Immunocytochemical characterization of isolated human type II pneumocytes

The expression of surface antigens on human type II pneumocytes is unknown but may be important in diagnostic cytology of bronchoalveolar lavage specimens. Thus, the immunocytochemical reactivity of isolated human type II pneumocytes was determined using a panel of commercially available monoclonal antibodies (MAbs). Type II pneumocytes were isolated from fresh human lung tissue obtained from surgical specimens (four non-smokers, six heavy smokers) after enzymatic digestion with dispase and subsequent discontinuous metrizamide gradient centrifugation. MAbs OKIa; EMA; OKT9; BMA 130a, b and c; EP4; TAG 72; HEA 125; and Leu M1 were studied using the peroxidase-antiperoxidase adhesive slide assay method. In all cases, type II pneumocytes reacted positively with OKIa, BMA 130a, BMA 130b, EMA, EP4, TAG 72 and HEA 125 and negatively with OKT9, BMA 130c and Leu M1. The percentage of positively reacting type II pneumocytes was 90 for OKIa, HEA 125 and EP4; 80 for EMA; 50 for TAG 72 and BMA 130a; and 5 for BMA 130b. Human type II pneumocytes share the expression of several antigens with epithelial tumor cells. This limits the usefulness of these markers with respect to differentiating between reactive type II pneumocytes and malignant cells.