Biology of longevity: role of the immune system
G. Colonna-Romano, G. Candore, A. Aquino, M. Bulati, S. Vitello, D. Lio, I.M. Rea, C. Caruso
Gruppo di Studio sull'Immunosenescenza, Dipartimento di Biopatologia e Metodologie Biomediche, Università di Palermo, Corso Tukory 211, 90134 Palermo
Ageing is an inexorable intrinsic process that affects all cells,
tissues, organs and organisms. In fact, humans, as well as the other
animals, are designed as a compromise to guarantee optimal survival
until the time of reproduction based on natural selection that is
effective until that age, so the post-reproductive physiology of an
organism (i.e., ageing) is an epigenetic and pleiotropic manifestation
of the optimisation for early fitness. The progressive decrease in
physiological capacity and the reduced ability to respond to stresses
lead to increased susceptibility and vulnerability to diseases. Thus,
mortality due to all causes increases exponentially with ageing.
Improvement of hygiene, preventive and curative medicine as well as
socio-economic developments have led to an increase of the human mean
life expectancy that allows ever larger proportions of the population
to reach an age that is far beyond that of the reproductive phase, but
the maximum lifespan potential (MSLP) has remained constant. Besides,
MLSP appears to be species specific, implying a significant genetic
component to the rate of ageing. Evolutionary theory and empirical
evidence suggest that ageing is a process of gradual accumulation of
damage in cells and tissues of the body. Thus, genes implied in
ageing and longevity are implied in the network of cell maintenance
systems, including immune system genes. In fact, longevity may be
correlated with optimal functioning of the immune system and the ageing
of immune system, immunosenescence, is the consequence of the
continuous attrition caused by chronic antigenic overload. Some of the
most important characteristics of adaptive immunity in ageing are
compatible with this assumption. Concomitantly, the antigenic load
results in the progressive generation of inflammatory responses
involved in age-related diseases. Most of the parameters affected by
immunosenescence appear to be under genetic control, and research is
addressing this point. So, immunosenescence fits with basic
assumptions of evolutionary theories of ageing, such as antagonistic
pleiotropy. In fact, the immune system, by neutralizing infectious
agents, plays a beneficial role until the time of the reproductions and
parental cares, but, by determining a chronic inflammation, can play a
detrimental one late in life, in a period largely not foreseen by
evolution.
Key words:
Centenarians, Immunogenetics, Immune Response, Inflammation, Longevity
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