Immune cells regulate body weight

LMU and Harvard researchers show which molecular processes promote secondary diseases in obesity

• A new study by LMU researchers investigates the effects of a high-caloric diet on the immune system.

• After only three weeks, pathological changes of immune status and metabolism arise.

• Immune cells accumulate in adipose tissue, where they form tertiary lymphoid structures; inflammatory markers increase and the metabolism becomes unbalanced.

Munich, March 2022 – Obesity and overweight are among the biggest health challenges of the 21st century, according to the World Health Organization (WHO). Almost 60 percent of Germans are considered overweight, while 25 percent are obese. Moreover, being overweight often triggers severe secondary diseases such as diabetes, arteriosclerosis, or heart attacks.

Immunological processes determine the course of this disease. As part of a new study, a group of LMU researchers led by Dr. Susanne Stutte and Professor Barbara Walzog has shown that a high-caloric diet, even for a period of only three weeks, has drastic effects on the immune system.

“A particular kind of immune cells known as plasmacytoid dendritic cells (pDCs) begins to accumulate in the visceral adipose tissue,” explains Stutte. This adipose tissue is located inside the abdomen and surrounds internal organs. With high caloric diet, small clusters of immune cells form tertiary lymphoid structures inside this fat, resulting in fatal immune responses.

“Now, these pDCs in visceral fat are in a constant state of alarm and release type-I interferon,” explains Walzog. This interferon usually mediates the control of infections, but here it triggers the metabolic syndrome: the metabolism derails and inflammatory markers rise. When the migration of pDCs into the fat is blocked, weight gain is reduced and the metabolic condition improves considerably.

The results of this study, which was carried out in collaboration with Harvard Medical School in Boston, could now contribute to the development of new approaches toward a therapeutic intervention of the metabolic syndrome.