Interleukin-4 and the interleukin-4 receptor in allergic contact dermatitis

Cutaneous immune responses involving T helper (TH) type 1 (TH1) and type 2 (TH2) T cells, characterised by secretion of interferon-gamma (Ifn-gamma) and interleukin-4 (IL-4), respectively, have both been reported in allergic contact dermatitis (ACD). We used immunohistochemistry to localize expression of IL-4 in ACD lesions and unaffected skin. Atopic dermatitis (AD) and psoriasis biopsies provided positive and negative IL-4 immunoreactivity controls. To investigate the role of IL-4 in ACD, we investigated expression of IL-4 receptors in ACD, AD and psoriatic skin. IL-4 immunoreactivity was found in cells in the dermal infiltrate in 3 out of 7 ACD lesions, but not in unaffected skin from these patients. IL-4 immunoreactivity was found in the dermal infiltrate of all lesional and unaffected AD biopsies, but in none of the psoriatic biopsies. IL-4 receptor alpha chain immunoreactivity, associated with dermal mast cells, was found in all patients. Local expression of IL-4 in ACD indicates either TH2 or TH0 immunoregulation in some allergic contact dermatitis lesions. Our findings do not support exclusive TH1 or TH2 cutaneous immune responses in ACD. Expression of IL-4 receptors by cutaneous mast cells provides a route through which local effects of IL-4 might be mediated.