ACTIVATED AND MEMORY ALVEOLAR T-LYMPHOCYTES IN IDIOPATHIC EOSINOPHILIC PNEUMONIA

To investigate the possible involvement of T-lymphocytes in the immuno pathogenesis of idiopathic eosinophilic pneumonia (IEP), we have evalu ated the phenotypic characteristics both of peripheral blood and alveo lar lymphocytes in six patients with symptomatic IEP, and in 24 health y nonsmokers as controls, by employing bronchoalveolar lavage (BAL), m onoclonal antibodies, and flow-cytometry. In IEP, total and differenti al cell counts showed a mild alveolitis with an increase of eosinophil percentage and number; the alveolar lymphocyte count was also increas ed, In BAL, the total number both of CD4+ and CD8+ lymphocytes was sig nificantly raised; CD4+ cells expressed early (CD25) activation antige ns, The analysis of CD45RO, CD45RA and CD62L coexpression in IEP patie nts, when compared to healthy controls, revealed an accumulation of al veolar CD4+ cells showing phenotypic repertoire usually expressed by m emory T-cells (CD45RO+, CD45RA-, CD62L-), CD8+ alveolar lymphocytes di d not show any significant increase of activation antigen coexpression , Circulating lymphocytes were not significantly increased and showed only a significantly higher CD25 expression. These data suggest that a pivotal role is played by activated and memory CD4+ alveolar lymphocy tes in LEP patients.