What’s behind frequent strep throat? Consult the tonsils | Science News for Students

What’s behind frequent strep throat? Consult the tonsils

Immune problems may be one source — stowaway germs may give faulty diagnoses
Mar 15, 2019 — 6:45 am EST
a close-up photo of a child's open mouth with a tongue depressor holding the tongue down

The germs that cause strep throat infections can hide out in the tonsils.

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For kids, getting strep throat over and over is a pain. It’s also a problem that has puzzled scientists. Now a study of kids’ tonsils suggests what’s up. Some kids have a faulty immune response to strep bacteria. Others are misdiagnosed with the disease when strep germs hide out in their tonsils.

That’s the finding of a study published online February 6 in Science Translational Medicine.

Each year, strep throat sickens some 600 million people across the globe. Bacteria called group-A Streptococcus are to blame. The sickness can cause a sore throat, fever and more. Kids who get the disease are at risk of heart problems and rheumatic fever (a non-infectious but very serious disease).

Doctors treat strep throat with antibiotics. Still, some treated kids keep getting strep throat again and again. These children and teens tend to have smaller immune structures in their tonsils than kids who hadn’t had repeated infections, a new study finds. Those immune structures help make antibodies — proteins that fight off bacteria and viruses.

Tonsils may be key

Shane Crotty studies the immune system at the La Jolla Institute for Immunology. It’s in Southern California. For a new study, he and his colleagues examined tonsils from kids 5- to 18-years old. Some had their tonsils taken out because of frequent strep throat. Others had theirs removed to fix breathing problems caused by big tonsils. This second group was a stand-in for kids who don’t get recurring strep throat.

The team looked at pieces of the tonsils under a microscope. Kids with recurring strep had smaller immune structures called germinal (GER-mih-nul) centers. And these centers made fewer immune cells known as T cells. T cells help other immune cells known as B cells make antibodies.

an image showing the difference immune structures in the tonsils of kids who had repeated strep throat infections versus those who did not
Kids with repeated bouts of strep throat had smaller immune structures (brown) in their tonsils (left in these microscope images) than kids who without repeat infections (right). 
J.M. DAN ET AL/SCIENCE TRANSLATIONAL MEDICINE 2019

Infection-fighting antibodies come in many forms. Kids with recurring strep had fewer of these that respond to a protein in group A strep. That protein helps the microbe mess with the immune system. That protein may leave kids more prone to future infections, Crotty says.

The research is elegant and intriguing, says Stanford Shulman. He is a doctor that studies infectious disease in kids. Shulman works at the Ann & Robert H. Lurie’s Children’s Hospital of Chicago in Illinois. He was not involved in the research.

But sometimes, Shulman warns, kids diagnosed with recurrent strep throat aren’t sick. Because of some earlier infection, strep bacteria now live harmlessly in their tonsils. In such cases, a sore throat due to a virus might now be mistaken as strep throat. The reason? Tests can turn up signs that the body hosts the strep germ. An estimated 20 percent of school-aged kids are such chronic hosts of group A strep.

It’s possible some kids in the study’s recurrent strep-throat group were carriers, too, Shulman says. Future work, Shulman says, should determine which kids truly get repeat strep throat infections and which kids are strep carriers who might have been sickened this time by something else.

Power Words

(more about Power Words)

antibiotic     A germ-killing substance, usually prescribed as a medicine (or sometimes as a feed additive to promote the growth of livestock). It does not work against viruses.

antibody     Any of a large number of proteins that the body produces from B cells and releases into the blood supply as part of its immune response. The production of antibodies is triggered when the body encounters an antigen, some foreign material. Antibodies then lock onto antigens as a first step in disabling the germs or other foreign substances that were the source of those antigens. 

bacteria     (singular: bacterium) Single-celled organisms. These dwell nearly everywhere on Earth, from the bottom of the sea to inside other living organisms (such as plants and animals).

