Irritant contact dermatitis is an important cause of morbidity and time loss in occupational and home environments. As yet, no useful in vitro assays can predict the irritancy of chemical compounds. Recent studies demonstrate that although irritant contact dermatitis and its companion disease, allergic contact dermatitis, have different origins (specific immunologic recognition versus non-specific inflammation), their pathologic mechanisms are similar, and both include the activation of numerous genes. Our hypothesis is that a unique set of genes is activated by topical application of irritant compounds. Thus, activated gene expression profiles ("genetic fingerprints") can be used to characterize pathogenic mechanisms, and this new knowledge will allow us to develop in vitro assays that assess chemical irritancy. We will: 1) employ a "MicroChip/MicroArray" to examine expression of relatively large numbers (> 18,000) of genes in mouse skin after application of compounds known to be irritants (and allergens). These genes will be termed the genetic fingerprints of irritant (and allergic) contact dermatitis. 2) identify the cells in skin that are responsible for the expression of fingerprint genes by examining keratinocytes, Langerhans cells, and epidermal y8 T cells from experimentally induced dermatitis using a "Laser Capture Micro-dissection System." 3) isolate 5' promoter regions from the 5-20 fingerprint genes that are highly activated by each of three irritant chemicals (sodium lauryl sulfate, oxazolone, and dinitrofluorobenzene), in three mouse strains (Balb/c, CBA, and C57/BL6). 4) introduce luciferase (Luc) reporter constructs containing promoters for each of the identified genes into long-term epidermal cells lines (Langerhans cell, keratinocytes, and y8 T cell). 5) treat transfectants in vitro with selected irritant chemicals , and measure Luc activities. 6) validate the reliability, sensitivity, and reproducibility of transfectants in vivo using a battery of common irritant compounds. These studies will provide important new knowledge about irritant and allergic contact dermatitis, and they will address the programmatic request for novel methods to identify irritants prior to their introduction into the workplace.