It is well known that this country is in the midst of an obesity epidemic. No matter how long we exercise or how healthy we try to eat, it just does not seem to be enough, as there also seem to be other causes of obesity, including genetics. Some people even consider it an autoimmune, inflammatory disorder, because fat cells may produce various inflammatory molecules that can disrupt the balance established by a normal immune system. Considering this, is there a way to manipulate the immune system in order to battle obesity?

In a study published in Immunity, researchers, led by Yair Reisner from the Weizmann Institute of Science in Israel, sought to do just that. The team studied the immune system processes that trigger metabolic control of fat tissue and found mice that did not have a particular type of immune cell progressively gained excess weight and developed metabolic syndrome even when they consumed a standard diet. Specifically, these mice lacked certain dendritic immune cells — antigen-presenting cells — that release a toxic molecule called perforin.

The mice also showed signs of altered T cells living in their fat tissue, and while T cells normally help fight pathogens, they sometimes cause an autoimmune response. It was only when these T cells were depleted in the mice without the perforin-emitting dendritic cells that their weight gain, and subsequent development of metabolic abnormalities, stopped. "Notably, mice lacking these regulatory dendritic cells were also found to be more prone to develop another form of autoimmunity with symptoms similar to those found in multiple sclerosis," Reisner said in a press release.

Taken together, the observations suggested to Reisner that one of the functions of the perforin-emitting dendritic cells was to remove potentially autoimmune T cells, which would decrease inflammation. According to Reisner, this is the first time researchers have been able to show a connection between fat cells and inflammation in animals that are on a regular diet.

The findings also indicate that these dendritic cells are a key component to protecting against metabolic syndrome and autoimmunity. Moving these cells within close proximity to other immune cell populations may help with the treatment and prevention of those diseases.

"It is hard to predict how this might impact patient care, but we should initially try to find if the absence of this rare subpopulation of cells is associated with obesity, metabolic syndrome, or any autoimmune or other immune abnormalities," Reisner said.

Source: Resiner, Y, et al. Perforin-Positive Dendritic Cells Exhibit an Immuno-regulatory Role in Metabolic Syndrome and Autoimmunity. Immunity. 2015.