens, analysed in the framework of factor assemblies determining the process sequences, induced, as the most frequent reaction, cell proliferation and accumulation with the insertion of chemotactically retained circulating cells and their homing within alveolar wall interstitia and peribronchovascular sheets. The relations between the different inserting cells and the local ones are analyzed, with emphasis upon the derepression of local mechanisms of the steady state, secondary proliferation of both local and newly inserted cells, and current evolution to fibrosis.