Skin homing (cutaneous lymphocyte-associated antigen-positive) CD8(+) T cells respond to superantigen and contribute to eosinophilia and IgE production in atopic dermatitis

In allergic inflammations of the skin, activation of CD4(+) T cells was dem onstrated to play an important role; however, a minor role for CD8(+) T cel ls is implied. In the present study, we compared cutaneous lymphocyte-assoc iated Ag (CLA)-expressing CD4(+) and CD8(+) subsets, which were isolated fr om peripheral blood and lesional skin biopsies in atopic dermatitis (AD) pa tients. We demonstrated that CD8(+)CLA(+) T cells proliferate in response t o superantigen and are as potent as CD4(+)CLA(+) T cells in IgE induction a nd support of eosinophil survival. In atopic skin inflammation, the existen ce of high numbers of CD4(+) and AD8(+) T cells was demonstrated by immunoh istochemistry and by culturing T cells from skin biopsies, In peripheral bl ood, both CD4(+) and CD8(+) subsets of CLA(+)CD45RO(+) T cells were in an a ctivated state in AD. The in vivo-activated CLA(+) T cells of both subsets spontaneously released an IL-5- and IL-13-dominated Th2 type cytokine patte rn. This was confirmed by intracytoplasmic cytokine staining immediately af ter isolation of the cells from peripheral blood. In consequence, both CD4( +) and CD8(+), CLA(+) memory/effector T cells induced IgE production by B c ells mainly by IL-13, and enhanced eosinophil survival in vitro by delaying eosinophil apoptosis, mainly by IL-5, These results indicate that in addit ion to the CD4(+) subset, the CD8(+)CLA(+) memory/effector T cells are capa ble of responding to superantigenic stimulation and play an important role in the pathogenesis of AD.