A Weak Immune Defence

The aging of the immune system has profound consequences. Since there is an early and complete involution of the thymus the population of naive T-cells decreases whereas the number of memory T-cells increases. From middle age on effector T-cells start to dominate the T-cell population. Effector T-cells have proinflammatory properties and inhibit the production of antibodies. This chronic inflammation promotes the development and progress of age-associated diseases like Alzheimer's disease, atherosclerosis, and osteoporosis. In addition naive T-cells age and become senescent. Thus, the aging immune system cannot detect new infectious agents sufficiently. Elderly can not rely completely on the protective effects of immunizations and need booster immunizations more frequently.