Most biologists and keen medics know that the main immunological response in the body consists of a series of processes carried out by white blood cells in the production of antitoxins and antibodies. When a foreign antigen is recognised by the body’s defence system, it stimulates Macrophages which engulf then display the antigen on their surface. Helper T-cells then prompt B-cells into the production of plasma cells which secrete antibodies specifically complementary to the foreign antigen. T- cytotoxic cells are also stimulated to give rise to more of the same cells as well as immunological memory cells. These cells mean that the next time the same antigen is recognised by the body’s defence system, the response will be more immediate.
At Linköping University in Sweden, researchers are investigating the effect of another possible addition which aids the immunological system in the body. This is in the form of a warning system by mitochondria.
Mitochondria usually act as a production of energy for body cells by respiration.They burn sugars and lipids to form water and carbon dioxide as well as energy in the form of ATP (adenine triphosphate releases energy when it breaks down into ADP- adenine diphosphate and an inorganic phosphate molecule).
It has been discovered there are DNA fibres that are secreted by the mitochondria of white blood cells. These are then released as a ‘web’ of mtDNA (mitochondrial DNA) which raises an alarm to the body’s immune system that the body has been exposed to a foreign antigen and is under attack. It also causes other white blood cells to release a signal called “interferon type 1” which is a substance that helps the immune system to combat an infection.
From previous studies, we know that levels of mt DNA can be increased after the introduction of particular inflammatory diseases (e.g. rheumatoid arthritis, atherosclerosis, and hay fever) as well as after surgical trauma. I.e. mtDNA is one of the primary explanations for inflammation.
“…we will try to reduce the release of mtDNA, and in this way reduce the inflammation that it causes,” explains Björn Ingelsson, researcher and associate lecturer at the Department of Clinical and Experimental Medicine at Linköping University. He has conducted the research together with Professor Emeritus Anders Rosén and other co-workers.
There are a few ways in which mtDNA webs differ from other webs which makes it so fundamentaklt imprtant.
mtDNA is activated at a mucg faster rate, of a few minutes, than other webs (e.g neutrophil-based meshes).
mtDNA also has its characteristica ‘signal/warning’ function that others do not.
mtDNA webs survive in the blood longer before being dissolved.
Significantly, it mustr be stated that mtDNA webs are a critical positive contribution to the body’s defense however:
“you can have too much of a good thing. If an unintentional secretion of mtDNA occurs, or if the secreted mtDNA is not removed from the blood, undesired inflammation may occur, and it is this side-effect we want to prevent,” says Björn Ingelsson.
High levels of interferon type 1, the signal substance activated by the mtDNA webs, occur in several autoimmune diseases and several types of cancer. Researchers hope to quantify the secreted mtDNA molecules and to understand the warning signals, and therefore diseases including several autoimmune diseases and even cancer.