[Inflammatory cell infiltration around beta 2-microglobulin amyloid deposition: histologic comparison of beta 2-microglobulin amyloidosis with AA or AL amyloidosis].

Thirty-one autopsy cases of beta 2-microglobulin (beta 2M) amyloidosis were pathologically investigated in comparison with 17 autopsy cases of AA or AL amyloidosis. In 20 cases (65%, 20/31) of beta 2M amyloidosis, inflammatory cells, mainly macrophages were seen infiltrating around beta 2M amyloid in intervertebral disks. The more beta 2M amyloidosis advances, the more macrophage infiltration tends to be prominent. In cases of severe beta 2M amyloidosis, the cytoplasm of macrophages around amyloid deposition were swollen with engulfed amyloid substance and were often transforming to foreign body multinucleated giant cells. In addition, granulation tissue was formed with infiltrating macrophages, foreign body multinucleated giant cells, capillary proliferation and fibrosis around beta 2M amyloid deposition. On the other hand, inflammatory cell infiltration around amyloid deposition was scarcely seen in AA or AL amyloidosis. Ultrastructurally, macrophages were abundant in phagocytic vacuoles containing amyloid fibrils. These macrophages were immunohistochemically positive for CD68, IL-1 beta and TNF-alpha. Thus, macrophage infiltration around beta 2M amyloid is thought to be responsible for local pain and tissue destruction of dialysis patients.