Tissue‐resident memory CD8+ T cells (TRM) localize to barrier tissues and mediate local protection against reinvading pathogens. Circulating central memory (TCM) and effector memory CD8+ T cells (TEM) also contribute to tissue recall responses, but their potential to form mucosal TRM remains unclear. Here, we employed adoptive transfer and lymphocytic choriomeningitis virus reinfection models to specifically assess secondary responses of TCM and TEM at mucosal sites. Donor TCM and TEM exhibited robust systemic recall responses, but only limited accumulation in the small intestine, consistent with reduced expression of tissue‐homing and ‐retention molecules. Murine and human circulating memory T cells also exhibited limited CD103 upregulation following TGF‐β stimulation. Upon pathogen clearance, TCM and TEM readily gave rise to secondary TEM. TCM also formed secondary central memory in lymphoid tissues and TRM in internal tissues, for example, the liver. Both TCM and TEM failed to substantially contribute to resident mucosal memory in the small intestine, while activated intestinal TRM, but not liver TRM, efficiently reformed CD103+ TRM. Our findings demonstrate that circulating TCM and TEM are limited in generating mucosal TRM upon reinfection. This may pose important implications on cell therapy and vaccination strategies employing memory CD8+ T cells for protection at mucosal sites.

Diabetes mellitus type 2 (T2D) causes an increased risk of morbidity and mortality in response to viral infection. T2D is characterized by hyperglycemia and is typically associated with insulin resistance and compensatory hyperinsulinemia. CD8 T cells express the insulin receptor and previously we have shown that insulin is able to directly modulate effector CD8 T cell function. We therefore hypothesized memory CD8 T cell responsiveness in context of T2D is negatively impacted by hyperinsulinemia or hyperglycemia. Using a mouse model for T2D we could show that memory CD8 T cell function was significantly reduced in response to re-challenge by viral infection or with melanoma cells. Basal insulin injection of mice increased GLUT-1 expression and glucose uptake in memory CD8 T cell precursors early after infection, which was prevented when these cells were deficient for the insulin receptor. However, neither insulin injection, nor insulin receptor deficiency resulted in a difference in metabolism, memory formation, cytokine production or recall responses of memory CD8 T cells compared to controls. Importantly, in context of obesity, insulin receptor deficiency on CD8 T cells did not affect the functional capacity of memory CD8 T cells. In contrast, we could show in vitro and in vivo that hyperglycemia significantly impairs the antiviral capacity of memory CD8 T cells. Our findings indicate that obesity impairs the memory CD8 T cell response against viral infection and cancer through the detrimental effects of hyperglycemia rather than hyperinsulinemia.