Boosting Immunity in Older Adults
Sixty-five is the age when many people retire, kick back, and take it easy. And so it often is with the human immune system.
After years of fending off influenza and other infectious diseases, the immune system gradually starts to lose its oomph for fighting infection. As a result, viruses, bacteria, and other microbial intruders are a common killer of adults 65 and older.
However, a study led by the University of Arizona Health Sciences Department of Immunobiology and published June 6th 2016 online before print in Nature Immunology.shows it may not have to be that way.
A release from the university explains that the researchers examined blood samples from 92 volunteers, age 21 to 97. The team focused on a subset of T cells – white blood cells that fight infection and decrease in number as adults age – specifically, T cells labeled “naïve” because they have not yet been exposed to a virus or other infection.
The release quotes Janko Nikolich-Žugich, MD, PhD, head of the Department of Immunobiology and Elizabeth Bowman Professor of Medical Research at the and the study’s principal investigator, as saying, “When there is an infection, like an influenza virus, for example, a small cohort of these naive T cells – only those that have special molecules on their surface that will bind to fragments of the influenza – are deployed in a very targeted manner.”
These deployed naive T cells then become effector T cells, he said. Unlike the naive cells, which cannot harm the virus, effector cells are “armed” and able to clear the virus using antiviral molecules they now make. “Once they have done away with the infection, most of the effector T cells will die, but a substantial number will survive and become ‘memory’ cells,’ which will remember and fight off an infection, if and when it recurs,” Dr. Nikolich-Žugich said.
The breakthrough came when the researchers, focusing on navie T cells, discovered that when stimulated with pieces of virus, a portion of the cells began making interferon-gamma, a powerful anti-viral molecule.
They found that among these naive cells – which now looked functionally more like memory cells – many were marked to attack cytomegalovirus (CMV), a type of herpes virus that infects most people and is carried for life without harm, kept in check by a highly functioning immune system, but devastating to those with suppressed immune systems, including older adults.
These naive T cells are “a new ‘flavor’ of naive cells that are not completely naive,” Dr. Nikolich-Žugich said. “So our new discovery is that there is more diversity than we realized within the naïve cells, and that some already have committed to dealing with CMV and other really persistent infections, and others are really, truly naive.”
Dr. Nikolich-Žugich and his colleagues have named the “new flavor” of T cells “T memory cells with naive phenotype.”