We have previously reported that connective tissue cells in the superficial dermis preferentially express α1(XVI) collagen rather than those in the lower dermis. Double immunofluorescence labeling using the antibodies for α1(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 α1(XVI) collagen as well as factor XIIIa. The physiologic significance of colocalization of α1(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 α1(XVI) polypeptide was found. Incubation of recombinant NC11 of α1(XVI) polypeptide with factor XIIIa in vitro produced a covalent cross-linking complex on sodium dodecylsulfate-polyacrylamide gel electrophoresis. The results indicate that α1(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.
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