Hematological consequences of environmental change during dewilding of rhesus macaques

The environment shapes immune system development and the regulation of inflammatory responses, however the hematological consequences of a major environmental change, such as those experienced during migration, remain poorly understood. Here, we assess the immunological consequences in male rhesus macaques as they transitioned from an outdoor provisioned environment to an indoor laboratory facility in a process we term 'dewilding.' Dewilding decreased neutrophils and increased lymphocytes, skewing toward a T_H1 response and increased T cell activation. In the gut microbiome, fungal abundance decreased while bacterial abundance increased. In the bone marrow, we observed a shift towards the less committed multipotent progenitor cells and increased erythrocyte progenitors, with upregulation of genes involved in hemoglobin control and erythropoiesis. Together, our findings illustrate how dewilding alters immune homeostasis, with implications for understanding immune adaptation in migrants from rural to urban environments and for optimizing immunization strategies during environmental change.