Skin infections make a substantial contribution to the total burden of infectious disease worldwide. In addition to their role as primary pathogens many organisms aggravate inflammatory skin conditions such as atopic eczema or contribute to the delayed healing of chronic ulcers and infected surgical wounds. Natural antibiotics are evolutionarily conserved peptides with broad antimicrobial activity which contribute to the innate resistance of insects, plants, and mammals to invading pathogens. 1 Antimicrobial peptides of the defensin family with broad activity against gram-negative bacteria, fungi, mycobacteria, and enveloped viruses have been isolated from neutrophil granules, macrophages, and some specialised epithelial cells of the small intestine. 1 With a combination of PCR and in-situ hybridisation we have identified and localised expression of a member of the defensin family to keratinocytes in normal human skin.

Human beta defensin 1 (HBD1) is a recently identified antimicrobial peptide. 2 We investigated the expression of HBD-1 in normal human skin by RT-PCR and in-situ hybridisation to determine if this gene is expressed and the distribution of transcripts within the epidermis. RT-PCR amplified the predicted 290 bp fragment from normal skin and cultured keratinocytes using HBD1 specific primers (primer 1 5'TCTGTCAGCTCAGCCTC; primer 2 5'CTCTCAGCTCACTTGCAG). For in-situ hybridisation the 290 bp fragment was amplified using the same primers with restriction sites linked onto the 5'ends and directionally cloned into pBluescript. Specificity of the cloned probe was confirmed by restriction analysis. In-situ hybridisation of paraffin sections of paraformaldehyde fixed