In a bizarre case, an American multi-millionaire in his 40s is attempting to reverse ageing using blood plasma transfusions from his teenage son, media reports said.

With the blood plasma transfusions from his 17-year old son, Bryan Johnson, 45, claims to have the skin of a 28-year-old and the lung capacity of an 18-year-old, the Sun reported.

Previously, he received blood transfusions from healthy, anonymous donors who were carefully screened to ensure they had an ideal body mass index and were free of diseases.

In the process, one litre of blood from each participant is removed and converted into liquid plasma, red blood cells, white blood cells, and platelets via a high-tech machine.

It is then injected into Johnson's veins which he believes will rejuvenate and repair his old blood and keep him looking and feeling young, the report said.

The American tech mogul also recruited his dad Richard, 70, to join him in the tri-generational blood product exchange.

"My son, father and I completed the world's first multi-generational plasma exchange," Johnson wrote on Instagram.

On the social media app, he also documented the bizarre process of transfusion, undertaken last month at a medical spa in Texas, US.

The image shows Johnson, and his son Talmage topless, while holding a vial of blood.

Talmage had a litre of blood removed - around one-fifth of the blood in his body, the report said.

Johnson donated a litre of his blood to Richard, while Talmage didn't take any blood from his dad or grandfather, it added.

"One divided by the mind, now united by biology," he wrote on Instagram.

Johnson is an entrepreneur, venture capitalist, writer and author. He is also the founder and CEO of Kernel. (IANS/NS)