The immune system in animals is fortified as a precaution in times of energy shortage by a hunger- or stress-induced mechanism that releases antimicrobial peptides.
"Bonn researchers have discovered an elementary mechanism which regulates vital immune functions in healthy people. In situations of hunger which mean stress for the body's cells, the body releases more antimicrobial peptides in order to protect itself.
"…The biomedical researchers from the LIMES Institute at the University of Bonn have been able to show in fruit flies but also in human tissue that this natural immune defence system is linked directly to the metabolic status via the insulin signalling pathway.
"If we have not eaten for a while or have to climb many stairs, the energy level of our cells drops and with it the level of insulin. The researchers from Bonn have now discovered that in the case of a low insulin level the FOXO transcription factor is activated. A transcription factor can switch genes on and off. FOXO switches genes for immune defence proteins on when energy is needed. These antimicrobial peptides (AMP) -- not to be confused with antibodies -- are subsequently jettisoned by the body's cells. They destroy possible pathogens by dissolving their cell walls.
"…In situations of hunger which mean stress for the body cells, the body releases antimicrobial peptides as a precaution in order to protect itself." (Science Daily 2010)
Learn more about this functional adaptation.