The metabolism revolution: you need energy to fight and to live

In times when only single-cell organisms populated the earth, some evolved to use energy from oxygen. Then, one of these aerobic bacteria formed an endosymbiotic alliance with larger anaerobic bacteria. The smaller cell continued to use oxygen as a source of energy but continued to do so from the safety of a new home. As a means to pay rent, it started to share its energy with the host. In evolutionary terms, this deal offered the platform to dominate other forms of simple organisms, eventually forming eukaryotic cells as we know them today. The small ingested cell became the mitochondrion, increasing mutual dependence with the bigger cell, but retaining its main task of harnessing energy from oxygen consumption. This helped to build other specialized organelles within the bigger cell in time leading to multicellular organisms, including human beings. This deal made a long time ago determined the world as we know it and is responsible for all of the diversity around us. In this book, while we will not cover topics as broad as the foundation and evolution of our species, we will focus specifically on how regulation of cellular energy affects immune cell functions, enabling host defense during infection or injury. Employing multiple examples, we will illustrate how studying cellular energy of the immune system can be exploited to fight diseases.