Lying directly adjacent to the afferent and efferent arterioles and adjacent to some extraglomerular mesangial cells at the  FOLDER 20.2 Clinical Correlation: Antiglomerular Basement Membrane Antibody-Induced Glomerulonephritis; Goodpasture Syndrome
As discussed earlier in the section on the basal lamina assembly (see Chapter 5, page 139), the major building block of any basement membrane, including glomerular basement membrane (GBM), is the type IV collagen molecule. Its core structure is composed of three -chain monomers, each representing one or more of six types of -chains known for type IV collagen (see Table 6.2; page 165). Each molecule has three domains: an amino-terminus 7S domain, a middle collagenous helical domain, and a carboxy-terminus noncallagenous NC1 domain. Molecular architecture of type IV collagen is a key to understanding pathophysiology of glomerular kidney diseases. For instance, an autoimmune response to the noncollagenous NC1 domain of the 3-chain of type IV collagen [3(IV)] in the GBM is responsible for the development of anti-GBM antibody-induced glomerulonephritis. This condition is characterized by a linear deposition of immunoglobulin G (IgG) antibodies in the GBM. In some individuals, anti-GBM antibodies may cross-react with alveolar basement membrane in the lungs, producing Goodpasture syndrome.
The clinical feature of Goodpasture syndrome is rapidly progressive glomerulonephritis (inflammation in the glomeruli) and pulmonary hemorrhage due to disruption of the air–blood barrier. In response to deposition of IgG in the glomerulus, the complement system is activated and circulating leukocytes elaborate a variety of proteases, leading to disruption of the GBM and deposition of fibrin. Fibrin, in turn, stimulates the proliferation of parietal cells lining Bowman’s capsule and cause influx of monocytes from the circulation. The product of these reactions is often seen within the glomerulus as a crescent, a characteristic microscopic feature of glomerulonephritis (Fig. F20.2.1). Most patients affected by Goodpasture syndrome have a severe crescentic glomerulonephritis with transiently elevated levels of circulating anti-GBM antibodies. Formation of anti-GBM antibodies is most likely triggered by viruses, cancers, pharmacologic agents, and chemical compounds found in a variety of paints, solvents, and dyes.
Individuals with Goodpasture syndrome present with both respiratory and urinary symptoms. These include shortness of breath, cough, and bloody sputum, as well as hematuria (blood in urine), proteinuria (proteins in the urine), and other symptoms of progressing kidney failure.
The main therapeutic goal in treating Goodpasture syndrome is to remove the circulating pathogenic antibodies from the blood. This is achieved by plasmapheresis, in which blood plasma is removed from the circulation and replaced by fluid, protein, or donated plasma. In addition, treatment with immunosuppressive drugs and corticosteroids is beneficial to keep the immune system from producing pathogenic autoantibodies.