The Immune System and Aging

HIV affects each of us differently. Some people progress to symptoms very quickly; others live for 20-plus years without any signs of immune suppression or symptoms. Each of us age differently as well. How we age and how the aging of our bodies impacts our health is unique to each of us. The immune system is greatly affected by aging. Therefore, HIV infection -- coupled with aging -- creates added challenges for maintaining good health.

Our immune system's ability to perform declines with age. These changes happen at all levels, from chemical changes in how our cells communicate with one another to changes in immune organs altogether. A study is currently underway on the effects of HIV, aging and the immune system. However, it will likely be some time before information is available. In the meantime, here's some information to ponder.

The Skin: Skin is the first line of defense against many infections. For many people, visible signs of skin aging begins at about 25 years -- fine lines and wrinkles start to reveal the natural process of the skin breaking down. Then, as women enter menopause, the fatty underlayer of skin thins from hormonal changes. The skin also becomes more vulnerable to cuts and abrasions, and it loses some of its resilience and elasticity.

Most skin conditions associated with aging are relatively harmless and to some degree unavoidable. Others can be painful, itchy or even life-threatening, like cancer. Some include wrinkles, shingles, drying of the skin, skin lesions (from warts to liver spots), dermatitis, varicose veins and leg ulcers. HIV affects the skin as well. Often, skin conditions are among the first signs of immune dysfunction associated with HIV. (Read Project Inform's Skin Conditions or call 1-800-822-7422.)

The Thymus: This organ is located beneath the breastbone and above the heart. When we're born, the thymus is large, nearly covering the whole chest like a bib. The organ is important for developing new T-cells (also called naïve T-cells), including CD4+ and CD8+ cells.

In children this organ is very active, making many new T-cells and building the immune defenses that will help protect us late into our lives. In our early teens, the thymus has done most of its job. We're then generally considered to be immunologically adult. By the time we're in our early twenties, the thymus shrinks in size, becomes fatty and is believed to contribute little to new T-cells for the rest of our lives. Thus, a healthy, HIV-negative 40-year-old is not likely to have much functioning thymus tissue.

One study has shown that peo-ple living with HIV are more likely to have a functioning thymus than HIV-negative people. This might be because the immune system is weakened and the thymus needs to re-grow in response to immune suppression. Even still, a 40-year-old with HIV is less likely to have robust thymus activity compared to a 20-year-old with HIV. Because this organ is so important for new T-cell development, how aging impacts the potential for immune reconstitution in HIV disease might be quite profound.

The New or Naive T-cell: Naïve T-cells are cells that can create an immune response and deal with new infections. Generally speaking, once a naïve T-cell encounters and creates an immune response to an infection, it then becomes a memory T-cell. The elderly have virtually no naïve T-cells. This is for two reasons: (1) over time naïve cells eventually become memory cells, and (2) there is little-to-no functioning thymus left to replenish the body's stores.

As you age, your immune system finds it difficult and sometimes impossible to respond to new infections like a young person would. Your immune system may take much longer to tackle an infection or it may simply not respond at all.

Interleukin-2 (IL-2): As we age, calcium gets depleted from our bodies. Calcium is important for strong bones. It also helps cells produce chemicals called cytokines -- what your immune system uses to communicate. IL-2 is one cytokine that is very important for T-cell reproduction and their long-term growth.

As T-cells age, they lose the ability to function properly and produce IL-2. As a person ages, there are changes in their T-cell function and, as individual cells age, there are changes in those cells' function as well. HIV infection also decreases IL-2 production and T-cell dysfunction is well documented in HIV disease.

Telomere Length: With new technology, scientists can measure a telomere (end of a chromosome) and estimate the replicative history of a cell. In 100-year-old people, the telomere length inside their cells is very short. Some studies show that the telomere length in cells from people with HIV is almost identical to those of a 100-year-old. This suggests that HIV hastens the aging of the immune system.

Other Cells: Aging impacts other cells as well, including B-cells, which are important for making antibodies. Antibodies help battle infections outside of cells. Studies suggest that antibodies in elderly people are limited, not able to deal with a broad range of infections. Auto-antibodies, or antibodies against the "self," have been correlated with aging. They are more prevalent in elderly people and are associated with auto-immune diseases, like arthritis or skin conditions. Increased rates of auto-immune diseases are also associated with HIV infection. Moreover, the development of antibodies in response to vaccinations is markedly reduced in both HIV-positive people and the elderly.

These are just some of the ways of how aging impacts the immune system, and how they might interact with HIV infection. While both aging and HIV can profoundly affect the immune system, the take-home message mustn't be of despair, but rather a red flag to take action and support your immune system so that you can lead a healthy and long life.

In the face of aging and HIV infection, there are many ways to enhance and strengthen your immune system. One way to strengthen your body and its ability to fight disease is to work closely with a healthcare professional to find out what's best for you. Other ways include basic skin care, improving nutrition, getting age-appropriate health screening, promptly treating conditions when they occur and developing comprehensive preventive strategies.

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This document was provided by Project Inform.