ICAM-1 and integrin expression on isolated human alveolar type II pneumocytes

Adhesion molecules are involved in the recruitment of leucocytes to sites of inflammation. In this study, we determined the expression of several adhesion molecules on isolated human alveolar type II pneumonocytes. Type II pneumocytes were isolated from 10 normal lung specimens, by enzymatic digestion with dispase, followed by metrizamide gradient centrifugation and panning on immunoglobulin G (IgG)-coated plastic dishes. With the freshly isolated type II cells, immunostaining was performed using a sensitive immunoperoxidase slide technique. In all cases, 60-90% of type II cells were positive for intercellular adhesion molecule-1 (ICAM-1) (CD54). A minor portion of type II cells expressed the alpha 4 (CD49d) subunit of the beta 1-integrins, and the alpha-v (CD51) subunit of the vitronectin receptor. CD11a, CD11b, CD11c, CD18, CD49b, and CD49f failed to demonstrate any immunostaining with type II cells. In conclusion, the observation of the expression of ICAM-1 and, to a lesser degree, of some integrin subunits, may indicate that alveolar type II cells participate in local immune and inflammatory responses.