[How does eczema arise?].

New experimental results on the role of T cells and keratinocytes have led to a better understanding of eczematous inflammation and can help explain both the clinical and histological pictures of eczema. Besides activated endothelial cells and adhesion molecules, a complex interaction of numerous chemokines controls the recruitment of T cells from the blood vessels and their migration into the dermis and epidermis. Activated T cells damage the epidermis by pro-inflammatory cytokines and can induce apoptosis of individual keratinocytes through "killer molecules". Cleavage of adhesion molecules on keratinocytes leads to spongiotic changes. Keratinocytes then activate repair mechanisms, which cause acanthosis and parakeratosis in chronic eczema.