When Boston's legendary mobster James "Whitey" Bulger claimed he had immunity from murder charges because of a deal he made with a deceased prosecutor, it didn't keep him out of hot water.

Seems sometimes (supposed) immunity is effective, and sometimes, well, you're not protected.

The same can be said about your immune system, that incredibly complex mixture of defense and prosecutorial cells inside you. And recently, researchers have been making amazing discoveries about its powers to protect (or harm) your health.

Case in point: There's now an anti-cancer treatment that empowers your immune system's warrior T cells to knock out multiplying cancer cells. Seems researchers used certain antibodies to "unlock" the tumor-attacking ability of T cells in nearly 300 people; 28 percent of folks with melanoma (the deadliest skin cancer) saw their tumors shrink; the same positive results happened for 27 percent of the study participants with kidney cancer and 18 percent with lung cancer.

Meanwhile, researchers at Columbia University announced that for some people, Parkinson's disease, which affects more than 1 million North Americans, may turn out to be an autoimmune disorder.

That means the neurological symptoms of Parkinson's disease - tremors and shaking, for example - occur because immune-system cells mistakenly attack and kill specific neurons.

This controversial idea could lead to new ways to treat and prevent the condition.

Next on the list, Emory University scientists are rebooting the immune systems of organ-transplant recipients to cut down on the need for toxic anti-rejection drugs. Even the U.S. military is getting into the act with an ongoing study of the effects of stress on soldiers' immunity.

But you don't have to wait for the results of the latest wave of immunological research to bolster your own special forces. To keep your immune system running at peak efficiency, here are six proven ways to turn summer fun into solid immunity:

1. Drink iced tea

Classic black tea contains l-theanine; it primes the immune system's gamma-delta T cells to respond five times faster to invading bacteria and viruses. Meanwhile, a compound in green tea called ECGC increases the number of regulatory T cells; they help rev up or tone down immune-system activity. Love herbal tea? Go for chamomile. This relaxing botanical increases blood levels of hippurate and glycine, which aid infection-fighting.

2. Have more fun

Outdoor concerts, hiking, street fairs: Stroll and take in the view: your immune system loves goofing off. Just anticipating something you enjoy bolsters immunity by reducing levels of immune-weakening stress hormones cortisol and epinephrine. And you'll bolster your defenses if you laugh out loud.

3. Enjoy easy exercise

It turns out playful exercise routines that speed up and slow down are kinder to your immune system than hard-charging, steady-paced workouts. Try varying your pace during a morning walk around a garden, an afternoon bike ride by the shore or a swim in the pool. Haul out your tennis racquet (a game where the pace is always changing) or play backyard badminton and kickball with the kids.

4. Have a glass of wine

In moderation, alcohol can enhance immune response and bolster your reaction to vaccines. Not an alcohol drinker? You can get your immune benefit by snacking on fresh berries or grapes, or opt for peanuts at the ballgame, both contain this beneficial compound.

5. Farmer's market

Bumping up your fruit and veggie quotient is a proven way to rev up your immune system and cut down on doctor visits, recent research says. Produce (wash it well) seems to support the activity of infection-fighting T-cells. And the fiber it contains feeds immune-boosting good bacteria in your digestive system.

6. Now, relax

Kicking back in a hammock for some serious R&R is deep-down good for you. It busts stress, which wears down immunity, and then relaxation goes a step further: One recent study found that deep rest switches on genes involved in healthy immune functioning. Yoga, deep breathing and meditation can get you into this zone.

Mehmet Oz, M.D. is host of "The Dr. Oz Show," and Mike Roizen, M.D. is Chief Wellness Officer and Chair of Wellness Institute at Cleveland Clinic.