A new study from the Trudeau Institute in Saranac Lake, New York, demonstrates that immune system cells important for both pathogen resistance and vaccine efficacy live longer in older animals but because of this longevity acquire functional defects. The work may provide new targets for boosting immune system function in older individuals.
The well-documented decreases in immune system function that accompany aging leave elderly individuals more susceptible to numerous infectious agents than younger people. Thus many vaccines now in use are not nearly as effective in protecting older people. For example, a Journal of the American Medical Association study found that in individuals over the age of 70, influenza vaccination offered only 23 percent protection, and reduced responses have also been seen for tetanus and hepatitis vaccinations.
In previous work, Trudeau Institute Investigator Susan Swain and her colleagues demonstrated that a specific type of immune cells, called CD4 T cells, which are critical to vaccine response, become less effective with age. Robust CD4 activity is necessary for antibody production in response to infection or vaccination. (The immune system contains a number of different cell types including B cells, which manufacture antibodies, and multiple classes of T cells. CD4 T cells are a type of helper cell that stimulates B cell production and many other components of immunity.) Specifically, "naive" CD4 T cells, those that have not come into contact with or become specialized to respond to a particular pathogen, are needed to ensure protection against new pathogens as well as vigorous responses to vaccination.