Like everything else in our bodies, the immune system depends on nutrients to function properly. According to a paper by Simin N. Meydani, PhD, a professor at the Friedman School and director of the Nutritional Immunology Laboratory at the Human Nutrition Research Center on Aging, and her colleagues, mounting evidence suggests ensuring you get adeqate amounts of certain nutrients may help optimize immune function, including improving resistance to infection. Here is what we know so far:
Vitamin E is an antioxidant that protects cells, including immune cells, from oxidative damage. Evidence suggests vitamin E supports optimal immune function. While vitamin E supplementation can increase risk for bleeding and stroke, dietary intake is perfectly safe.
Vitamin E is found naturally in foods like plant oils (especially sunflower, safflower, and wheat germ oil), nuts, and seeds. This vitamin is sometimes added to processed foods like breakfast cereals (check Nutrition Facts labels). Green vegetables, such as spinach and broccoli, also provide some vitamin E.
Vitamin D receptors are found in most immune cells. Adequate vitamin D levels may help maintain the body’s defense against infection.
Yogurt, yogurt everywhere! 
Wellness Secrets of a SuperAger 