IDENTIFICATION OF A NEW SURFACTANT PROTEIN-A BINDING-PROTEIN AT THE CELL-MEMBRANE OF RAT TYPE-II PNEUMOCYTES

Antibodies against a type II pneumocyte component were developed by an auto-anti-idiotypic approach using surfactant-associated protein A (SP-A) as the immunogen. The antibodies recognize an SP-A-binding protein (similar to 170-200 kDa under nonreducing conditions, 55 kDa under reducing conditions) on the cell membrane of rat type II pneumocytes. One of the antibodies competes with SP-A for binding to type II cells. In immunization assays in vitro, with this antibody as the antigen, anti-SP-A antibodies have been generated. The SP-A-binding cell membrane protein recognized by this auto-anti-idiotypic antibody may be involved in the interaction of extracellular SP-A with the type II pneumocyte and may play a role in the regulation of alveolar surfactant metabolism.