House dust mite antigen is a well-known allergen in the pathogenesis of atopic dermatitis (AD), a chronic relapsing inflammatory skin disease. We evaluated the AD model mice sensitized with house dust mite antigen and observed a Th2-dominant immune response. In this experiment, BALB/c mice were sensitized percutaneously with house dust mite antigen three times with 7 days interval after skin barrier disruption. A remarkable infiltration of polymorphonuclear granulocytes and monocytes in the cutis was observed in mice treated with this antigen, high serum IgE levels and IL-4 mRNA expression in local lymph node cells was also observed. CD19(+) B cell numbers overturned to CD4(+) helper T cells. In these mice, there was significant increase of B7.2 (CD86) expression on CD19(+) B cells. These results indicate that house dust mite antigen sensitizes BALB/c mice and skews their Th1/Th2 balance toward Th2. (C) 2002 Elsevier Science B.V. All rights reserved.