Dysfunctional bronchoalveolar effector memory CD8+ T cells in tuberculosis-exposed people living with antiretroviral-naïve HIV infection

AI Summary

This study explored how a specific type of immune cell behaves in the lungs of people who have been exposed to tuberculosis (TB) and are living with untreated HIV. The researchers collected both blood and fluid from deep in the lungs from adults who had evidence of past TB exposure but no active disease. Half of the participants were living with HIV and had not yet started HIV treatment. They compared immune activity in these samples to understand how HIV affects the ability of lung immune cells to fight infections.  

They found that HIV infection changed immune activity differently in blood and lung fluid. In lung fluid, people with HIV had higher numbers of a particular immune cell called effector memory CD8⁺ T cells, but these cells showed signs of dysfunction. Importantly, these cells produced less of a signalling protein called IL‑17A, which normally helps defend against bacteria in the lungs. The reduced production of this molecule was linked with higher expression of regulatory molecules that can dampen immune responses. 

Meanwhile, in blood samples from people with HIV, there were stronger signals of immune activation and cell growth compared to people without HIV.  

Overall, the findings suggest that uncontrolled HIV alters immune responses in the lungs. Even though some immune cells are present in higher numbers, they are less able to carry out key functions needed to protect against respiratory infections like TB. This may help explain why people with untreated HIV are more vulnerable to lung infections, and points toward the need to explore therapies that can restore the function of these lung immune cells.