[Immunologic aspects of aging]

Aging and Inflammation

Aging can be conceptualized as the progressive disequilibrium between stochastic damage accumulation and resilience mechanisms that continuously repair that damage, which eventually cause the development of chronic disease, frailty, and death. The immune system is at the forefront of these resilience mechanisms. Indeed, aging is associated with persistent activation of the immune system, witnessed by a high circulating level of inflammatory markers and activation of immune cells in the circulation and in tissue, a condition called "inflammaging." Like aging, inflammaging is associated with increased risk of many age-related pathologies and disabilities, as well as frailty and death. Herein we discuss recent advances in the understanding of the mechanisms leading to inflammaging and the intrinsic dysregulation of the immune function that occurs with aging. We focus on the underlying mechanisms of chronic inflammation, in particular the role of NF-κB and recent studies targeting proinflammatory mediators. We further explore the dysregulation of the immune response with age and immunosenescence as an important mechanistic immune response to acute stressors. We examine the role of the gastrointestinal microbiome, age-related dysbiosis, and the integrated stress response in modulating the inflammatory "response" to damage accumulation and stress. We conclude by focusing on the seminal question of whether reducing inflammation is useful and the results of related clinical trials. In summary, we propose that inflammation may be viewed both as a clinical biomarker of the failure of resilience mechanisms and as a causal factor in the rising burden of disease and disabilities with aging. The fact that inflammation can be reduced through nonpharmacological interventions such as diet and exercise suggests that a life course approach based on education may be a successful strategy to increase the health span with few adverse consequences.

Aging and Options to Halt Declining Immunity to Virus Infections

Immunosenescence is a process associated with aging that leads to dysregulation of cells of innate and adaptive immunity, which may become dysfunctional. Consequently, older adults show increased severity of viral and bacterial infections and impaired responses to vaccinations. A better understanding of the process of immunosenescence will aid the development of novel strategies to boost the immune system in older adults. In this review, we focus on major alterations of the immune system triggered by aging, and address the effect of chronic viral infections, effectiveness of vaccination of older adults and strategies to improve immune function in this vulnerable age group.

Cytomegalovirus Infection and Memory T Cell Inflation

Cytomegalovirus (CMV) infection in healthy individuals is usually asymptomatic and results in latent infection. CMV reactivation occasionally occurs in healthy individuals according to their immune status over time. T cell responses to CMV are restricted to a limited number of immunodominant epitopes, as compared to responses to other chronic or persistent viruses. This response results in progressive, prolonged expansion of CMV-specific CD8⁺ T cells, termed 'memory inflation'. The expanded CMV-specific CD8⁺ T cell population is extraordinarily large and is more prominent in the elderly. CMV-specific CD8⁺ T cells possess rather similar phenotypic and functional features to those of replicative senescent T cells. In this review, we discuss the general features of CMV-specific inflationary memory T cells and the factors involved in memory inflation.

Bioanalysis of age-related changes of lipid metabolism in nonagenarians

The aim of the present study was the bioanalysis of lipid metabolism in the aged patients and to study the relationship between these biochemical markers and longevity. Eleven nonagenarians, nine women and two men, aged 94+/-3 years and ten control patients, six women and four men, aged 84+/-5 years, followed at the Department of Metabolic Care and Gerontology, Charles University, Teaching Hospital entered the study. All subjects were self-sufficient, without major illnesses and free living. At the start of the project the free fatty acids (FFA), thiobarbituric reactive substances (TBARS), retinol, alpha tocopherol, ascorbic acid, cholesterol, triacylglycerols, phospholipids in serum, in lipoprotein fractions and fatty acids (FA) and phospholipids in erythrocyte membrane were determined. We used capillary gas chromatography for determination of fatty acids. Retinol and alpha tocopherol were analysed by reversed-phase high-performance liquid chromatography, other parameters were determined spectrophotometrically or spectrofluorometrically. We found significantly higher LDL polyunsaturated fatty acids (PUFA) 22:4n--3 (P=0.028) and 22:6n--3 (P=0.018) and a significant increase of HDL alpha tocopherol/cholesterol ratio (P=0.034) in nonagenarians. There were not any significant differences in erythrocyte membrane fatty acids and phospholipids. In serum we found significantly higher level of TBARS (3.22+/-1.22 vs 1.98+/-0.71 micromol/l, P=0.012) in nonagenarians, other parameters were not changed significantly. The higher concentration of PUFAs in LDL and alpha tocopherol in HDL might be parameters related to longevity.

Effect of selective ultraviolet phototherapy on DNA and antinuclear antibody titers in psoriatic patients

The sera of 21 psoriatics treated by selective ultraviolet phototherapy (SUP) for 1-7 months were screened for IgG- and IgM-anti-DNA antibodies and antinuclear antibodies (ANAs) by standardized ELISA and the indirect immunofluorescence technique. No patients developed IgG-antibodies against native DNA under SUP, but two patients increased their IgM-antibody titers five- and tenfold, respectively. The IgG- and IgM-anti-single-stranded-(ss)DNA antibody titers remained unaltered in 38% and 57% of the patients. In 43% and 24%, respectively, they rose to a maximum of three times their original; and in 20% they decreased to a minimum of 40% of their pretherapeutic titers. After 1 month therapy no patient had produced ANAs, but all three patients showing ANAs before therapy had increased titers (one titer step). These remained on the elevated level or were even further increased by one-titer step during progressive therapy. Two patients out of 14 developed low titers of IgM-(1:20) or IgA-(1:40)ANAs against deoxyribonucleoprotein (DNP), initially after 3 months of irradiation; in one of them IgG-ANAs (titer 1:10) against DNP were additionally formed after 6 months of therapy. Our results suggest that lesions in DNA and DNP generated by SUP trigger an immune response to nuclear antigens.

Brain-reactive antibodies in sera of aging non-human primates

Previous studies in our laboratory demonstrated an age-related increase in the brain-reactive antibodies in sera of aging mice. The present paper deals with the study of brain-reactive antibodies in sera of non-human primates (Macaca nemestrina) of three age groups (4, 10 and 20 years) by an indirect immunofluorescence method. The results indicated a progressive increase in the serum levels of these antibodies with advancing age. Since all three age groups examined demonstrated brain-reactive antibodies in sera, the age of onset of these antibodies could not be determined in these animals. It has been suggested that the formation of these antibodies could be evidence of autoimmune reactions which might play a significant role in neuronal degeneration during aging.