Distributions of type IV collagen α chains in the basement membrane (BM) of human skin and its appendages were analyzed by immunofluorescent microscopy using chain-specific monoclonal antibodies. The basement membrane beneath the epidermis contained [α1(IV)]2 α2(IV) and [α5(IV)]2 α6(IV) but no α3(IV) α4(IV) α5(IV); this held true for at the eccrine sweat glands and glandular ducts, sebaceous glands, hair follicles, and arrector muscles of hair. The secretary portion of the eccrine sweat glands was rich in [α1(IV)] 2 α2(IV) and had less [α5(IV)]2 α6(IV), while [α5(IV)]2 α6(IV) was abundant in the ductal portion. In the subepidermal zone, α5(IV)/ α6(IV) chain negative spots (1.9-15.0 μm) were frequently observed. Triple staining samples (Mel.2, α2(IV) and α5(IV) chains) showed that about 50% of epidermal melanocytes colocalized with such spots. Results suggest that these α5(IV)/ α6(IV) chain negative spots of the subepidermal basement membrane have a particular relationship with melanocytes and are sites for certain interactions between the two.
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