Ageing is associated with an increase in the incidence and severity of many infectious diseases. The most common infections in the elderly are influenza, infections with Streptococcus pneumoniae, infections of the skin and also of the urogenital tract [
1]. In addition, reactivation of latent viruses and bacteria such as Varicella-Zoster-Virus leading to Herpes zoster [
2,
3] and Mycobacterium tuberculosis [
4,
5] are more frequent in old age. This may be due to decreased immunosurveillance as well as to other factors such as age-associated diseases, poor nutrition, chronic renal failure and institutionalization.
Cytomegalovirus (CMV) is a human beta-herpesvirus with a prevalence of 60–100% in the adult population. The link between CMV-infection, immunosenescence and longevity has recently been a subject of great interest [
6,
7]. Despite frequent reactivation of latent CMV in the elderly as suggested by increased anti-CMV antibodies and viral shedding in the urine [
8] there are no reports about overt CMV-disease in immunocompetent elderly persons. T cells are essential for the control of viral replication, spread and disease [
9‐
12]. In CMV-seropositive elderly persons up to 25% of the total CD8
+ T cell pool can be specific for CMV with the epitope NLVPMVATV of the pp65 matrix protein (CMV
NLV) being immunodominant [
13]. These CMV-specific cells show a highly differentiated effector phenotype [
14‐
16] and express markers for cytotoxicity [
14,
16]. They are proinflammatory [
16], and to a high degree clonally expanded [
13,
17,
18]. This has led to the suggestion that CMV-specific T cell clones take up a lot of space and may therefore be responsible for the loss of T cells of other specificities, such as for instance for Epstein-Barr virus (EBV) [
19]. The proinflammatory properties of the steadily increasing number of CMV-specific T cells may represent an additional problem, as age-related subclinical inflammatory processes termed "inflamm-ageing" can be enhanced [
20]. Inflammation is known to support the development and progression of age-related diseases such as for instance Alzheimer's disease [
21]. In longitudinal studies on octo- and nonagenerians CMV-seropositivity has also been linked to the so-called "immune-risk phenotype" and with increased mortality [
22,
23].
Despite the obvious importance of CMV infection in old age little is known about the clonal composition of CMV-specific T cells in apparently healthy elderly persons. We therefore analyzed the clonal composition of CD8
+ T cells, which are specific for the HLA-A*0201-restricted, immunodominant pp65-derived epitope NLVPMVATV [
24,
25] in persons of different age.