As we get older, our immune system changes in a way that can also affect the brain. In people over fifty, the production of new immune cells decreases sharply. As a result, older, less well-functioning cells accumulate in the body. These senescent cells release substances that can be harmful, including to memory.
Researchers discovered that a specific group of immune cells, known as CD8+ T cells, produces a protein in older people that negatively affects memory. This protein, granzyme K, causes disruption in the hippocampus, an important brain region for storing memories. This process plays a role in the decline in cognitive functions often seen in older people.
Normally, barriers in the brain ensure that harmful substances and cells are kept out. As people age, these barriers deteriorate, allowing signals from inflamed immune cells to reach the brain more easily and cause damage there. This insight helps explain why the ageing immune system can affect mental health.
Interestingly, research shows that these harmful effects of the immune cells are reversible. By blocking granzyme K, cognitive decline was inhibited. This opens up new possibilities for treatments that can protect memory in older people.
This discovery highlights the importance of a well-functioning immune system for healthy ageing, including for the brain.
Source: Reason
