Proline supplementation stimulates immune system
If you're suffering from flu, or youve just had a vaccination against a nasty bacteria or unpleasant virus, then supplementation with the amino acid proline [structural formula shown here] can give your immune system a boost. At least, that's what you'd expect after reading the results of the animal study by scientists at the Chinese ministry of agriculture published in Amino Acids.Proline & vaccination
Proline is not an essential amino acid. It is found in gelatin, but your body also makes it by converting L-ornithine. Nevertheless, proline is an important amino acid. It plays a key role in the healing of wounds and the functioning of the immune system. The latter aspect caught the attention of the Chinese.

Vaccines often contain small quantities of aluminium hydroxide. This compound makes vaccines more effective, but also inhibits immune cells. There must be a better way doing things, the Chinese thought - so they went in search of an alternative. They hope they've found this in the form of proline.

The Chinese performed experiments with mice. The mice were injected with a vaccine against the bacteria Pasteurella multocida. A control group were given no vaccine [Control].The first group of vaccinated mice were given two injections containing a vaccine only [V-O]; the second group were given a vaccine with aluminium hydroxide [V-H]. The third group were given food that had been enriched with the amino acid L-alanine for a month [V-A], and a vaccine without aluminium hydroxide. The fourth group was given food for a month that contained 0.4 percent L-proline, and a vaccine without aluminium hydroxide. The Chinese used L-proline produced by Ajinomoto.
At the end of the month the Chinese injected the lab animals with Pasteurella multocida. Two days later all mice in the Control group were dead.

The mice that had had a vaccine that contained aluminium hydroxide [V-H] all survived. Not all mice in the V-A and the V-O group survived. But the mice that had been given proline in their food, and had had vaccines without aluminium hydroxide, all survived too.

The researchers were not able to uncover exactly how proline helps the immune system to work better. They did see slightly higher levels of antibodies in the blood of the proline mice than in the blood of the animals in the V-A and V-O groups.

"To our knowledge, this is the first study to determine the adjuvant effect of proline in mammals", the researchers write. "Our findings have important implications for preventive medicine in humans and animals."

So doing a quick calculation: a mouse eats about 4 g food per day. If the diet consists of 0.4 percent L-proline, that works out at 16 mg proline. The mice weighed 20 g. Per kg bodyweight they therefore ate 800 mg proline.
Converted to humans, that means 80 mg per kg bodyweight. So if you weigh 80 kg you would need about 6 g proline per day to stimulate your immune system.
Amino Acids. 2013 Sep;45(3):555-61.