In Brief

Tai chi gives immune system a boost

Fighting off diseases is a young person's game. With age, our immune systems become less nimble and not quite as ruthless. The number of T cells drop. The B cells also start to wind down, making fewer antibodies that respond to outside intruders and more errant ones that turn on the body itself.

As a result, even those of us who age gracefully are more vulnerable to getting sick as we tack on the years. What's more, our immune systems don't respond as vigorously to the vaccinations — such as the annual flu shot — that we get to prevent some of those illnesses.