Codistribution of collagen types IV and AB2 in basement membranes and mesangium of the kidney. an immunoferritin study of ultrathin frozen sections.

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Abstract
Affinity-purified rabbit antibodies specific for collagen types I, III, AB2 and for a partially characterized type IV collagen derived from a murine tumor were used to study the distribution of collagens in the normal mouse kidney. Immunofluorescence staining of conventional frozen sections demonstrated that types I and III were present in bundles around larbe vessels and in fibers surrounding glomeruli and tubules, whereas types IV and AB2 were distributed in a linear fashion along basement menbranes of tubules, glomeruli, and Bowman''s capsule and in the mesangial stalk. The distribution of types IV and AB2 was examined at the ultrastructural level by staining of 600- to 800-.ANG. thick frozen sections with a three-stage procedure employing specific collagen antibodies, biotinyl sheep antirabbit Ig[immunoglobulin]G, and avidin-ferritin conjugates. Labeling by this procedure demonstrated codistribution of types AB2 and the putative type IV in all 3 basement membranes. Mesangial matrix contained both of these collagen types. These results support recent biochemical evidence of collagen heterogeneity in basement membranes, and also support the concept of a structural relationship between mesangial matrix and glomerular basement membranes.