Activated a and m memory a alveolar T T-lymphocytes iin iidiopathic eosinophilic p pneumonia

ABSTRACT: To investigate the possible involvement of T-lymphocytes in theimmunopathogenesis of idiopathic eosinophilic pneumonia (IEP), we have evalu-ated the phenotypic characteristics both of peripheral blood and alveolar lympho-cytes in six patients with symptomatic IEP, and in 24 healthy nonsmokers as controls,by employing bronchoalveolar lavage (BAL), monoclonal antibodies, and flow-cytometry.In IEP, total and differential cell counts showed a mild alveolitis with an increaseof eosinophil percentage and number; the alveolar lymphocyte count was alsoincreased. In BAL, the total number both of CD4+ and CD8+ lymphocytes wassignificantly raised; CD4+ cells expressed early (CD25) activation antigens. Theanalysis of CD45R0, CD45RA and CD62L coexpression in IEP patients, when com-pared to healthy controls, revealed an accumulation of alveolar CD4+ cells show-ing phenotypic repertoire usually expressed by memory T-cells (CD45R0+, CD45RA-,CD62L-). CD8+ alveolar lymphocytes did not show any significant increase of acti-vation antigen coexpression. Circulating lymphocytes were not significantly increasedand showed only a significantly higher CD25 expression.These data suggest that a pivotal role is played by activated and memory CD4+alveolar lymphocytes in IEP patients.