CD44 STANDARD AND VARIANT ISOFORM EXPRESSION IN NORMAL HUMAN SKIN APPENDAGES AND EPIDERMIS

CD44 isoforms have been implicated in tumor progression and metastasis formation. This study presents a thorough immunohistochemical analysi s of CD44 standard and isoform expression in normal human skin appenda ges and epidermis applying monoclonal antibodies against CD44s, CD44v3 , -v4, -v5, -v6, and -v9. An improved immunohistochemical protocol wit h microwave-based antigen retrieval in paraffin sections and heavy met al amplification of the diaminobenzidine reaction product provided enh anced resolution and sensitivity as compared to studies on frozen sect ions. The hair follicle, the seborrheic and eccrine sweat glands were strongly positive for all CD44 isoforms studied. In the latter, the cl ear cells but not the dark (intercalated) cells were positive. The sud oriferous ducts adjacent to the glands were weakly positive for all CD 44 isoforms and strongly positive near the skin surface. In the apocri ne glands, the basal cells showed only a moderate positivity. The myoe pithelial cells expressed only CD44s. In the epidermis, all CD44 isofo rms were detectable, with strongest CD44 immunostaining in the lower t hird of the stratum spinosum and weaker staining in the stratum basale and the upper two-thirds of the stratum granulosum. The stratum granu losum and corneum were unreactive. Thus, a regional and cell type-spec ific CD44 expression was revealed.