The Heme Oxygenase System in Immunity

Heme oxygenase (HO) is the rate limiting enzyme in the catabolism of heme with the resultant production of ferrous iron, the bile pigment biliverdin which is subsequently converted to bilirubin by the enzyme biliverdin reductase, and the gas carbon monoxide. The significance of HO has traditionally been associated with the removal of heme, which while a fundamental prosthetic group for hemoproteins, in excess free form can result in cell and tissue damage via the generation of reactive oxygen species. In of itself this would place HO as a central protective enzyme in physiology. However, over the past 30 years researchers have begun to expand on our understanding of the cellular roles that heme and HO products participate in. Many of the cellular functions which the HO-system impacts on appear to be particularly important in how the body/tissue/cells responds to noxious insults, be it infectious, environmental, trauma or neoplastic, and the subsequent immune response. Therefore, the HO-system is now recognized as a player in immunity, reinforcing efforts in developing novel therapeutic agents to target this pathway.

In the field of immunology, the HO-system has been implicated in the regulations of cells of innate and adaptive immune system, the biological response to microbial and parasitic infection, tumor immunity and transplantation, acute and chronic inflammatory diseases and neuroinflammation. The HO-system as also attracted attention as a possible therapeutic target by which to treat various pathologies be they infectious, inflammatory or neoplastic in nature. The goal of this research topic is to bring these different strands of HO-system research together in an attempt to allow a cross fertilization of ideas and best practice, and encourage researchers to construct a coherent and comprehensive narrative for the role of the HO system in immunity.

In this Research Topic, the Topic Editors would welcome reviews or original articles investigating the HO-system; or its components, heme, iron, biliverdin/bilirubin or carbon monoxide, in the modulation of immunity. This includes the regulation, expression and/or functionality of the HO-system in the following areas:

• Molecular and cellular pathways which regulate immunity and the inflammatory response.
• The functional and metabolic regulation of immune cells, including specialized populations of cells e.g. microglial cells.
• The immune and inflammatory response to microbial and parasitic infection.
• The adaptation of tissue, including tissue tolerance, to damage caused by the immune response and inflammation.
• Acute and chronic inflammatory diseases, including but not limited to, autoimmune, autoinflammatory, systemic and neuroinflammatory pathologies.
• Tumor surveillance and immunity.
• The development of new therapeutics for diseases where the immune system and/or inflammatory response contributes to the pathogenesis of the disease.