Taurine is critical for cats. Arginine, another amino acid found in meat protein, is also important for cats. Arginine is important for heart function, the pancreas, and for keeping the gut healthy, in addition to its detoxification role. Cats also need animal fat. Unlike humans, they must have animal fat as a source of fatty acid.
Arachidonic acid is particularly important for feline immunity.
Restoring this important fatty acid may enhance longevity in the FeLv-infected cat. Vitamin A is another nutrient cats must get from their diet. They do, however, use beta-carotene. However, some research indicates that beta carotene protects lymphocytes from radiation and preserves the natural antioxidant, glutathione. It's very likely that in cats and dogs beta-carotene is also being used to protect and enhance immunity.