The epithelial layer of the skin provides an essential function as a protective barrier against insult from the outside environment. The major cell type in this layer is keratinocytes which consists around 85% of living epidermal cells. Keratinocytes are the cells of stratified squamous epithelia. It is so named because its most abundant protein is keratin. Keratinocyte divide and are thus generated in the basal layer of the epidermis; this division is followed by a programmed death as they produce keratin and move up to the surface of the epidermis. Keratinocyte proliferation, differentiation, and apoptosis are complex and carefully choreographed processes. Besides the protective function, keratinocytes also play a central role in tissue homeostasis, wound healing, cancers, and skin-based gene-therapy. Human keratinocytes express adhesion molecules and cytokines indicating their participation in skin innate immunity and homeostasis in vivo. HEK-a from AcceGen Biotech Research Laboratories are isolated from adult human epidermal tissue. HEK-a are cryopreserved on primary culture and delivered frozen. Each vial contains >5 x 10^5 cells in 1 ml volume. HEK-a are characterized by immunofluorescent method with antibodies to cytokeratine-18 and -19. HEK-a are negative for HIV-1, HBV, HCV, mycoplasma, bacteria, yeast and fungi. HEK-a are guaranteed to further expand for 15 population doublings in the condition provided by AcceGen Biotech Research Laboratories.