Spleen - Amyloid

Amyloidosis is a systemic disease characterized by the extracellular deposition of amorphous proteinaceous material in multiple tissues, including spleen, liver, and kidney. In the spleen of mice, amyloid is deposited in the red pulp and adjacent to the white pulp (marginal zone) (Figure 1 and Figure 2, arrows). When this lesion is severe, it can result in white pulp atrophy (Figure 1, arrowhead). Amyloid can be identified by apple-green birefringence when stained with Congo red and visualized under polarized light, or it can be detected immunohistochemically. Amyloidosis is rare in B6C3F1 mice and rats. The incidence of spontaneous amyloidosis in mice increases with age and may be influenced by various factors, including breeding origin, diet, environment, and inflammation. In mice, spontaneous age-associated (senile) amyloidosis has been associated with amyloid apolipoprotein A2 (ApoA2) deposition, whereas inflammatory-induced amyloidosis has been correlated with serum amyloid A (an acute-phase protein). ApoA2 is a major constituent of serum high-density lipoprotein in mice.