Memory T Cells Shelter in Bone Marrow, Boosting Immunity
in Mice with Restricted Diets

Dietary restriction promotes memory T cell accumulation
in BM

BM trophic factors and adipocytes promote memory T cell
accumulation in BM

Memory T cells display enhanced protective function
during dietary restriction

September 07, 2019 : Even when taking in fewer calories and
nutrients, humans and other mammals usually remain protected against infectious
diseases they have already encountered. This may be because memory T
cells, which are located throughout the body and required to maintain immune
responses to infectious agents, retreat to the bone marrow
during dietary restriction according to scientists at the National
Institute of Allergy and Infectious Diseases (NIAID), part of the
National Institutes of Health (USA). Their study in mice (The Bone Marrow
Protects and Optimizes Immunological Memory during Dietary Restriction),
published online in Cell,
also found that animals undergoing dietary restriction were better protected
against tumors and bacterial infections than animals with
unrestricted diets.

Researchers led by Yasmine Belkaid, Ph.D., chief of
the Metaorganism Immunity Section in NIAID’s Division of Intramural Research,
previously observed that fat tissue harbors memory T cells in
mice. They investigated whether this phenomenon helped preserve immune memory
when calorie intake was reduced. To investigate, they restricted the diet of
mice previously given full access to food. While receiving less food, mice had
fewer memory T cells in their lymphoid tissues, where they normally linger, and
more of the T cells in bone marrow that became enriched with fat tissue.

Investigators then evaluated how well memory T cells
performed when mice ate less. While eating freely, mice were infected with the bacterium
Yersinia pseudotuberculosis. After the mice developed immunological
memory, researchers restricted the diets of some of the mice for up to four
weeks before again exposing all the mice to Y. pseudotuberculosis. Mice with
restricted diets had more robust memory T cell responses and were better
protected from illness. The researchers repeated this experiment using a vaccine
that trains immune cells to fight melanomas and found that memory T cells were
more protective against tumors in mice receiving less food.

Though this phenomenon has yet to be studied in humans, the
findings suggest how the immune system may have evolved to help mammals survive
periods of limited food availability while keeping their immunity intact. These
results in lab animals cannot be extrapolated to dietary advice for people.
However, these insights may one day help clinicians improve immunotherapy for
cancers and other diseases by optimizing nutrition.

Indian-origin scientist Dhawal Dixit was also involved in the research team.

Dhawal Dixit is affiliated with Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016, USA.

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