Characterization of a monoclonal antibody recognizing the blastemal element of Wilms' tumors and fetal kidneys.

A blastema-associated antigen (BLA-1) was detected using a monoclonal antibody against malignant blastema from a Wilms' tumor. The localization of BLA-1 was investigated in a series of nine Wilms' cases, five fetal, one childhood, and two adult kidneys. In this series, BLA-1 antibody consistently stained cell surfaces of all Wilms' tumors containing blastemal components. The same staining pattern was maintained in tumors grown as heterotransplants in nude mice. The expression of BLA-1 antigen was examined in normal blastema of fetal kidneys. BLA-1 was immunolocalized to condensed blastemal cells in the nephrogenic zone throughout gestation. In addition, kidney samples from a young child or adults contained no blastemal cells and therefore showed no blastemal cell surface staining. Glomerular mesangial cell staining was demonstrated in kidneys from 12 weeks of gestation through adulthood. This staining in developing and mature glomeruli implies that mesangial cells may be derived from condensed blastemal cells. The finding of a cell surface antigen common to Wilms' blastema, fetal blastema, and mesangial cells has not been previously demonstrated.