P#01   Onset of alopecia areata in C3H/HeJ mice involves transient, high expression of CD44 variant isoforms and low CD4+/CD25+ suppressor cell activity

Kevin J. McElwee1, Margot Zöller2, Peter Engel2 and Rolf Hoffmann1. 1Dept of Dermatology, Philipp University, Marburg, Germany; 2Dept of Tumor Progression and Tumor Defense, German Cancer Research Center, Heidelberg

Alopecia areata (AA), a suspected autoimmune disease of anagen stage hair follicles, AA can be induced in normal haired C3H/HeJ mice by grafting AA-affected skin from littermates. Standard CD44s and CD44 isoforms are adhesion molecules required for leukocyte extravasation during inflammatory processes. CD4+/CD25+ cells are known to be important for T cell homeostasis. By flow cytometry, we examined skin and lymph node expression levels of cytokines, CD44 variant isoforms, CD4, CD25, and other cell surface molecules, at 2, 6, and 12 weeks post grafting as compared to sham grafted mice, normal haired mice and chronic AA affected mice. Leukocytes in the skin of mice 2 weeks after transplanting AA affected skin highly expressed CD44v3, CD44v6, CD44v7 and CD44v10 as compared to sham grafted control mice. By 12 weeks, expression of CD44 isoforms had returned to normal. With chronic AA expression, CD44s and CD44v6 were slightly elevated, but expression of CD44v3 was reduced. CD4+/CD25+ cells were present in significantly reduced numbers in mice grafted with AA-affected skin both at 2 weeks after grafting and in chronic AA-affected mice as compared to controls. In association, CD40 and CTLA-4 expression was reduced. Expression of cytokines IL-2, IL-4, IL-6, IL-10 and IL-12 was elevated in mice receiving AA affected skin at all times whereas sham grafted mice exhibited only transient increases post surgery. Taken together, expression of CD44 variant isoforms appears most important for the migration of leukocytes during the initial onset of AA, but is less significant in maintenance of the disease state that is characterized by high cytokine production levels and an increased number of CD4+ and CD8+ cells. The low level of CD4+/CD25+ cells, CD40 and CTLA-4 in the skin of AA-affected mice are in support of AA as an autoimmune disease on the basis of an altered regulation of immune cell homeostasis.