Abstract • 80

Erythema Toxicum Neonatorum is a benign rash, present in all newborn infants to various degree, of still unknown etiology. We performed indirect immunohistochemistry studies of a punch biopsy from a cutaneous lesion in ten 1-day old infants with specific monoclonal antibodies directed against adhesions molecules, cytokines, chemokines and cell-type specific membrane markers. Immunohistological staining demonstrated a strong expression of the adhesion molecule E-Selectin in the vessel walls and the presence of large numbers of inflammatory cells, identified as macrophages (Mac 387+,CD14+) dendritic-like cells (CD40+,CD83+,HLA-DR+), neutrophils (CD15+), eosinophiles (EG2+). Langerhans cells (CD1a+), present in the lesions and above the basal layer of the epidermis, strongly expressed HLA-DR. The lesions also contained large amounts of the pro-inflammatory cytokines IL-1α and IL-1β and the chemokine IL-8. We conclude that the recruitment and activation of immunological cells in the skin, regulated, at least in part by E-Selectin and IL-1 and IL-8, constitutes the first line of defense against microorganisms and enables the newborn infant to protect itself against the rapidly colonizing microflora. From an evolutionary point of view, this reaction has most probably been of great importance for surveillance.