Identification of a renal proximal tubular epithelial antigen coexpressed on leukocytes

Renal tubular epithelial cells (TEC) and leukocytes express distinct cell adhesion molecules and integrins in common. To identify additional proximal TEC molecules that are coexpressed on leukocytes, we have generated a panel of monoclonal antibodies (mAb) by immunization of rats with a mouse T cell line. One of these mAb (I-72) recognizes a 210-kD antigen on cultured TEC. The staining pattern in several cell lines allowed exclusion of known TEC surface molecules as being the antigens recognized by the I-72 mAb. Immunofluorescence staining of mouse kidney with the I-72 mAb demonstrated prominent expression on the apical but not the basolateral side of proximal tubules, predominantly in the S1 segment. I-72 was also expressed in the loop of Henle, the collecting duct, and on endothelial cells of intrarenal vessels. We have thus generated a mAb which identifies an unusual renal proximal tubular brush border molecule that is coexpressed on T cells. Molecular structure and the function of I-72 need to be defined in further studies.