To identify molecular mechanisms by which early life social conditions might influence adult risk of disease in rhesus macaques (Macaca mulatta), we analyze changes in basal leukocyte gene expression profiles in 4-mo-old animals reared under adverse social conditions. Compared with the basal condition of maternal rearing (MR), leukocytes from peer-reared (PR) animals and PR animals provided with an inanimate surrogate mother (surrogate/peer reared, SPR) show enhanced expression of genes involved in inflammation, cytokine signaling, and T-lymphocyte activation, and suppression of genes involved in several innate antimicrobial defenses including type I interferon (IFN) antiviral responses. Promoter-based bioinformatic analyses implicate increased activity of CREB and NF-κB transcription factors and decreased activity of IFN response factors (IRFs) in structuring the observed differences in gene expression. Transcript origin analyses identify monocytes and CD4+ T lymphocytes as primary cellular mediators of transcriptional up-regulation and B lymphocytes as major sources of down-regulated genes. These findings show that adverse social conditions can become embedded within the basal transcriptome of primate immune cells within the first 4 mo of life, and they implicate sympathetic nervous system-linked transcription control pathways as candidate mediators of those effects and potential targets for health-protective intervention.stress | social genomics | gene regulation E xposure to adverse social environments during early life is associated with increased risk of disease in adulthood (1-5), but the biological mechanisms producing such effects remain poorly understood. One possible explanation suggests that neural and endocrine responses to adversity in childhood affect the development of health-relevant molecular systems (i.e., a "defensive programming" of the developing body) (4, 6-10), rendering the body more vulnerable to subsequent pathogen challenges in adulthood (11,12). Given the transience of most neuroendocrine responses, however, it remains unclear how the extraorganismic social conditions that do "get into the body" during early life could "stay there" over decades to impact the risk of disease in adulthood (13).One molecular mechanism that could potentially create a persisting biological impact of early life socio-environmental conditions involves the complex systems behavior of the gene transcriptional networks that govern cell growth, differentiation, and function (14, 15). Gene regulatory networks show dynamic landscapes in which the system's responses to external perturbations converge on a small number of stable "attractor" modes that can subsequently self-perpetuate (16). These self-perpetuating dynamics are sustained in part by the fact that the mRNA "output" of the system at one point in time (i.e., the genome-wide transcriptional profile) constitutes an "input" to the system at subsequent time points because translated mRNA shapes the cell's response to future environments (17). Mathematical mo...