Natural immunostimulants and immunosenescence : Anti-aging strategies

17 - 01 - 2022

Advancing age is accompanied by a progressive declineofthe immune system called immunosenescence– anevolutionary processaffecting immune and vaccine responses (dysimmunity) and, consequently,the incidence of pathologies (e.g., infections, autoimmune reactions, chronic inflammation, degenerative processes, cancers, etc.) commonly associated with age.

Although age is the major contributing factor, it is not the only cause of immunosenescence, so that it should rather be seen as a consequence of events or morbid conditions, such as thymic involution from puberty, latent infections, nutritional deficiencies, metabolic or hormonal dysregulations, stress, sleep disorders, addictions (alcohol, smoking, etc.), etc. This results in a great heterogeneity of manifestations between people of a given age, raising questions about the influence of immunosenescence in the physiological ageing process.

Non-optimal nutritional status, and more particularly micronutritional deficiencies, such as a lack of essential fatty acids (e.g., omegas-3), deficiencies in amino acids (e.g., arginine, glutamine), vitamins (e.g., A, B6, B9, B12, C, D, and E) and minerals (e.g., zinc, selenium, iron, copper), are sources of immunodeficiencies and immune deregulation. A healthy lifestyle and a varied and balanced diet rich in antioxidant micronutrients are therefore necessary.

Immunosenescence is characterised by quantitative and functional changes in immune cells and their responses. Hematopoietic stem cells, known for their self-renewaland totipotency (the potential to differentiate into all the figurative elements of the blood), graduallylose their functionality, both in terms of renewal and differentiation. This results in a reduction of certain cell populations (e.g. antigen-presenting cells/phagocytes, circulating pools of naive B and T cells, etc.) affecting both innate and acquired or adaptive immunity, as evidenced by the paucity of antigenic responses observed. Attributable to oxidative stress, these functional alterations can be restored by antioxidant treatments. Apositive impact on lymphocyte proliferation and infectious susceptibility in the elderly has been noted with zinc, selenium and vitamin E supplementation..

Natural extracts are of great interest in this respect. Prescribed in traditional Chinese medicine as an immunostimulant tonic, the root of astragalus( Astragalus membranaceus) is, due to its antioxidant and senolytic properties, particularly indicated for the support of the immune systemof elderly or weakened subjects. Other plants, such as rhodiola( Rhodiola rosea) and echinacea (Echinacea purpurea), are also indicated. The same applies to extracts of reishi ( Ganoderma lucidum), a medicinal mushroom from the Chinese pharmacopoeia known for itsproactive effects onthe immune system and immunosenescence.

Significant research efforts are currently being made to delayorreverse the effects of immunosenescence. Possible interventions can be divided into three types of strategies: (i) so-called restoration strategies consisting of administering factors (e.g., cytokines, hormones, micronutrients, extracts, etc.) known to have favourable effects, (ii) so-called replacement strategies consisting of eliminating senescent immune cells, while stimulating their replacement by immunocompetent cells, and, finally, (iii) so-called replacement strategies consisting of eliminating senescent immune cells, while stimulating their replacement by immunocompetent cells, and, finally, (iii) These approaches offer real prospects.