When we come down with the flu in the midst of winter, or something just doesn’t feel right, most of us pick up the phone and make an appointment with our doctor. However, not all of us can afford a doctor, and those living in poverty or a lower social class often have less access to healthcare.

According to The New York Times, the lower a person is on the social ladder, the higher the risk of illnesses like heart disease, diabetes, cancer and other psychiatric disorders. A 2014 study based on income data reported that people in the top 1 percent had life expectancies that were 10 to 15 years longer than those in the bottom 1 percent.

This difference in lifespans could be due to the stressors those in lower social classes face, such as lack of control over life circumstances, increased engagement in drug use and increased exposure to microbes and toxins.

Researchers have known for a while that low social status is associated with a shorter lifespan, but the exact mechanism of this phenomenon has remained unclear because it’s nearly impossible to move human subjects up and down the social ladder and measure their health, which is why they turned toward female rhesus monkeys.

According to Science Magazine, a team of researchers were able to manipulate the pecking order of the monkeys’ hierarchical society to observe the relationship between dominance rank and immune system efficiency.

The team introduced these captive monkeys into new social groups in which they didn’t know any of the other monkeys. The one introduced first became the alpha, the one introduced second became the beta, and so on.

After three months of living in these new social groups, the researchers drew blood samples from the monkeys to collect immune cells and measure gene expression across their entire genomes. They found that more than 1,600 genes in white blood cells (which fight against infection) were affected by social status.

To verify these changes in the genome were important, the researchers simulated a bacterial infection against the collected immune cells to see if they could still fight off the sickness. According to the researchers, the immune cells from lower-ranking monkeys were less effective at fighting the infection.

“There was nothing intrinsic about these females that made them low status versus high status,” leader of the study and postdoctoral researcher at Duke University Noah Snyder-Mackler told The New York Times. “But how we manipulated their status had pervasive effects on their immune system.”

Lower-ranking monkeys were also subject to harassment and abuse by the higher-ranking members of the group, which increased the activity of inflammatory-related genes. Inflammation is a normal way for the body to fight off disease-causing organisms, but it can become a problem for your own cells when inflammation is constant.

The researchers also noted that higher-class monkeys were more likely to be groomed and comforted by other animals, and those who were more frequently groomed were less likely to show an inflammatory response.

To determine if switching the established pecking order would reverse the bad health effects, the researchers created new groups and changed their ranks by changing the order in which they’re introduced.

They found that gene expression levels in white blood cells changed within the next three months, and immune cells from previously low-ranking monkeys were now better at fighting off infection.

“I like to think there is a positive societal message,” Snyder-Mackler said. “If you take an individual out of their poor social environment, at least in these adults, you’re able to reverse the effects on their immune cell function.”

Assuming the results of the study would be similar in human subjects, it raises the possibility that vulnerability to certain illnesses might shift if people’s social circumstances are changed. Chronic stress, often accompanying lower social status, is associated with chronic inflammation, which is suspected to increase a person’s risk for heart disease and Alzheimer’s.

According to Steve Cole, a UCLA neuroimmunologist not involved in the study, the findings pose questions about how best to help low-status communities.

“It may not be sufficient just to equalize access to healthcare, or protection from microbes and toxins,” Cole said. “What else do we need to do?”

The results of the study open our eyes to the possibility that inequalities in the system are not only damaging to a person’s character but also their biological health. Those living below the poverty line have limited access to healthcare, and they also may be predisposed to chronic inflammation and a lowered immune response.

These types of findings may not give us all the information we need, but they’re a stepping stone in the right direction, so it’s important to keep paying attention to what’s happening in our scientific communities.