GROWTH HORMONE, IMMUNOSENESCENCE AND VACCINATION FAILURE IN THE ELDERLY

In the aging population, the longitudinal decrease in the secretion of steroidal and polypeptides growth hormones is directly associated with accumulation of senescent cells in tissues and organs. The cellular hypo-replicative senescence state is caused by metabolic stress and persistent DNA damage, which lead to the activation of the p16^INK4a cell-cycle inhibitor, retinoblastoma and p53 pathways. Aging increases the susceptibility to physical frailty, sarcopenia, diabetes, atherosclerosis, infectious disease and cancer in the older adults. As a consequence of immunosenescence and reduced immunoreactivity of the innate and adaptive systems, seniors have a weak response to vaccination. The high doses of vaccines have been recommended to boost growth and activation of memory T and B cells in non-responsive older individuals, but it is not sufficient for long-term protection. The treatment with recombinant human growth hormone has been shown to regenerate thymus and increase the repertoire of naive T cells CD4+ and CD8+ T cell and B cell subsets in people with age-related diseases, chronic viral infection and immunodeficiencies. This review presents an update on senescence biology and their clinical immunological manifestations in the elderly. We describe possible immune mechanisms by which personalized recombinant growth hormone therapy could act to prolong the effectiveness of the vaccines recommended to older adults.