Type XVI collagen is expressed in factor XIIIa+ monocyte-derived dermal dendrocytes and constitutes a potential substrate for factor XIIIa.

We have previously reported that connective tissue cells in the superficial dermis preferentially express alpha1(XVI) collagen rather than those in the lower dermis. Double immunofluorescence labeling using the antibodies for alpha1(XVI) collagen and factor XIIIa (plasma transglutaminase), which is a marker of dermal dendrocytes, demonstrated that both antibodies reacted with the same cells in the superficial dermis of normal skin as well as the lesional skins of dermal dendrocyte-related disorders, dermatofibroma, and psoriasis. Dermal dendrocytes are considered to be established by a culture of peripheral blood monocytes in the presence of granulocyte macrophage-colony stimulating factor and interleukin-4. Reverse transcription--polymerase chain reaction, metabolic labeling, and immunofluorescence studies demonstrated that treatment of CD14+ peripheral blood monocytes with granulocyte macrophage-colony stimulating factor/interleukin-4 over a period of 8 d resulted in the induction of alpha1(XVI) collagen as well as factor XIIIa. The physiologic significance of colocalization of alpha1(XVI) collagen and factor XIIIa in the tissue and their coordinate induction in CD14+ monocyte-derived dendritic cells in vitro was studied. Considerable incorporation of [3H]putrescine by factor XIIIa into recombinant noncollagenous domain (NC) 11 but not into collagenous domain (COL) 1.NC1 domain of the alpha1(XVI) polypeptide was found. Incubation of recombinant NC11 of alpha1(XVI) polypeptide with factor XIIIa in vitro produced a covalent cross-linking complex on sodium dodecylsulfate-polyacrylamide gel electrophoresis. The results indicate that alpha1(XVI) collagen is constitutively expressed by most dermal dendrocytes in the skin and dendritic cells differentiated from peripheral blood monocytes in vitro. Type XVI collagen is expressed in factor XIIIa+ dermal dendrocytes and may form an intermolecular cross-linking through NC11 domain by the reaction catalyzed by factor XIIIa contributing to the structural integrity of factor XIIIa+ dendritic cell-rich tissues.

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.

Linear hyperpigmentation with extensive epidermal apoptosis: a variant of linear lichen planus pigmentosus?

We report 3 female patients who rapidly developed pigmented patches in a linear arrangement. Histologically there was minimum epidermal basal cell damage and bandlike lymphocyte infiltration in the dermis, but focal massive apoptotic materials positively stained with antikeratin antibody were prominently seen in the papillary and subpapillary dermis. We considered these cases as a variant of linear lichen planus pigmentosus with unique histologic change of severe epidermal apoptosis. These histologic features may represent a severe apoptotic change in the end stage of lichenoid tissue reaction.

Coexistence of pseudoxanthoma elasticum-like papillary dermal elastolysis and linear focal dermal elastosis.

An 89-year-old Japanese woman had pseudoxanthoma elasticum-like papillary dermal elastolysis on the neck and linear focal elastosis on the flexor aspects of the legs and thighs. The lesions of both diseases had similar histologic patterns-loss of elastic fibers in the papillary dermis and accumulation of normal-appearing elastic fibers in the subpapillary or mid dermis. Immunohistochemical analysis showed elastin, and microfibril-associated proteins (fibrillin 1 and 2 and microfibril associated glycoprotein 1 and 4) were absent or decreased in the papillary dermis and present in the accumulated elastic fibers in both lesions. The association of 2 diseases on different areas of the same patient and histologic and immunohistologic similarities between the diseases suggest that, despite the clinical differences, both diseases are closely related.