Elevated levels of "exhausted" white blood cells show how social experiences and stress may shape immune health
People who commonly experience everyday discrimination are more likely to have higher levels of "exhausted" white blood cells, suggesting that the chronic stress of discrimination may hamper the immune system, according to a new study by NYU School of Global Public Health researchers.
"Our findings suggest that everyday experiences of social disadvantage leave physiological traces that accumulate over time," said Emiko Kranz, a PhD student at NYU School of Global Public Health and the first author of the study, published in the journal Brain, Behavior, & Immunity - Health.
Stress is known to alter the immune system, with chronic exposure to stress weakening its defenses. A growing body of research shows that the chronic stress of interpersonal discrimination-through subtle slights, disrespect, or being excluded-is linked to poor health outcomes. While the biology driving these outcomes is not fully understood, scientists hypothesize that discrimination repeatedly activates the body's stress responses, resulting in "weathering" or the gradual deterioration of health.
Previous studies have focused on the links between discrimination and inflammation, reflected in biomarkers such as C-reactive protein, but less is known about the interplay of discrimination and the adaptive immune system, which involves infection-fighting white blood cells such as T and B cells.
"There's a lot of research looking at the role of discrimination in different inflammation-related outcomes, but we wanted to look at the physical response in people's immune systems and how discriminatory stress may impact how immune cell populations function," said Kranz.
The researchers examined surveys and blood samples from 6,337 adults collected as part of the Health and Retirement Study, a longitudinal study of the health patterns of US adults ages 50 and older. In the blood samples, they looked at biomarkers of immune system biology, including levels and functioning of T cells and B cells.
In surveys, the older adults were asked about their experiences with "everyday discrimination," or routine instances of unfair treatment in daily life, which could occur in response to their economic status, race, gender, or other social identities. For instance, people answered questions about whether they are treated with less respect or as if they are not smart, or receive worse service at restaurants or in medical settings.
The researchers found that experiencing higher levels of everyday discrimination was significantly associated with elevated counts of certain T cells (CD4+ TEMRA and CD8+ TEMRA) and B cells (IgD− memory) compared to experiencing average levels of discrimination. Notably, these elevated cell counts were only found in "terminally differentiated" cells-those that transition into an exhausted state from being repeatedly activated-but not "naïve" T or B cells. Terminally differentiated cells have diminished functionality and impaired capacity to mount robust immune responses.
"We weren't only looking at whether there were more or less of the B cells and T cells; we were also able to see what period of their life cycle and level of functionality they had based on whether they were naïve or terminally differentiated cells, which gave us additional insight," noted Kranz.
The authors caution that this study is a starting point for understanding the connection between discrimination and immune system function, and that more research is needed. But overall, their results suggest that social experiences like discrimination may shape immune health at the cellular level and contribute to biological aging by promoting the accumulation of "exhausted," less functional T and B cells.
"This study builds upon well-established research linking experiences of discrimination to systemic inflammation, revealing yet another way that psychosocial stressors become embodied and may contribute to age-related disease processes," said Adolfo Cuevas, associate professor of social and behavioral sciences at NYU School of Global Public Health and the study's senior author.
Additional authors include Jemar Bather, Xiaoyan Zhang, and Virginia Chang of NYU School of Global Public Health, and Steven Cole of UCLA. The research was supported by the National Institute of Diabetes and Digestive and Kidney Diseases (R01DK137246, R01DK137805).
