Falling in love is associated with immune system gene regulation.

Although falling in love is one of the most important and psychologically potent events in human life, the somatic implications of new romantic love remain poorly understood. Psychological, immunological, and reproductive perspectives offer competing predictions of the specific transcriptional regulatory shifts that might accompany the experience of falling in love. To characterize the impact of romantic love on human genome function, we conducted genome-wide transcriptome profiling of 115 circulating immune cell samples collected from 47 young women over the course of a 2-year longitudinal study. Analyses revealed a selective alteration in immune cell gene regulation characterized by up-regulation of Type I interferon response genes associated with CD1C+/BDCA-1+ dendritic cells (DCs) and CLEC4C+/BDCA-2+ DCs, and a reciprocal down-regulation of α-defensin-related transcripts associated with neutrophil granulocytes. These effects emerged above and beyond the effects of changes in illness, perceived social isolation, and sexual contact. These findings are consistent with a selective up-regulation of innate immune responses to viral infections (e.g., Type I interferons and DC) and with DC facilitation of sexual reproduction, and provide insight into the immunoregulatory correlates of one of the keystone experiences in human life.