A key immune system component called memory T-cells contributes to the naturally occurring protection against pneumonia-causing bacteria that the body develops during childhood, according to a study.
The research, “Regionally compartmentalized resident memory T cells mediate naturally acquired protection against pneumococcal pneumonia,” was published in the journal Mucosal Immunology.
During childhood, we are more susceptible to infections, such as those targeting the lungs. As we age, our susceptibility decreases because our immune system’s memory increases its performance against new infections that pop up.
Boston University Medical Center researchers have discovered that recovering from bacterial pneumonia changes lung tissue by flooding it with a special group of immune cells called CD4 resident memory T (TRM) cells.
Different levels of TRM cells in the lungs can influence young children and older adults’ susceptibility to pneumonia, the researchers said. The findings suggest that manipulating the number and activity of the cells could become a new path for treating pneumonia.
Researchers infected the airways of mice with Streptococcus pneumonia. They discovered that previous infections had indeed provided protection against virulent pneumonia bacteria. A key result was a significant reduction in the bacterial burden.
Depleting TRM cells before introducing another Streptococcus pneumonia led to the mice losing their protection. This meant that the TRM cells were the reason for the protection.
Another indication that TRM cells were the protective agents was that the cells were found only in the infected area, and were not dispersed across the lower respiratory tract. Importantly, the TRM-provided protection was also confined to the immunologically active area of the lung.
“Our study suggests that respiratory bacterial infections during childhood establish a novel type of antibacterial immunity,” Joseph Mizgerd, the study’s lead author, said in a press release. “The TRM cells left behind after prior infections are more broadly effective than vaccine-generated immunity, providing protection against a wider spectrum of microbes that can infect the lungs,” said Mizgerd, a professor of medicine, microbiology and biochemistry at the Boston University School of Medicine.
While the study provided a new piece of the puzzle about our immune system’s strategies for preventing pneumonia during childhood, the question of whether the mechanism is also present in healthy young adults remains unknown.
“We have only modest abilities to prevent or cure many of the infections that cause pneumonia,” Mizgerd said. “Defining the protective mechanisms normally preventing lung infections in most young healthy adults will lead to tests identifying who is susceptible and new approaches for preventing and treating the infections.”