The white adipose tissue is a hub for memory T cells and promotes memory responses

The white adipose tissue represents 15% of healthy mammalian hosts and bridges body organs. In addition to serving as a scaffold for the lymphatic and blood vasculature, this compartment plays a fundamental role in the control of host metabolism. To which extent the adipose tissue also contributes to immune surveillance and long-term protective defense remains largely unknown. Here, we show that under steady state conditions, the white adipose tissue is home to abundant and diverse memory lymphocyte populations. Following infection, the adipose tissue accumulates large numbers of pathogen-specific memory T cells, including tissue-resident (TRM) cells. Memory T cells found in the adipose tissue express a distinct metabolic profile and are characterized by heightened proliferative and effector capacity. As such, adipose tissue from previously infected mice is sufficient to protect from lethal challenge. Local reactivation of adipose tissue memory T cells leads to rapid responses with local impacts on both immune and metabolic pathways, including direct responses by adipocytes. Notably, induction of recall responses within the adipose tissue is associated with the collapse of lipid metabolism in favor of antimicrobial responses. Thus, our results propose that the white adipose tissue, a compartment that interfaces with all body organs, may represent a unique immune compartment, able to provide early warning and potent effector memory responses. Together, these results uncover the adipose tissue as a dominant reservoir of memory T cells endowed with long-term protective functions, positioning this compartment as a potential major contributor of immunological memory.

16