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Understanding recurrent tonsillitis

Researchers may have figured out why some people are susceptible to recurrent tonsillitis. LightFieldStudios / iStock / Thinkstock

Tonsillitis, or swelling of the tonsils, is usually caused by a viral infection. But it can also be caused by strep bacteria, Streptococcus pyogenes. Parents of young children are all too familiar with the symptoms of this type of tonsillitis, also known as strep throat. These can include fever, a sore throat, and swelling in the lymph nodes and tonsils.

Strep throat can be treated effectively with antibiotics, but some children get the disease repeatedly (recurrent tonsillitis). Children who develop recurrent tonsillitis may need to have their tonsils surgically removed. It hasn’t been clear why some children are more likely than others to get recurrent tonsillitis.

To gain a better understanding, a team led by Dr. Shane Crotty from the La Jolla Institute for Immunology acquired tissue samples from the tonsils of 66 children who had them removed due to recurrent tonsillitis and 80 children who had them removed for other medical reasons, such as sleep apnea. The study was funded in part by NIH’s National Institute of Allergy and Infectious Diseases (NIAID). Results appeared on February 6, 2019, in Science Translational Medicine.

T follicular helper (T_FH) cells are a type of immune cell that normally help another type of immune cell (B cells) produce protective antibodies against bacteria and viruses. The team found that the tonsils of children with recurrent tonsillitis contained relatively higher numbers of a novel T_FH cell type. The children with recurrent tonsillitis also had fewer B cells in their tonsils.

Naïve B cells (blue) team up with T follicular helper cells (white) in areas known as germinal centers (red) within tonsils. This interaction allows them to become mature, antibody-producing B cells (green). Dr. Yu Kato, La Jolla Institute

When people are exposed to S. pyogenes, their immune system produces several antibodies, one of which recognizes a toxic protein produced by the bacteria called SpeA. The scientists found that children with recurrent tonsillitis had low levels of antibodies against SpeA in their blood. Further experiments found that in these children, the bacteria were playing a dirty trick on the immune system. The SpeA caused the novel T_FH cells to kill B cells instead of helping those B cells to make antibodies to neutralize, or inactivate, the SpeA toxin.

Vulnerability to this process appears to have a genetic component. The researchers saw that many of the children in their study had a family history of recurrent tonsillitis. The team was able to identify specific genetic variations in the immune system that were associated with risk of recurrent tonsillitis.

These findings point to potential strategies to reduce the incidence of recurrent tonsillitis.

“Since the immunological connection as well as the genetic connection are all tied to an insufficient antibody response against SpeA, it suggests that recognizing this factor is actually a key problem for these kids,” Crotty says. “Having a vaccine that trains the immune system in advance might be able stimulate a protective immune response that can prevent recurring bouts of tonsillitis.”