There are many cell free factors which are associated with an inflammatory response which are able to be induced in older animals and which are expressed at higher levels than seen in younger mice. The biologic implications of this finding are very important and demonstrate that the immune deficiency of aging is not a simple loss of function or cells but a change in the control of cellular function. The expression of receptors for the factors as well as an analysis of their ability to generate cellular signals in the cells from young and old mice will provide evidence for the biologic role of these factors in the older individuals.
