I am looking for nutrients that directly enhance immunity.
The immune system protects the body from disease.
It is believed that micronutrients support the immune system: specifically, vitamins, minerals and "related cofactors."
Vitamin A, which is a fat-soluble vitamin, appears to be essential in producing stronger immunity. Retinol provides malnourished children with a stronger defense against measles and other viral-related illnesses. Vitamin A also:
...enhances white blood cell function, enhances resistance to infection and carcinogens, and helps maintain skin and mucus membrane defenses to infection.
Carotenoids and beta-carotene have "unique immune-stimulating properties that Vitamin A does not." Beta-carotene is a strong anti-oxidant. In nature alone, there are 600 carotenoids that are highly effective in preventing cancer.
B vitamins are important. They appear to be very effective in fighting the progression of the AIDS virus in patients.
Vitamin C boosts the immune system. It is "an antiviral and anticancer nutrient."
Other immune-enhancing elements are: chromium, copper, iron (working like Vitamin E), manganese, selenium and zinc. There are also other supplements that are non-vitamin and mineral in nature, but those listed above are nutrients that boost the immune system.