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Researchers Find Intestinal Immune Cell Prevents Food Allergies
Most of the time, the intestinal immune system can recognize friend from foe, tolerating myriad foods while destroying disease-causing invaders. But for approximately 30 million Americans with food allergies -- including 4 million children -- immune cells mistakenly identify food as a threat, triggering potentially life-threatening reactions.
Now, researchers at Washington University School of Medicine in St. Louis have identified, in mice, that essential immune cells in the intestine prevent an unwarranted attack against harmless food allergens. In the absence of such cells, mice experienced gut inflammation and an allergic response to food.
Their research was published online April 3 in Cell and will appear in print May 15.
"We are seeing a rapid global increase in food allergies that significantly impact quality of life," said Marco Colonna, MD, the Robert Rock Belliveau, MD, Professor of Pathology at WashU Medicine. "The lack of therapeutics to prevent and manage food allergies complicates the growing public health issue. Now that we know the players that establish tolerance to food allergens, we can devise innovative strategies to target them therapeutically and potentially prevent or treat food allergies."
The immune system encounters common food allergens -- peanuts, tree nuts, milk, eggs and shellfish, among others -- without launching a self-sabotaging immune attack in a process called tolerance. Broken tolerance to food triggers an allergic reaction with symptoms ranging from mild hives and itching to a severe, life-threatening allergic reaction that can cause throat swelling and difficulty breathing and requires immediate treatment. As part of the current study, the researchers aimed to home in on the players working to prevent such reactions, in work that may help develop preventive treatments for food allergies.
Tolerance to food involves multiple immune cells. Certain immune cells pick up food particles, chop them into fragments and present them to the immune system's T cells, instructing those cells to remain unresponsive to the harmless intruder. More recently, a small population of cells -- the RORγt+ dendritic cells -- has been found among the gut's presenting immune cells in multiple species. Colonna's lab was the first to identify the cells in people in 2023. Their role in preventing food allergies had not been explored.
Patrick Rodrigues, PhD, a postdoctoral scholar, and Shitong Wu, an MD/PhD student, in Colonna's lab and the study's co-first authors, set out to understand whether RORγt+ dendritic cells are the gut's immune cells that prevent food allergies. They treated mice with ovalbumin, a highly allergenic protein found in egg whites, orally and then intranasally. Mice lacking gut RORγt+ dendritic cells showed signs of allergic lung inflammation, while mice with these cells did not. An analysis of the gut immune cells found an imbalance among the T cells that trigger versus dampen immune responses to food particles in the allergic mice, with a skewing toward the former.
"By removing RORγt+ dendritic cells from the gut in mice, we broke tolerance to food allergens," said Rodrigues. "The discovery is now inspiring us to see if we can do the opposite: prevent food allergies by supporting the activity of this cell population. Because RORγt+ dendritic cells are found in people, our finding presents an exciting new possibility to manage food allergies and other gut-related immune diseases such as celiac disease or inflammatory bowel disease."
Recently, the FDA approved an injectable medication, that, if administered continuously, helps prevent an allergic response to accidental exposure to small amounts of allergens by blocking the antibodies that result from an activated immune response. Avoiding the allergen and carrying an EpiPen is still recommended for individuals on the medication.
"Targeting the activity of RORγt+ dendritic cells has the potential to work even further upstream to prevent an immune response from first being triggered," said Wu. "If that proves to be true, a therapy supporting the activity of this small population of cells might offer lasting tolerance to food allergens."
What To Know About Nausea After Eating
Eating too much food in one sitting can cause feelings of nausea. However, there are many other possible causes, such as an infection, an ulcer, pregnancy, bulimia, and medication use.
Nausea refers to a feeling of sickness or discomfort in the stomach that may result in an urge to vomit. There are many possible reasons that a person may feel nauseous after eating. These can range from eating too much, to certain conditions.
The conditions that cause nausea after eating range from mild to severe. This article will outline what these disorders are, how to tell what is causing the nausea, and how to avoid or treat it
The digestive system refers to a collection of organs that work together to break down food and drink. They digest what is consumed, turning nutrients into energy that the body can use for functioning or store for later use.
The digestion process begins in the mouth, where food is broken down so that it can be swallowed. Food then travels down the food pipe (esophagus) towards the stomach and intestines. The digestive juices in the stomach and intestines break down the food for the final time and extract the nutrients. The waste passes into the large intestine for excretion through the anus.
