BIPHASIC RESPONSE AGAINST AEROALLERGEN IN ATOPIC-DERMATITIS SHOWING ASWITCH FROM AN INITIAL T-H2 RESPONSE TO A T-H1 RESPONSE IN-SITU - AN IMMUNOCYTOCHEMICAL STUDY

In the pathogenesis of atopic dermatitis (AD), IgE plays an important role; and T-H2 cells. producing IL-4, have been ascribed a key role in allergic diseases such as AD. To investigate the role of T-H subpopul ations in the onset and continuation of AD, we performed atopy patch t ests (APTs) with house dust mite allergen in patients with AD. Punch b iopsy specimens were taken from the APT site, and sections were immuno cytochemically double-stained for IL-4 and interferon-gamma together w ith different membrane markers. This provides a unique model for study ing the kinetics of the TH0, T-H1, and T-H2 responses in situ. The res ults show that in lesional skin interferon-gamma-positive cells predom inate over IL-4-positive cells. The interferon-gamma-positive cells ar e mainly CD3(+) and, in particular, CD4(+) cells; the remainder are CD 8(+), RFD-1(+), and RFD-7(+) cells. The IL-4-positive cells are exclus ively CD4(+) T cells; no eosinophils or mast cells were found to stain for IL-4. With regard to the T-H cell response, a clear dichotomy of the eczematous response to allergen in skin was observed. In the initi ation phase IL-4 production by T-H2 and T-H0 cells is predominmant ove r interferon-gamma production by T-H1 and T-H0 cells. In the late and chronic phases the situation is reversed and interferon-gamma producti on by T-H1 and T-H0 cells predominates over IL-4 production by T-H2 an d T-H0 cells. Understanding of the relationship between the observed b iphasic response and clinical manifestation of Ad is important for the development of therapeutic strategies.