Vasoactive intestinal polypeptide in allergic contact dermatitis: an immunohistochemical and radioimmunoassay study

Vasoactive intestinal polypeptide (VIP) is a neuropeptide with immunomodula tory properties, To elucidate the possible role of VIP in the pathophysiolo gy of cutaneous contact hypersensitivity, we compared involved with uninvol ved skin of allergic contact dermatitis (ACD) from nickel-allergic patients . Assays included quantification of VIP-immunoreactive (VIP-IR) nerve fibre s and cells bearing immunoreactivity for VIP1 and VIP2 receptors in skin bi opsy specimens, and of the concentration of VIP-like immunoreactivity (VIP- LI) in extracts of biopsy specimens. VIP-IR nerve fibres were found in the deeper part of the dermis close to sweat glands and hair follicles, No diff erence in the presence of VIP-IR nerve fibres was found between involved an d uninvolved skin of ACD, VIP1 and VIP2 receptor immunoreactivity was seen on keratinocytes in the basal layer of the epidermis, with no difference be tween involved and uninvolved skin. Staining was also seen on vessel waifs and mononuclear cells in the dermis, The highest staining intensity in the mononuclear cells was noted with the antibodies against the VIP2 receptor. While most of the mononuclear cells were stained in uninvolved skin, a mino rity of the cells showed a positive signal in involved skin. The concentrat ion of VIP-LI in uninvolved skin was 1.53 +/- 0.790 pmol/g and in involved skin 1.41 +/- 0.735 pmol/g, It is concluded that there is no significant di fference in either the distribution of VIP-IR fibres or the concentration o f VIP-LI between involved and uninvolved skin of ACD, However, the number o f dermal mononuclear cells showing VIP2 receptor immunoreactivity in skin o f ACD was reduced.