DIFFERENTIAL EXPRESSION OF LAMININ POLYPEPTIDES IN DEVELOPING AND ADULT HUMAN KIDNEY

We studied the expression of laminin chains in embryonic and adult hum an kidney by indirect immunofluorescence with monoclonal antibodies (M Abs), In embryonic human kidney, immunoreactivity for laminin alpha 1, beta 1, and gamma 1 chains was found in basement membranes (BMs) of p rimary vesicles, in comma- and S-shaped bodies, and in more mature sta ges of glomeruli and in tubules, The beta 2 chain of laminin was absen t in the early glomerular structures but was prominent in BMs of matur ing glomeruli (GBMs) and Bowman's capsule (BCBMs) and was also detecta ble in some tubules, Both the beta 2 and alpha 2 chains were variably seen in medullary tubule BMs, In adult human kidney, laminin alpha 1 c hain was seen in GBMs and all tubule BMs (TBMs) as well as in arterial smooth muscle BMs (SMBMs). Laminin beta 1 chain reactivity was found in all TBMs, but not in GBMs or SMBMs, In the glomerulus, a distinct m esangial type of reaction was revealed with the MAbs to beta 1 and alp ha 2 chains. The GBMs and SMBMs reacted with MAbs to the beta 2 chain, but reactivity was lacking in BCBMs, Laminin gamma 1 chain immunoreac tivity was weakly present in BCBMs, GBMs, and SMBMs, The alpha 3 and b eta 3 chains could not be detected in developing or adult human nephro n, The results show that during development the BMs in human nephron u ndergo distinct changes, laminin beta 1 chain being transiently co-exp ressed with alpha 1 chain during early glomerular development and then becoming replaced by the beta 2 chain, which, on the other hand, disa ppears from the BCBMs on maturation. The alpha 2 chain appears to emer ge in the mesangium late during development.