TYPE-IV COLLAGEN ALPHA-5 CHAIN - NORMAL-DISTRIBUTION AND ABNORMALITIES IN X-LINKED ALPORT SYNDROME REVEALED BY MONOCLONAL-ANTIBODY

Although the evidence indicates that mutation of the gene for the alph a 5 chain of type IV collagen, alpha 5-(IV), is the primary, defect in X-linked Alport syndrome, protein data for the alpha 5(IV) chain zuit h regard to its normal distribution and its distribution in patients w ith Alport syndrome is lacking. We produced a rat monoclonal antibody (H51) by immunizing mts with a synthetic peptide corresponding to the nonconsensus amino acid sequence of alpha 5(IV) NCI domain H51 reacted by Western blotting with 26-kd cationic monomers and associated dimer s of human type IV collagen NC1 domain. Immunohistochemical studies de monstrated that in normal human kidney alpha 5(IV) was present in the glomerular basement membrane and basement membranes of the Bowman's ca psule and in some tubules (collecting ducts). The alpha 5(IV) chain wa s also detected in the basement membranes of normal skin, eye, and lun g. Male patients with X-linked Alport syndrome revealed no reactivity of renal and epidermal basement membranes with H51, whereas alpha 5(IV ) staining was normal in the glomerular basement membrane of patients with other types of glomerular diseases, including benign familial hem aturia. The staining was also normal in the skin of nonaffected males in X-linked Alport families. Female heterozygous for Alport syndrome e xhibited a discontinuous or mosaic pattern in the immunofluorescent st aining of the epidermal basement membrane. These findings confirm that in patients with X-linked Alport syndrome there are abnormalities in alpha 5(IV) in renal and epidermal basement membranes at the protein l evel. Immunofluorescent staining of skin biopsies with this antibody m ay be of value in making a diagnosis of Alport syndrome, and, furtherm ore, may aid in detecting carrier females in whom urinary abnormalitie s are often mild or silent.