Irish scientists have taken a big step in understanding how human lungs fight tuberculosis (TB). Their discovery could lead to the development of new treatment approaches for the disease.

TB is a serious bacterial disease that usually affects the lungs, but can also affect other parts of the body. Symptoms can include fever, coughing, weight loss, night sweats and blood in the phlegm.

TB remains a major public health issue globally and is currently the world's number one infectious killer. Figures from the World Health Organization show that in 2013, an estimated nine million people developed it and 1.5 million died from the disease.

In 2014, 328 cases of the disease were notified in Ireland. However more worryingly, there have been dozens of cases of multidrug-resistant TB and four cases of extreme drug-resistant TB notified here.

Because of the disease's increasing resistance to antibiotics, the need to find new treatments is critical.

It is already known that half of infected people clear the invading TB bacteria after inhaling it into their lungs. However until now, it was not known how the immune system in the lungs managed to do this.

Now, scientists at Trinity College Dublin (TCD) and St James's Hospital, working with teams from the University of Cambridge in the UK and the University of Seattle in the US, have identified a way that TB hijacks the immune cells in the early stages of infection and allows it to establish an infection in the lungs.

They found that the most virulent strains of TB bacteria are able to hijack specialised immune cells in the lungs, known as alveolar macrophages, which are the first responders to bacterial infections. This causes the cells to produce a protein that attracts white blood cells from circulation. These white blood cells fuse with the macrophages and in turn become infected.

The Irish part of the study included using donated lung macrophage samples from patients in St James's Hospital to study the response of the human immune system to TB in the early stages of infection.

"We are fascinated how TB bacteria virulence factors can corrupt this human lung immune cell, which is ordinarily exceptionally good at clearing infection. It's very exciting to work with our Cambridge colleagues on this research which improves our understanding of how TB infection compromises immunity.

"We are in a unique position to address the important challenges for TB treatment as we work with the human lung model. This allows us to continue in our research to design novel ways to support the effective lung cell and prevent infections in exposed people," commented Dr Seónadh O' Leary, a senior research fellow at TCD.

The Irish team is now hoping to identify drugs that will enable these immune cells to stop the infection in its tracks, by killing the TB bacteria before they attract white blood cells to the lung.

According to Mairead O'Driscoll, interim CEO at the Health Research Board, which helped to fund this research, these findings represent ‘a significant breakthrough in our understanding of how the bacteria avoids our immune system'.

"Antidrug resistant TB is a global problem and we're delighted to be able to facilitate international collaboration to tackle this challenge. Ireland is lucky to have such brilliant researchers, who are genuine world leaders in their fields," she said.

Details of these findings are published in the journal, Immunity.