Luminal surfaces of fetal rat alveolar type II and Clara lung cells react with antibody to Heymann nephritis antigen

We have used affinity purified antibody, which reacts with the renal antigen gp600, to examine the immunoreactivity of pulmonary cells in the quick frozen lung tissue of fetal rats. On immunoelectron microscopy, we found that the reaction was specifically localized to the luminal surfaces of Clara cell and, as previously reported, to alveolar type II cell (ATII) membranes. No immunoreaction was seen on or in type I cells, endothelial cells or any other lung or blood cell. These studies suggest that the anti-gp600 immunoselection can be used as a marker to identify and quantify Clara and ATII cells in rat lung tissue.