Immunologic abnormalities exhibited in IL-7 transgenic mice with dermatitis

Interleukin (IL)-7 transgenic mice, which we established previously, developed severe dermatitis characterized by massive infiltration of γδ T cells in the dermal lesion. To fully understand the pathology of this intriguing skin disease, we examined several immunologic features of dermis infiltrating lymphocytes from the lesional skin of IL-7 transgenic mice. We observed a moderate response to mitogens, a poor response to alloantigens, and the absence of cytotoxic activities to several tumor cell lines and skin derived cells regardless of the presence of IL-2 or IL-7. On the other hand, dermis infiltrating lymphocytes could proliferate with exogenous IL-2 and IL-7. Moreover, reverse transcriptase polymerase chain reaction and fluorescence activated cell sorter analysis revealed that dermis infiltrating lymphocytes expressed various cytokines including IL-4 and IL-7, and several activation markers for T cells (CD44, CD69, IL-2Rα), in addition to IL-7Rα. In the sera of the affected mice, hyper e-globulinemia was observed. These findings suggested that dermis infiltrating lymphocytes proliferated in an activated state in the skin lesion in an autocrine and/or paracrine manner and produced Th2 type cytokines that might evoke immunologic abnormalities. This study and previous findings suggest that IL-7 transgenic mouse with dermatitis offer the potential of serving as a useful tool for investigating the immunologic role of cutaneous γδ T cells, especially their participation in IgE production in vivo .