Expression of 67‐kDa elastin receptor in annular elastolytic giant cell granuloma: elastin peptides induce monocyte‐derived dendritic cells or macrophages to form granuloma in vitro

Annular elastolytic giant cell granuloma (AEGCG) is characterized by non‐palisading granuloma and elastophagocytic giant cells. Granulomas consist of structured masses of macrophages, dendritic cells, and T lymphocytes which play an essential role in granuloma formation. Two lineage systems of dendritic cells and macrophages originated from peripheral blood monocytes have been established in vitro . To know how elastin fragments are involved in the granuloma formation in AEGCG, we tested in vitro whether elastin fragments potentially induce monocyte‐derived macrophages or dendritic cells to form granuloma and multinucleated giant cells. Immunohistochemical studies of the lesional skins of AEGCG ( n  = 5) revealed that the 67‐kDa elastin receptor was specifically expressed in the epithelioid or multinucleated giant cells. Proliferation of factor XIIIa + cells and CD68 + cells was also seen in the lesional skins of AEGCG. Factor XIIIa + dendritic cells or CD68 + macrophages were established by the treatment of granulocyte/macrophage‐colony stimulating factor (GM‐CSF)/interleukin‐4 or M‐CSF, respectively. Further treatments of these dendritic cells or macrophages with elastin peptide resulted in the formation of granuloma or multinucleated giant cells which were immunoreactive with anti‐67‐kDa elastin receptor antibody. These findings suggest that elastic tissue induces factor XIIIa + cells and CD68 + macrophages to form granuloma or multinucleated giant cells and plays an essential role in the formation of granuloma in AEGCG.