[Criteria for T-lymphocyte activation in alveolitis]

A lymphocytic alveolitis is a common stage in a group of interstitial pulmonary disorders, where the lymphocytes accumulating in the alveoli play a major pathogenic role by their regulatory function or through their effects on the inflammatory reaction; controlling the outcome to healing, chronicity or fibrosis. Studies on lymphocytes obtained by bronchoalveolar lavage enable different parameters to be determined whose semiological value is discussed from information acquired in in vitro models of lymphocyte activation. These models show the need for activating signals acting in a sequential manner on cells whose function and mode of response are extraordinarily diversified. Three successive phases may be defined at the time of activation: first a membrane stage consisting of changes in the lipids (metabolism of arachidonic acid) and the cytoskeleton of the cell, a second stage corresponding to the start of the "blastic transformation" with the production of lymphokines with an increase in protein and RNA content (phase G1), then a third stage of DNA synthesis (phase S-G 2) preceding cell division; it is needed for the expression of new markers of differentiation. Nowadays the joint study of the phases of the cell cycle and the expression of antigenic differentiation, identified by monoclonal antibodies within a heterogeneous population, benefit from techniques of flow cytometry. These methods, combined with a measure of mediator production (interleukines) or of non-specific markers of activation liberated by T or B lymphocytes or by macrophages ought to succeed in defining the evolutionary stages or the immune-clinical types of alveolitis. Finally these methods allow the development of cellular immunopharmacology which should lead to new treatments.