Special immune cells keep TB in control: study

A special class of immune cells called 'invariant natural killer T cells' keep the deadly tuberculosis infection in check - a heartening news for India that has the most number of tuberculosis cases in the world.

"Mycobacterium tuberculosis is a major cause of death worldwide. Most healthy people can defend themselves against tuberculosis, but they need all parts of their immune system to work together. We were interested in identifying the mechanisms that different types of T cells use to control Mycobacterium tuberculosis infection," said senior author Samuel Behar of University of Massachusetts Medical School, US.

His team found that when 'invariant natural killer T cells' encounter infected macrophages - the human target cells of Mycobacterium tuberculosis (Mtb) - T cells somehow prevented Mtb from growing and multiplying inside the macrophages.

Using a number of cell culture systems and experiments in mice to dissect the interaction, they found that when T cells are confronted with Mtb-infected macrophages, they respond in two different ways.

One is that they produce and release interferon gamma, a broad-spectrum immune system activator. But when the scientists blocked interferon gamma action, they found that the T cells could still inhibit Mtb growth in the macrophages, said the study published in the journal PLOS Pathogens.

"Understanding how such T cells contribute to the control and elimination of Mtb could lead to novel therapeutic approaches that strengthen their activity and boost the overall immune response during infection," concluded the study.