Body fat immune cells help protect against cold, study finds

New research led by a Trinity College Dublin scientist has found immune cells living within body fat can help protect the body against cold.

The findings, overseen by associate professor in immunology Lydia Lynch, could help in the treatment of obesity and various “wasting” conditions.

The discovery involves special immune or “gd T” cells found to live within fat and which regulate body heat and help protect against “cold shock”.

It has led to a new understanding that as well as protecting against infection, these immune cells also help to regulate metabolism.

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There are two distinct types of fat - white and brown. White fat primarily stores energy from consumed food, the more of which we don’t use, the fatter we get.

On the other hand, brown fat is burned to produce heat, a particularly important function in newborn babies and in protecting against hypothermia.

Gd T cells are normally located at "barrier sites" around the body to combat infection but the study, whose findings are published in the journal Nature Immunology, has located a population of them in fat.

When researchers removed these cells from the fat in mice they found they lost body heat and, in cold environments, died as a result of being unable to regulate their temperature.

"Surprisingly, we found that the immune cells in fat respond to cold temperatures - they play an integral part in regulating thermogenesis by 'turning on' the burning of white fat, or by stimulating the conversion of white fat into brown fat, which generates the heat required to keep us warm in the cold," Professor Lynch said of the research.

“This heat generation happens when the lipids in the white fat are burned up, and, when this occurs, weight loss is the chief side effect.”

The findings could have significant effects on research into the treatment of a number of conditions.

For example, with obesity, activating this biological pathway and “kick-starting the body” into burning white fat may induce weight loss, the researchers believe.

In wasting conditions, often associated with cancer or AIDS, switching off the pathway may induce desirable weight gain.