There has been some evidence in the scientific literature
that adipocytes – cells whose specialized function is the storage of fat – play
an immunological role. Since microbial infection
immediately results in the rapid growth of the infectious agent, it is essential
that the host tissue mount an immediate immunological defense. Part of this innate defense involves the
mobilization of host cells from the local environment such as epidermal cells,
mast cells and locally resident leukocytes – white cells found in the
peripheral blood circulation. This line
of defense is especially important during the lag phase before the recruitment
of neutrophils and monocytes. The production
of antimicrobial peptides (AMPs) by locally available cells and leukocytes is critical
during the initial stage of infection.
In an effort to further elucidate the mechanism of early
immunological responses to infection, Dr. Ling-Juan Zhang and fellow
researchers from the Division of Dermatology at the University of California in
San Diego, examined in detail the initial stages of infection by Staphylococcus
aureus - a microorganism responsible for serious skin and soft tissue
infections that often results in systemic as well as local disease. From these studies, they discovered some
interesting findings.
What these investigators discovered, using the mouse animal
model, was that increased cellular expansion of the subcutaneous adipose layer
consisting of adipocytes accompanied infection with Staphylococcus aureus. Furthermore, these adipocytes were
responsible for the production of a potent AMP referred to as
cathelicidin. As further evidence that
adipocytes had an immunological role in defending against infection, mice that
possessed adipocytes that lacked the ability to produce cathelicidin were
unable to inhibit bacterial infection.
Finally, it was also demonstrated that human adipocytes also were
responsible for the production of cathelicidin.
Clarifying the role of adipocytes in the initial immunological
response to infection is of great interest.
A full understanding of this mechanism may prove to be of immense therapeutic
value in the treatment of infection by Staphylococcus aureus.