CD1A and psoriasis: A reduction in CD1a expression is indicative of DC maturation, and DCs isolated from plaques of psoriasis have previously been demonstrated to possess a mature phenotype, in terms of a loss of CD1a.23 CD1a is decreased in mLCs derived from healthy controls that have been incubated with the supernatants of cultured keratinocytes isolated from plaques of psoriasis, compared with keratinocytes isolated from healthy skin.24 This indicates that an alteration in the skin microenvironment in patients with psoriasis is able to influence LC biology.