Phenotypic and Functional Changes of Circulating Monocytes in Elderly

Immunosenescence has been envisaged as a situation in which the specific immune system deteriorates with age, while the innate immunity is negligibly affected and, in some cases, almost upregulated. Ageing represents a state of paradox where chronic inflammation is associated with declining immune responses. This peculiar finding, known as inflammageing, is mainly sustained by cells of the innate immunity. One of the key constituents of the innate immune system are monocytes. Therefore, although the age-related changes in the specific immunity are commonly considered the hallmarks of immunosenescence, the central role of the complex remodelling of first line defence cells, such as monocytes, is gradually emerging. For example, chemotaxis and phagocytosis, as well as antigen processing and presentation, are depressed, whereas cell activation and the secretion of inflammatory cytokines, such as IL-1, IL-6, TNF, are markedly increased. Changes in the expression of functionally important cellular receptors on monocyte surface can also contribute to the modification of immune function characteristic of the elderly.