Mechanisms of reduced T cell imunity in older adults

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Aging is accompanied by a marked susceptibility to infectious diseases, which inflict heavy toll upon the rapidly aging society with regard to lost productivity, mounting health costs and loss of life. The progressive decline with age of the immune system - immunosenescence - is the primary underlying cause of the age-related increase in this susceptibility. Despite decades of research, important gaps remain in our understanding of the fundamental nature of the process, as well as in our practical ability to protect older adults against infectious diseases. Some of the key gaps in knowledge result from the insufficient integration of the available models in which to research immunosenescence, and incomplete validation of the relevance of obtained data to the human aging. Specifically, the two most popular and most relevant models - the (immuno)genetically versatile and easily manipulated mouse model; and the ethically much more complex and experimentally limited, but physiologically supremely relevant human model, have provided data that is insufficiently compatible with one another thus far. This proposal seeks to reduce this gap by taking advantage of the newly developed human model by one of the co-applicants, to study memory T cell response in the skin of healthy young and old donors. Our recent human studies had identified a significant defect in the ability of old subjects to mount an eficient immune response in the skin. However this is not a global deect as the white cells from the blood of the same individuals can respond to the same microbial product that was injected in the skin. However the actual manipulation of the cells that are defective in the skin cannot be performed in humans due to ethical constraints. Furthermore, it is not possible to test whether we can enhance the responses of these cells by directly targeting cell surface activatory receptors (Toll receptors) on the cell that is defective called macrophagethe in vivo. We propose to further develop in depth this model in humans and to broaden, enhance and complement the data generated by the parallel use of mechanistic studies in the aged mouse model of skin immunity that will be performed in close partnership with Dr. Janko Nikolich-Zugich at the University of Arizona. Thus we will develop he same skin challenge experimental system in the mouse that we can manipulate to attempt to boost immunity in he skin in old animals. During the preparation of this proposal, Dr Akbar had visited Tucson in late November, 2008, and Dr. Nikolich travelled to London in February 2009 to organize the aims and strategy for this application. From the intense discussions and joint efforts, we have developed a synergistic experimental strategy, whereby incisive, cutting-edge studies in humans will be linked to parallel investigations in mice to enable the manipulation of the ageing immune system in vivo to determine if we can reverse the cutaneous defect in cutaqneous immunity that develops during ageing.