One of the first studies to analyze the relationship between social factors and human gene expression surveyed transcriptional profiles in white blood cells (leukocytes) from healthy older adults who differed in the extent to which they felt socially connected to others (Cole et al., 2007). Among the 22,283 genes assayed, 209 showed systematically different levels of expression in people who reported feeling lonely and distant from others consistently over the course of 4 years (Figure 2). These effects did not involve a random smattering of all human genes, but focally impacted three specific groups of genes. Genes supporting the early “accelerator” phase of the immune response – inflammation – were selectively up-regulated. However, two groups of genes involved in the subsequent “steering” of immune responses were down-regulated: genes involved in responses to viral infections (particularly Type I interferons), and genes involved in the production of antibodies by B lymphocytes. These results provided a molecular framework for understanding why socially isolated individuals show heightened vulnerability to inflammation-driven cardiovascular diseases (i.e., excessive non-specific immune activity) and impaired responses to viral infections and
