Scientists in Australia have identified how human immune cells detect bacteria, a discovery that could lead to effective vaccines and therapies for many diseases.

Researchers at Australia's Peter Doherty Institute for Infection and Immunity found that macrophages -- immune cells known for engulfing pathogens -- act as "couriers" that alert the immune system to bacterial presence, a media release from the Doherty Institute said late Tuesday.

"This activates the immune system and helps our body stay in balance with the good bacteria that live within us (forming the microbiota) while protecting us from dangerous bacteria," according to Deng Jieru from the University of Melbourne, who conducted postdoctoral research at the Doherty Institute.

The study shows macrophages carry the highest amount of a molecule called MR1, which captures chemical signals from bacteria and presents them to specialized immune cells known as MAIT cells.

"By using glowing 'chemical messages' we showed that macrophages were the most efficient cells at picking messages and to use this to engage MAIT cells to fight infections," said Deng, who led the study published in Science.

This discovery is important because MAIT cells can rapidly "switch on" powerful immune responses, she said, adding that by understanding how macrophages control this process, this discovery paves the way for better vaccines and treatments.