Washington, June 10 : Researchers from Ohio State University have revealed that boosting the immune system in elderly people is the most effective way to help them fight against tuberculosis.
Joanne Turner, an assistant professor of internal medicine at Ohio State University and Barbara Szomolay, a postdoctoral researcher in Ohio State's Mathematical Biosciences Institute created a mathematical model to understand the concept clearly.
During the study, the researchers found that simulations of TB infection in an old mouse showed that increasing the number of infection-fighting white blood cells, called CD4 T cells, could be particularly effective at bolstering the mouse's immune response, which naturally slows with aging.
Older humans have similar delays in their immune response, meaning that they have a much more difficult time controlling TB than do younger people with an active infection.
The math modelling also suggested that making changes to macrophages, cells that essentially eat infecting bacteria, could enhance those cells' interactions with other warriors in the immune system, reducing the concentration of bacteria in the lungs associated with TB infection.
"This modelling is giving us clues as to what would help an older person control infection," Turner said.
"In thinking about therapies, if we find a way to make older people have a better T-cell response, such as with vaccination, or by giving them a post-exposure therapy in the lung that would activate the macrophage better, either way they should be able to control infection more effectively," she added.
The elderly are considered highly susceptible to both reactivation of latent TB infection and newly acquired infections, especially in long-term care facilities.
Many older patients cannot tolerate the antibiotic regimen required to treat active TB.
The immune response to TB infection is complex, and aging affects that process. In fighting infections, two immune responses occur: The innate immune response begins a fight against any pathogen. The acquired immune response follows, with components designed to fight the specific pathogen causing the infection.
Older people, and mice, have a strong innate immune response that enables them to initially control bacteria from TB and other infectious diseases.
The two most effective methods found to improve infection control in the old mouse model were increasing the number of CD4 T cells present early on in the infection, and increasing the number of specialized molecules on the surface of macrophages, enhancing the visibility of the TB bacteria.
"We showed that we could change the control of infection, but we could never get that old mouse to look like a young mouse, which means that there's more to the immune system defect than just the initial interaction between the T cell and macrophage," said Turner.
The research appears in a recent issue of the journal Experimental Gerontology.