From the Manufacturer:
Immune System Defense is carefully balanced with powerful immune enhancers. Its combination improves general health, fights infections and allows the body to deal with stress more effectively. Immune System Defense is a revolutionary formula, bringing the most widely used immune boosters into a single formula. This formula is great for teachers, health care workers and others who are always around groups of people with colds or other illnesses.
Everyone has heard that Vitamin C is great for helping the body fight off colds. Stress can greatly reduce the amount of vitamin C your body has available which in turn results in a weakened immune system. Vitamin C increases white blood cell production and is important to immune system balance. Ester-C is a specialized form of Vitamin C, which is more easily absorbed by the body and less likely to cause stomach irritation.