The contemporary concept of alveolitis

The concept of alveolitis as an exudative reaction dominated by plasma and cell accumulation within alveolar air spaces is reappraised in the light of new data concerning the reactional dynamics challenged by non-immune and immune agents vehiculated by air and blood ways, of the systemic approach of lung processes, of the consideration of alveolar walls and the air space delimited by them as a whole. The participation of alveolar mesenchymal cells and of blood cells and plasma in the development of alveolitis is obvious and the changes of alveolar walls are morphogenetically prevailing in time and space over those of air spaces, whose reactions represent only a secondary phase of the lung response. Both the primary parietoalveolar phase and the secondary air space phase form a whole reactional modality of the lung in which accumulative and proliferative, exudation and mobilization changes are highly interacting in the building up of alveolitis. The involved immune mechanisms may determine special cell accumulations, but the basic mechanism, the stereotype and the sequences of this reactional modality of the lung are not essentially different from the non-immune alveolar reactions.