Diets and healthy eating habits hold promise for preventing and treating diseases, but far less is known about acute effects to the immune system shortly after a meal.

In a study published in Nature, a University of Pittsburgh team found that eating creates a temporary metabolic state that influences the function of T cells –  immune cells that help the body detect and fight infection and disease, including cancer.

In experiments in mice and humans, T cells collected after a meal showed a metabolic and functional advantage over those collected after fasting.

The findings suggest that eating can have a lasting effect on how immune cells respond when they are activated –  a factor that could be relevant for T cell–based immunotherapies, such as CAR‑T cell therapy, as well as for responses to infection.

“We initially expected to see little difference between T cells collected from individuals who had eaten and those who had fasted. Instead, we found the opposite,” said corresponding author of the study Greg Delgoffe, Ph.D., professor of immunology at Pitt and associate director for basic research at UPMC Hillman Cancer Centre.

“What stood out was not just the difference itself, but that it was long-lasting.”

That durability matters because most T cells are not activated immediately after eating.

However, if a T cell encounters a pathogen while this post‑meal metabolic advantage is still present, it responds more strongly, linking a short‑term nutritional state to a later immune response.

To test whether this effect could be seen in people, the team collected blood samples from healthy volunteers before breakfast and again about six hours after they ate.

T cells collected after eating showed metabolic advantages that left them better prepared to respond if an infection occurred later, reflecting high energy demands necessary to launch an immune response.

Follow‑up experiments in mice confirmed that eating creates a temporary opportunity for T cells to obtain nutrients.

Some of those cells retained a functional advantage and responded better if they were activated later, up to seven days afterward.

The effect was driven by fats circulating in the bloodstream after a meal.

These fats, carried in particles called chylomicrons, were sufficient to enhance T cell function, showing that immune cells can directly access and use dietary lipids.

Despite the durability of the effect, the researchers did not find major changes in the T cells at a genetic level.

Instead, the advantage depended on increased protein production, and when that process was blocked, the post‑meal effect disappeared.

“Piecing together the biology behind this effect required a broad collaborative effort at Pitt,” said Delgoffe, who also directs the Tumour Microenvironment Centre at UPMC Hillman Cancer Centre.

“It brought together expertise in nutrition, metabolism and immunology to understand what was really happening inside these cells.”

How eating could be shaping T Cells in cancer therapy

The findings have particular relevance for cancer immunotherapy, including CAR‑T cell therapy.

In this approach, T cells are collected from a patient’s blood, modified in the laboratory to recognise cancer cells and then reinfused into the patient to attack the tumour.

To test whether the metabolic state of T cells at the time of collection could influence this process, the researchers generated CAR‑T cells from human T cells that were collected either after fasting or after eating and tested them in mouse tumour models.

In these preclinical experiments, CAR‑T cells made from post‑meal T cells persisted longer and showed improved tumour control than those made from fasted T cells.

While the findings point to new biological insights, the study does not suggest that eating treats cancer or that patients should change their diets.

Instead, it highlights timing as a critical and previously overlooked variable.

By showing how immune cell performance can vary depending on metabolic state, the work points to new ways researchers might think about when immune cells are collected, activated or analysed.

Additional authors of the study include Alok Kumar, Ph.D., Dayana Rivadeneira, Ph.D., Isha Mehta, Bingxian Xie, Ph.D., Rachel Cumberland, Supriya Joshi, Ph.D., Jitendra Kanshana, Ph.D., William Gunn, Victoria Dean, Angelina Parise, Kristin Morder, Erica Myers, Steven Mullett, Richard Cattley, Stacy Gelhaus, Ph.D., Abigail Overacre-Delgoffe, Ph.D., Jishnu Das, Ph.D., William Hawse, Ph.D., and Alison Kohan, Ph.D. all of Pitt, UPMC or both.

Source: University of Pittsburgh