Winter is coming, which for millions of people means months of increased exposure to colds, flus and other infectious illnesses. Many people take precautions to ensure that they do not fall ill from these everyday germs, including hand washing and taking extra vitamin C. As we’ve gained more knowledge about sleep and the immune system, many also try to get a proper amount of rest when those around them are coughing and sneezing. Although sleep is definitely an important part of fighting illness, new evidence suggests that your body clock controls immune system function in other ways.

How We Fight Off Illness

Our immune systems are complex and involve many different components working together. However, much of the protection against viruses and even cancer is performed by a type of immune cell called a T cell. T cells are created in our bone marrow and then develop into virus-killing machines in the thymus gland.

In the thymus gland, T cells develop into one of several different types. One of these is the CD-8+ T cell, also known as a killer cell. These cells are particularly toxic to viruses. They recognize viruses in our bloodstreams, and even in our cells, that are attempting to infect our bodies. These cells aggressively attack any intruder, which is why they are so effective. However, their development does not happen randomly. It requires a complex set of steps, all controlled by various genes.

According to new research, these genes may have a circadian rhythm that affects how well we fight off illness at different times of the day.

Internal Clocks, Internal Rhythms

From our body temperature to our appetite, our internal clocks, or circadian rhythms, control most of our bodily functions. Our eyes perceive light and pass messages to our brains, which then release hormones that cue cells throughout our bodies as to the time of day.

Recent evidence suggests that our immune systems also have an innate circadian rhythm. People are more likely to become ill when their circadian rhythm is dysregulated, such as when they are not sleeping enough or when they work nights and other odd shifts. In addition, researchers have long noted that our immune systems do not work equally well at all times of the day, suggesting that there exists a natural rhythm even beyond the healing powers of sleep.

How the Body Clock Controls Immune System

To examine the relationship between immunity and the circadian rhythm, researchers compared two groups of mice. The first group had certain circadian genes deactivated while the second group was composed of completely normal mice. Both groups of mice were given a vaccine to trigger their immune systems.

The second group, all typical mice, showed varied responses according to what time of day they received the vaccination. The mice with their circadian genes deactivated exhibited irregular immune response throughout the day. This circadian timing was especially noticeable when researchers looked at the activation of CD8+ T cells.

This finding has huge ramifications for our health. This type of T cell is our first line of defense not just against colds and the flu, but against cancer. When our circadian rhythms are “on time,” we can expect to have fluctuations in our immune system throughout the day. When they are irregular, we have unpredictable and irregular protection, leaving us more vulnerable to both viruses and cancer.

Raising Your Defenses

How can we apply this new knowledge to our lives? First, getting enough sleep and keeping our circadian rhythms regulated is essential to our health, particularly when it comes to fighting off viruses and different kinds of cancer. Second, there may be advantages to avoiding germ-laden situations until the times of day when your circadian rhythm is the strongest. Because this research was performed on mice, we do not yet know the times during which the human immune system is functioning at its best.

Last, there may be advantages to getting vaccinated at certain times of the day. Although this issue will require more study, it is clear that our immune systems have their own internal clocks which can affect our vaccine response.

Staying Healthy This Cold and Flu Season

Regardless of the time of day, there are a few things you can do to reduce your risk of catching an infectious illness. Make sure your vaccinations are up to date and consider an annual flu shot. Wash your hands and carry hand sanitizer, as most germs are spread through direct contact. Avoid sick people and try to stay home when you are sick as well. Although there is no way to guarantee a year free of sick days, you can increase your chances of remaining in good health until spring arrives once again.