Inflammation of the Renal System

NORMAL GLOMERULUS (Robbins pp 931)

The glomerulus consists of a tuft of capillaries lined by fenestrated endothelium. The filtration membrane has three components: 1) fenesterated endothelium, 2) basement membrane consisting of three layers: central lamina densa, peripheral lamina rara externa + interna, 3) podocyte processes (visceral epithelium). Furthermore, the glomerulus consists of mesangial cells in between the tuft of capillaries, and the parietal epithelium. The Bowman’s space is where the filtrate is formed. Note: Proteins should not pass the filtration membrane, hence is a diagnostic tool.

PATHOGENESIS OF GLOMERULAR INJURY (Robbins pp 943)

Antibody Mediated Injury:

There are two mechanisms:

• IN SITU IMMUNE COMPLEX DEPOSITION:
• 1) anti-GBM nephritis: antibodies are made against GBM components,
  
• 2) Heymann nephritis: antibodies made against the Heymann antigen also bind to visceral epithelial antigen,
  
• 3) planted antigens: antibodies made “planted antigens” that localise in kidney (i.e.: bacterial products, IgA etc).
• CIRCULATING IMMUNE COMPLEX DEPOSITION: immune complexes are formed, totally unrelated to the glomerulus but get caught up here.

• Cell mediated injury: There is evidence now that sensitized T cells cause injury.
• Activation of alternate complement pathway
• Endothelial damage
• Ischaemic injury to the glomerulus

Category: Pathology Notes