[The immune response against microbial infections in the skin--weak in atopic dermatitis and strong in psoriasis]. / Ihon mikrobipuolustus: heikko atopiassa ja vahva psoriaasissa.

The innate and adaptive immune responses have been better understood after the discovery of Toll-like receptors (TLRs), antimicrobial peptides and different populations of dendritic cells. In the skin there are 1 million T-cells per 1 cm2 and 20 billion in total. Naive T-cells activated by antigen-presenting cells can polarize in four directions and they express homing receptor CLA for operating in the skin when the antigen is first detected in the skin area. In psoriasis Th17 activation increases antimicrobial peptides. The IL-23/Th17 axis is largely absent in atopic dermatitis and may result in infections.