B cell     A type of small white blood cell (also known as a B lymphocyte), which plays an important role in the immune system. Made in the bone marrow, these cells mature into plasma cells, and serve as the source of antibodies.

carrier     (in medicine) A person or organism that has become infected with an infectious disease agent, but displays no symptoms. The infamous “typhoid Mary” was a well-known example — an individual who could infect others with a killer disease but showed no signs of disease herself.

cell     The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Most organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.

chronic     A condition, such as an illness (or its symptoms, including pain), that lasts for a long time.

colleague     Someone who works with another; a co-worker or team member.

disrupt     (n. disruption) To break apart something; interrupt the normal operation of something; or to throw the normal organization (or order) of something into disorder.

immune     (adj.) Having to do with the immunity. (v.) Able to ward off a particular infection. Alternatively, this term can be used to mean an organism shows no impacts from exposure to a particular poison or process. More generally, the term may signal that something cannot be hurt by a particular drug, disease or chemical.

immune system     The collection of cells and their responses that help the body fight off infections and deal with foreign substances that may provoke allergies.

immunology     The field of biomedicine that deals with the immune system. A doctor or scientist who works in that field is known as an immunologist.

infection     A disease that can spread from one organism to another. It’s usually caused by some type of germ.

infectious     An adjective that describes a type of germ that can be transmitted to people, animals or other living things.

microbe     Short for microorganism. A living thing that is too small to see with the unaided eye, including bacteria, some fungi and many other organisms such as amoebas. Most consist of a single cell.

microscope     An instrument used to view objects, like bacteria, or the single cells of plants or animals, that are too small to be visible to the unaided eye.

online     (n.) On the internet. (adj.) A term for what can be found or accessed on the internet.

protein     A compound made from one or more long chains of amino acids. Proteins are an essential part of all living organisms. They form the basis of living cells, muscle and tissues; they also do the work inside of cells. Among the better-known, stand-alone proteins are the hemoglobin (in blood) and the antibodies (also in blood) that attempt to fight infections. Medicines frequently work by latching onto proteins.

risk     The chance or mathematical likelihood that some bad thing might happen. For instance, exposure to radiation poses a risk of cancer. Or the hazard — or peril — itself. (For instance: Among cancer risks that the people faced were radiation and drinking water tainted with arsenic.)

strep     Short for streptococcus. This is a family of bacteria — some of which can cause a fever, swollen tonsils and a severe sore throat, especially in children.

symptom     A physical or mental indicator generally regarded to be characteristic of a disease. Sometimes a single symptom — especially a general one, such as fever or pain — can be a sign of any of many different types of injury or disease.

T cells     A family of white blood cells, also known as lymphocytes, that are primary actors in the immune system. They fight disease and can help the body deal with harmful substances.

tissue     Made of cells, it is any of the distinct types of materials that make up animals, plants or fungi. Cells within a tissue work as a unit to perform a particular function in living organisms. Different organs of the human body, for instance, often are made from many different types of tissues.

tonsils     Short for palatine tonsils. This is a pair of soft tissues at the back of the throat. They are part of the immune system, which can help to fight infections. Many people get infected tonsils removed, however, and seem no more vulnerable to infection afterward. The tonsils’ structure somewhat resembles that of lymph nodes. The tonsils’ outer pink cover is similar to that of the mouth’s lining.

virus     Tiny infectious particles consisting of RNA or DNA surrounded by protein. Viruses can reproduce only by injecting their genetic material into the cells of living creatures. Although scientists frequently refer to viruses as live or dead, in fact no virus is truly alive. It doesn’t eat like animals do, or make its own food the way plants do. It must hijack the cellular machinery of a living cell in order to survive.

Citation

Journal:​ ​​J.M. Dan et al. Recurrent group A Streptococcus tonsillitis is an immunosusceptibility disease involving antibody deficiency and aberrant TFH cells. Science Translational Medicine. Vol. 11, February 6, 2019, p. eaau3776. doi: 10.1126/scitranslmed.aau3776.