Nichols: Glomerular Structure and Mech of Disease Flashcards
What part of the glomerulus is significantly thicker in men than women?
GBM (glomerular basement membrane)
Anti-GBM disease is significantly more common in what population?
Young, white males
What happens to the glomeruli in nephrotic syndrome?
Podocytes retract foot processes, leading to loss of slit pore diaphragms, so that long segments of capillary are invested by cytoplasm of a single podocyte. Foot processes detach from the basement membrane, which degrades and allows proteins to leak into urinary space.
Name the laminae of the GBM
1) lamina lucida/rara interna (closer to endothelium) 2) lamina densa 3) lamina rara externa (closer to epithelial cells)
What is the space between to pediceles called?
filtration slit
What is the thin structure bridging the space between two pediceles
slit pore diaphragm
What proteins are found in the slit pore diaphragm, and what are their functions?
1) cadherin and FAT bind adjacent pediceles 2) nephrin and podocin play a role in filtration
Mutations in which slit pore diaphragm proteins result in congenital nephrotic syndrome?
nephrin and podocin
What are the main components of basement membrane? Which one is the major component of GBM?
1) perlecan 2) entactin 3) laminin 4) fibronectin 5) type IV collagen - major component of GBM
Which component of basement membranes imparts the strongest negative charge, and why is this important?
Perlecan (highly charged PG containing heparan sulfate) - important for keeping albumin from entering and traversing the basement membrane
How many alpha chains form one collagen molecule?
3 alpha chains form a collagen molecule.
What is the non-helical, globular domain of a collagen molecule called? Why is this domain important?
Non-collagenous (NC) domain. Some diseases, such as Goodpasture syndrome, are caused by antibodies directed against an epitope in the NC1 domain of the alpha3 chain
What are mesangial cells?
Mesenchymal cells with phagocytic and contractile properties, equivalent to pericytes around other capillaries. Substances trapped in GBM flow along GBM until they get to mesangial matrix, where they are phagocytosed
What are the three common mechanisms of glomerular disease? Which is the most common?
1) Immune-mediated 2) Metabolic (diabetic) 3) Hemodynamic (hypertensive) - most common
What are the mechanisms in which immune-mediated glomerular disease can occur?
1) Immune complexes can be deposited from circulation OR formed in situ 2) In situ antibodies can be against intrinsic (fixed) antigens OR planted antigens, originally from bloodstream
What is the mechanism of glomerular damage in lupus nephritis?
Large circulating immune complexes cannot pass through GBM and get stuck in subendothelial location, causing the formation of “wire loops”
What is the mechanism of glomerular damage in Goodpasture syndrome?
Circulating antibodies against GBM deposit in a subendothelial location, in a linear pattern along GBM
What is the mechanism of disease in membranous glomerulonephritis?
Circulating antibodies against antigens in the cell membrane of podocytes deposit outside of basement membrane and form in situ immune complexes, injuring podocytes.
What kind of pattern do immune complexes have on immunofluorescence?
granular