Any problems during this digestive process can cause nausea after eating.
Symptoms will often develop in the stomach or upper abdominal area, where the large-scale breakdown of food begins. People may also experience other symptoms, such as diarrhea, headaches, or heartburn.
Sometimes the body reacts to these problems by forcibly emptying the stomach, usually through vomiting. The problem can sometimes be identified by the color of the vomit. For example, a bright yellow or dark green color may indicate a problem in the small intestine.
Causes of how nausea develops after eating can include:
Hormonal
Hormonal changes often occur during pregnancy, which induce feelings of nausea at any time of day, frequently in the morning. Some pregnant women will experience nausea before eating a meal. Others will feel nauseated immediately after eating. Sometimes this continues throughout the day.
Feelings of nausea will typically start during the second month of pregnancy. Nausea during pregnancy is not harmful to either the baby or mother and will usually resolve by the fourth month of pregnancy.
Elevated hormone levels in pregnancy can cause changes to the digestive system and the body, which means food spends longer in the stomach and small intestine. It is possible that this may also contribute to nausea after eating in pregnancy.
Infection
Food can become contaminated through not being cooked thoroughly or stored incorrectly. Consuming contaminated food can cause food poisoning. Bacteria (or in some cases, viruses) are usually the cause of contamination. Either can induce feelings of nausea within hours of eating.
These infections cause inflammation to the stomach and intestines. They can lead to:
Food intolerances or allergies
Food intolerances do not involve the immune system but can cause nausea hours after the food is eaten. Common sources of food intolerances include:
Food allergies occur when the body mistakenly identifies proteins found in certain foods to be a threat, triggering an immune system response.
Nausea caused by a food allergy can occur seconds or minutes after eating. It is often accompanied by a host of other symptoms, such as swelling to the face or lip and difficulties breathing or swallowing. These types of reactions are emergencies and require immediate medical attention.
Gastrointestinal problems
Nausea after eating and other gastrointestinal problems may occur when an organ within the digestive system stops functioning properly.
For example, gastroesophageal reflux disease (GERD) occurs when the ring of muscle between the esophagus and stomach malfunctions, causing stomach acid to enter the esophagus. GERD causes a burning sensation throughout the esophagus known as heartburn and may be a cause of nausea after eating.
The gallbladder is responsible for releasing bile to aid in digesting fats. Gallbladder diseases impair the proper digestion of fats and can cause nausea after eating meals high in fat.
The pancreas releases proteins and hormones necessary for digestion. If this organ becomes inflamed or injured, known as pancreatitis, nausea often occurs along with other intestinal symptoms and pain.
Irritable bowel syndrome (IBS) is a chronic condition that can cause bloating and increased gas. In some people, this can also lead to nausea after eating.
Other conditions that can cause meal-related nausea and vomiting can include:
It is also possible for cancers that affect the GI tract to cause nausea. These may include:
Vascular
Bowel ischemia is a rare circulatory condition which can link with other circulatory diseases. Nausea after eating could be a sign of arteries in the intestines narrowing. This narrowing of blood vessels restricts blood flow, which can damage the intestines.
Nausea after eating can be accompanied by intense stomach pains and may indicate a condition known as chronic mesenteric ischemia. This condition can suddenly worsen and become life-threatening.
Headache syndromes
Migraines can also cause nausea after eating, which can be accompanied by intense stomach pain, vomiting, and dizziness.
Cardiac
Psychiatric or psychological
Anorexia nervosa can cause nausea due to excess stomach acid or starvation. Bulimia nervosa can cause nausea after eating from a compulsion to vomit any food consumed.
Motion sickness
Some people are highly sensitive to particular movements or motion, which can make them feel nauseated. Eating food before or after experiencing motion can intensify nausea in individuals with motion sickness.
Medications
Typically, nausea after eating is not related to a serious condition. If it continues for more than 5 days or if some of the symptoms mentioned above occur together, people should contact a doctor to rule out an underlying condition.
Children who experience nausea after eating may need more attention. Contact a doctor if:
For adults, it is advisable to consult a doctor if they experience:
The causes of nausea are wide ranging. But recording exact times of nausea and food consumed can help a doctor make a diagnosis.
Depending on the suspected cause, getting a full diagnosis could involve:
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