Exceptional aging has been defined as maintenance of physical and cognitive function beyond the median lifespan despite a history of diseases and/or concurrent subclinical conditions. Since immunity is vital to individual fitness, we examined immunologic fingerprint(s) of highly functional elders. Therefore, survivors of the Cardiovascular Health Study in Pittsburgh, Pennsylvania, USA were recruited (n = 140; mean age = 86 years) and underwent performance testing. Blood samples were collected and examined blindly for humoral factors and T cell phenotypes. Based on results of physical and cognitive performance testing, elders were classified as “impaired” or “unimpaired”, accuracy of group assignment was verified by discriminant function analysis. The two groups showed distinct immune profiles as determined by factor analysis. The dominant immune signature of impaired elders consisted of interferon (IFN)-γ, interleukin (IL)-6, tumor necrosis factor-α, and T cells expressing inhibitory natural killer-related receptors (NKR) CD158a, CD158e, and NKG2A. In contrast, the dominant signature of unimpaired elders consisted of IL-5, IL-12p70, and IL-13 with co-expression of IFN-γ, IL-4, and IL-17, and T cells expressing stimulatory NKRs CD56, CD16, and NKG2D. In logistic regression models, unimpaired phenotype was predicted independently by IL-5 and by CD4+CD28nullCD56+CD57+ T cells. All elders had high antibody titers to common viruses including cytomegalovirus. In cellular bioassays, T cell receptor (TCR)-independent ligation of either CD56 or NKG2D elicited activation of T cells. Collectively, these data demonstrate the importance of immunological parameters in distinguishing between health phenotypes of older adults. NKR+ T cells and cytokine upregulation indicate a unique physiologic environment in old age. Correlation of particular NKR+ T cell subsets and IL-5 with unimpaired performance, and NKR-driven TCR-independent activation of T cells suggest novel immunopathway(s) that could be exploited to improve immunity in old age.

Objectives CD8T cells lacking CD28 were originally reported by Wedderburn and colleagues as a characteristic feature of JIA, but the relevance of these unusual cells to JIA remains to be elucidated. Because of recent evidence that CD28 loss is typical of terminally differentiated lymphocytes, we examined for functional subsets of CD8T cells in JIA. Methods Following informed consent/assent, blood and/or waste synovial fluid were collected from children with definite diagnosis of JIA (n = 98). De-identified blood (n = 33) and cord blood (n = 13) samples from healthy donors were also collected. CD8T and CD4T cells were screened for novel receptors, and where indicated, bioassays were performed to determine functional relevance of the identified receptor. Results Patients had a naïve T cell compartment with shortened telomeres, and their entire T cell pool had reduced proliferative capacity. They had an over abundance of CD31+CD28null CD8T cells, which was a significant feature of oligoarticular JIA (n = 62) compared to polyarticular JIA (n = 36). CD31+CD28null CD8T cells had limited mitotic capacity, and expressed high levels of the senescence antigens γH2Ax and/or p16. Ligation of CD31, independent of the TCR, sufficiently induced tyrosine phosphorylation, vesicle exocytosis, and production of IFN-γ and IL-10. Conclusion These data provide the first evidence for cell senescence, represented by CD31+CD28null CD8T cells, in the pathophysiology of JIA. Activation of these unusual cells in a TCR-independent manner suggests they are maladaptive, and could be potential targets for immunotherapy.

As the repertoire of αβT cell receptors (TCR) contracts with advancing age, there is an associated age-dependent accumulation of oligoclonal T cells expressing of a variety of receptors (NKR), normally expressed on natural killer (NK) cells. Evidences for differential regulation of expression of particular NKRs between T cells and NK cells suggest that NKR expression on T cells is physiologically programmed rather than a random event of the aging process. Experimental studies show NKRs on aged αβT cells may function either as independent receptors, and/or as costimulatory receptors to the TCR. Considering the reported deficits of conventional αβTCR-driven activation and also functional deficits of classical NK cells, NKR + αβT cells likely represent novel immune effectors that are capable of combining innate and adaptive functions. Inasmuch as immunity is a determinant of individual fitness, the type and density of NKRs could be important contributing factors to the wide heterogeneity of health characteristics of older adults, ranging from institutionalized frail elders who are unable to mount immune responses to functionally independent community-dwelling elders who exhibit protective immunity. Understanding the biology of NKR + αβT cells could lead to new avenues for age-specific intervention to improve protective immunity.