Objective: To explore inflammatory infiltration and its effects on the formation of abdominal aortic aneurysm (AAA).
Methods: Immunohistochemical technique was used to detect lymphocyte (CD45 positive) and macrophage (CD68 positive) infiltration while in situ hybridization was applied to investigate the mRNA expression of Matrix Metalloproteinase-9 (MMP-9) in 20 cases of human AAA and 4 cases of normal human abdominal aortas.
Results: Inflammatory infiltration occurred in every case of AAA with various degree, and there was a parallel tendency between the degree of injury of abdominal aortic elastin and that of inflammatory infiltration in AAA. Inflammatory infiltration was not found in normal aortas. MMP-9 mRNA was detected in macrophages and lymphocytes in all 20 cases, in smooth muscle cells in 13, and not in normal abdominal aortas.
Conclusions: Inflammatory infiltration attended and enhanced the formation of AAA through a complex of sequence of biochemical, cellular and immune events.