The guardian immune cells, called Adipose Type One Innate Lymphoid
Cells, or ILCs, live in our fat, and are charged with maintaining a
delicate balance of our immune systems.
Scientists have uncovered the physiological mechanics underlying
inflammation and obesity by tracking the actions of 'guardian immune
cells' in response to changes in diet. They believe their work may
herald a new era of research now that they have new therapeutic targets
to prevent and control obesity-related inflammation and metabolic
‘Special guardian immune cells are unable to function properly once obesity is established, which results in severe inflammation and metabolic dysfunction.’
The scientists, led by Professor Lydia Lynch of Trinity College
Dublin and Harvard Medical School, discovered that special guardian
immune cells are unable to function properly once obesity is
established, which results in severe inflammation and metabolic
Professor Lynch said: "All people have fat, even if they are not
obese. Fat is found around almost all tissues in our body, and all fat
has its own immune system, which we are only recently learning about."
"We have revealed that ILCs keep other immune cells called
macrophages in check, by killing them based on certain physiological
conditions in the body - they essentially guard against inflammation
when macrophages are too numerous in fat. This function is unique as
immune cells are not generally supposed to kill other healthy immune
cells in non-pathological conditions."
In other cases, 'natural killer' cells - which are part of the ILC
family - recognize specific proteins on the surfaces of healthy immune
cells that act a little like passwords; if a cell possesses the
password, the natural killer cells let it go about its normal business.
Natural killer cells typically kill cancer cells, which lack the
required password, whereas the healthy immune cells don't.
However, uniquely in fat, the ILCs do not recognize these passwords and instead attack the healthy macrophages.
Professor Lynch said: "We know that macrophages enter fat at the
onset of obesity and that they likely do a protective job cleaning up as
much excess fat as they can. However, as obesity progresses, these
macrophages get overwhelmed by the workload and turn inflammatory, which
leads to more severe obesity and further complications like diabetes."
"Importantly, in healthy states, our ILCs protect against this
inflammation and metabolic disease by killing the troublesome
macrophages in our fat. But when obesity is established these ILCs are
depleted and lose their regulatory killing function, which results in a
dangerous accumulation of macrophages and all the bad things that come
Professor Lynch's work was recently published in the international journal Immunity
The findings confirmed that ILCs are very responsive to diet, which
underlines the role that healthy eating plays in affecting our immune
systems. For example, after eating a fatty diet for just five days, ILCs
home in on fat cells; likewise, their numbers in blood and fat go the
other way when weight is lost.