As a member of the dendritic cell (DC) family, Langerhans cells (LC) play key roles in the induction of T cell-mediated immune responses in skin. During antigen presentation, LC deliver activation signals to T cells and, at the same time, undergo maturational changes. The long-term objectives are to study molecular mechanisms regulating various changes that accompany T cell-dependent terminal maturation of LC and to develop new immuno-modulatory strategies that are designed to control bi-directional LC-I cell interaction.
The specific aims are: 1) To define functional roles played by chemokines and chemokine receptors in LC migration. To test the hypothesis that mature LC can be """"""""entrapped"""""""" by an artificial chemokine gradient created in their migratory path and loaded with antigen, ethylene-vinyl-acetate (EVA) polymer particles releasing MIP-3B and OVA (model antigen) will be implanted s.c. in mice. Induction of OVA-specific responses will validate the efficacy of this in situ LC vaccine strategy. To test the second hypothesis that efficacy of DC vaccines can be improved by promoting DC homing, CCR7 DNA-transfected """"""""bullet"""""""" DC will be examined for their homing property and the ability to induce anti-tumor protective immunity. 2) To study the expression and function of a novel anti-apoptotic factor (AIM) in antigen presentation. Preliminary results suggest that LC produce a recently identified anti-apoptosis factor AIM during antigen presentation, which, in turn, determines the magnitude and kinetics of cellular immune responses by preventing premature apoptosis of LC and I cells. These hypotheses will be tested at cellular and animal levels using anti-AIM mAb, recombinant AIM, AIM-deficient mice, AIM-transgenic mice, and AIM cDNA-transduced """"""""super"""""""" DC. 3) To determine the molecular identity and functional roles of ecto-ATPase and ADPase activities on LC. Preliminary results suggest that CD39 is responsible for ecto-ATPase and ADPase activities on LC and that LC-associated CD39 plays dual functions, i.e., a protective role against chemically induced skin inflammation and an immuno-regulatory role in antigen presentation. These hypotheses will be tested by studying CD39 expression and heterogeneity in LC, ATP and ADP release by keratinocytes upon exposure to irritant chemicals and by T cells during antigen presentation, the magnitude and kinetics of irritant vs allergic contact hypersensitivity responses in CD3 9-deficient mice, and biological impacts of CD39 agonists vs antagonists.
These aims, which may first appear to be mutually independent, are highly related each other (e.g., G-protein coupled receptor signaling via chemokine receptors and P2Y receptors, and counter-regulation of apoptosis by AIM and P2X receptors). Thus, the present study will uncover dynamic and complex regulation of LC function, thus, forming both technical and conceptual bases for the development of novel immuno-regulatory and/or anti-inflammatory strategies and for their applications to skin cancer and inflammatory skin disease.
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