Nav: Home

Cell 'cannibalism' educates our defenses

May 03, 2017

Phagocytosis is a biological mechanism whereby specialized cells ingest and degrade old, dead, or damaged cells to prevent tissue damage due to their accumulation. But phagocytosis appears to also have an educational role. Scientists at the Centro Nacional de Investigadores Cardiovasculares Carlos III (CNIC) report in the Journal of Experimental Medicine that phagocytosis not only eliminates useless cells, but also 'educates' macrophages, the immune cells that carry it out.

It is a paradox of nature that death is a prerequisite for the continuation of life. This is no more evident than in our own bodies, in which billions of cells in the intestine, the blood, the skin, and other tissues die every day so that new ones can take their place. Scientists have long investigated how organisms eliminate the debris from these expired cells. One of the commonest mechanisms turns out to be that specialized cells eat the old, dead, or damaged cells. This digestive process, called phagocytosis, is carried out by cells called macrophages, a name that means "big eaters".

Macrophages are immune cells that normally are distributed throughout all body tissues and work to rid the organism of any type of biological material that needs to be eliminated, from injurious material such as glass particles and viruses to proteins or larger complexes that appear, for example, during embryonic development. Macrophages are also important for eliminating dangerous cells, for example, cancer cells or lymphocytes that recognize self molecules and that could cause an autoimmune immune disorder, such as those found in patients with lupus of rheumatoid arthritis.

The Journal of Experimental Medicine report is the fruit of a joint effort by teams from the Spanish National Cancer Research Center (CNIO), the Spanish Superior Scientific Research Council (CSIC), and groups from the USA, and was coordinated by Noelia Alonso-González and Andrés Hidalgo of the CNIC Cell Biology and Development Area. In the study, the research team used an ingenious method for joining the circulations of 2 mice, with the cells of one mouse expressing a fluorescent protein. "When macrophages from the non-fluorescent mouse ingest cells from the partner mouse, they acquire their fluorescence," explains Noelia Alonso-González. This simple approach helped the research team to isolate and study phagocytosing macrophages in living tissues for the first time.

The study shows that phagocytosing macrophages are different in each tissue, and different from macrophages that do not ingest dead or damaged cells. These differences, explains Andrés Hidalgo, "are important because they keep inflammatory processes in check and in turn promote the elimination of damaged cells; in other words, they increase their 'appetite'". Previous research had shown that when phagocytosis functions abnormally organisms can develop autoimmune disorders. The new CNIC study shows for the first time how phagocytosis is actually organized in living tissue.

An important conclusion of the study is that the act of ingesting expired cells educates the immune system in how to maintain tissues in a clean and healthy state, and that macrophages play a very important role in this process. The study identifies in detail the molecules that carry out important tasks in the phagocytic process in each tissue, from the gut to the liver and bone marrow. Surprisingly, the researchers found that each tissue has its own specific molecular toolkit for eliminating unwanted cells. According to Alonso-González, "This discovery suggests that it should in principle be possible to modulate phagocytosis in individual organs, without altering events in neighboring organs. One could, for example, promote the elimination of dangerous cells in the spleen without risking elimination of beneficial cells in the lung."

Although any therapeutic application lies in the future, in describing how the organism maintains itself clean and healthy, the study suggests that in time it may be possible to coordinate the work of these cleansing macrophages to our benefit. The researchers quip that "in our bodies, as in society, diet, education, and cleanliness are the keys to maintaining harmony."
-end-


Centro Nacional de Investigaciones Cardiovasculares

Related Immune System Articles:

Memory training for the immune system
The immune system will memorize the pathogen after an infection and can therefore react promptly after reinfection with the same pathogen.
Immune system may have another job -- combatting depression
An inflammatory autoimmune response within the central nervous system similar to one linked to neurodegenerative diseases such as multiple sclerosis (MS) has also been found in the spinal fluid of healthy people, according to a new Yale-led study comparing immune system cells in the spinal fluid of MS patients and healthy subjects.
COVID-19: Immune system derails
Contrary to what has been generally assumed so far, a severe course of COVID-19 does not solely result in a strong immune reaction - rather, the immune response is caught in a continuous loop of activation and inhibition.
Immune cell steroids help tumours suppress the immune system, offering new drug targets
Tumours found to evade the immune system by telling immune cells to produce immunosuppressive steroids.
Immune system -- Knocked off balance
Instead of protecting us, the immune system can sometimes go awry, as in the case of autoimmune diseases and allergies.
Too much salt weakens the immune system
A high-salt diet is not only bad for one's blood pressure, but also for the immune system.
Parkinson's and the immune system
Mutations in the Parkin gene are a common cause of hereditary forms of Parkinson's disease.
How an immune system regulator shifts the balance of immune cells
Researchers have provided new insight on the role of cyclic AMP (cAMP) in regulating the immune response.
Immune system upgrade
Theoretically, our immune system could detect and kill cancer cells.
Using the immune system as a defence against cancer
Research published today in the British Journal of Cancer has found that a naturally occurring molecule and a component of the immune system that can successfully target and kill cancer cells, can also encourage immunity against cancer resurgence.
More Immune System News and Immune System Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: The Power Of Spaces
How do spaces shape the human experience? In what ways do our rooms, homes, and buildings give us meaning and purpose? This hour, TED speakers explore the power of the spaces we make and inhabit. Guests include architect Michael Murphy, musician David Byrne, artist Es Devlin, and architect Siamak Hariri.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

What If?
There's plenty of speculation about what Donald Trump might do in the wake of the election. Would he dispute the results if he loses? Would he simply refuse to leave office, or even try to use the military to maintain control? Last summer, Rosa Brooks got together a team of experts and political operatives from both sides of the aisle to ask a slightly different question. Rather than arguing about whether he'd do those things, they dug into what exactly would happen if he did. Part war game part choose your own adventure, Rosa's Transition Integrity Project doesn't give us any predictions, and it isn't a referendum on Trump. Instead, it's a deeply illuminating stress test on our laws, our institutions, and on the commitment to democracy written into the constitution. This episode was reported by Bethel Habte, with help from Tracie Hunte, and produced by Bethel Habte. Jeremy Bloom provided original music. Support Radiolab by becoming a member today at Radiolab.org/donate.     You can read The Transition Integrity Project's report here.