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.