Researchers have identified a master cell that coordinates the body's immune response in the early days of TB infection.

According to the study published in the journal Nature, the researchers found that boosting the activity of such cells could help reduce the millions of new infections that occur worldwide every year. For the study, the researchers from Washington University School of Medicine and Africa Health Research Institute carried out research on animals and people to identify the immune cells that defend the body against the TB bacteria in the first days after infection.

They found that cells known as group 3 innate lymphoid cells (ILC3) play a pivotal role in the first two weeks of infection. ILC3 cells belong to the innate branch of the immune system that detects and responds to foreign invaders in the body.  "The immune response to the TB bacteria hinges on the early response of this cell, and that opens up a whole new avenue for TB control," said the study's co-senior author Shabaana Abdul Khader, Professor at Washington University School of Medicine, US.

Experiments showed that within five days after infection, ILC3 cells show up in the lungs, where they release chemical compounds that activate and attract other immune cells. The arriving cells include other innate immune cells - which come loaded with bacteria-killing weapons - as well as adaptive immune cells that direct and enhance the innate immune cells' killing potential. Together, the immune cells surround the bacteria and destroy them. "These innate lymphoid cells seem to orchestrate all the early downstream immune responses, both innate and adaptive, that you need to control infection," noted Khader.

The researchers have begun screening a set of chemical compounds, looking for ones that enhance ILC3 activity and drive a stronger immune response in the first day after infection. "The more we can understand about the interaction between the bacteria that cause TB and people, the more chance we have of building on these gains and defeating this deadly epidemic," said the study's co-senior author Alasdair Leslie, a faculty member from Africa Health Research Institute, South Africa.

The researchers maintained that they wouldn't want to replace the BCG vaccine. "We may be able to find a compound that we can use to boost immunity in vaccinated children when the effects of the BCG start to wear off," Khader said. According to the World Health Organization (WHO), about 1.5 million people died of TB in 2017, making it the most lethal infectious disease worldwide.