White blood cells, such as neutrophils and macrophages, are part of the immune system in people and other mammals and they provide protection from pathogens. An interesting study has revealed that the body’s defense system also includes a rather surprising member: fat.
The research indicates that fat cells increase in number and size around the site of a skin infection. In addition to this, they also produce a special type of antibiotic that has some effect on bacteria transient or residential to human skin (which includes several types of potentially pathogenic bacteria.) Before white blood cells make their way to the site of infection, fat cells in the area are already reacting.
For the study, a research group led by Richard Gallo injected mice with methicillin-resistant Staphylococcus aureus (MRSA). On studying this, they noted that the layer of fat around the injection site grew thicker as a direct result of increased numbers of fat cells (adipocytes.)
The importance of this mechanism was shown by the fact that mice that could not produce new adipocytes were less able to combat MRSA infection than were control animals (which could produce adequate numbers of fat cells.)
On further study, it was found that the infection also triggered the fat cells to produce an antibiotic peptide called cathelicidin. This was previously unknown. The researchers further showed that human adipocytes can make the same antimicrobial compound in vitro, suggesting that similar mechanisms of protection could also be active in people. Further research will need to be performed in order to confirm this.
However, there was a note of warning with the research for more fat does not necessarily mean a better response to infection. So there is no advantage in being overweight. As it stands, the high levels of cathelicidin pumped out by the fat cells could lead to inflammatory diseases such as lupus and psoriasis, and the obese mice the researchers studied were less able to fight MRSA infection than animals of healthy weight.
In summary, the results suggest that a healthy amount of fat seems to be the key to a strong immune system.
The research was undertaken by scientists based at the University of California, San Diego Medical School. The findings have been published in the journal Science. The paper is titled “Dermal adipocytes protect against invasive Staphylococcus aureus skin infection.”
