Remodelling of the CD8 T-Cell Compartment in the Elderly

What is it about?

Immunosenescence is a complex series of alterations that affect most aspects of immunity, including innate and adaptive immunity and is dependent not only on chronological ageing itself, but also on exogenous factors such as persistent antigenic stress leading to chronic activation of the immune system. The most significant changes occur in the T-cell compartment, with decreasing naïve cells and increasing numbers of cells with a memory/activated phenotype. T-cells from elderly individuals also show altered responsiveness to antigen and display altered profiles of cytokine production when compared to T-cells from young individuals.

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Why is it important?

The most characteristic changes of the CD8 compartment associated with ageing are the accumulation of CD8+CD28null T-cells, antigen receptor repertoire shrinkage, increased expression of NK-associated receptors and the downregulation of CCR7 and CD45RA, suggesting an expansion of T-cells with an effector-memory 2 phenotype. These changes can be explained by the reduction of naïve CD8+ T-cell-output, due to age-associated thymus involution and the oligoclonal expansion of CD8+ T-cells, likely as a consequence of persistent viral infections. The role of cytomegalovirus in the oligoclonal accumulation of CD8+CD28null T-cells has been recently stressed