Ancient DNA Helps Our Immune System Fight New Threats

The remains of ancient viruses in our genetic history help B cells fight new and unknown infections.

The human immune system is an incredibly well coordinated concert of destruction. From what we understand so far, a person’s ability to fight off new and unknown infections follows a well choreographed flow.

We’ve all heard of white blood cells (WBCs), the cells that form the core of our immune system. This population of cells is actually divided into different types of WBCs. There are colonies of ‘intelligence gathering’ cells called T cells which study and try to understand invading viruses and bacteria. They present this information to their close cousins, the B cells.

The B cells use the clues passed on from their cousins and fabricate any of the vast array of toxic substances called antibodies. These antibodies stick to the targets and tag them for destruction.

The story doesn’t end there. A small portion of these Primed B cells then undergo a change in their genetic structure and ‘hard code’ the antibodies used to destroy their most recent opponent. They become ‘memory cells’ and linger in circulation as sentries and caches of information needed to fight off any invasion from their defeated foes.

These systems are complex and exquisitely tuned to be able to create the ultimate magic bullet for a specific infection and retain the information to make that magic bullet in the future if the need arises. The process takes time though and a lot of modern medicine is based on supporting the body while this vital intelligence and fabrication process is ramped up.

As we have understood it for decades, B cells can’t really function without T cells. They need the ‘intelligence’ of the T cells. However, that doesn’t square with recent observations.

Over the decades, as molecular biology has advanced, research has found that, occasionally, B cells can start the antibody production process without the help of their T cell intelligence brethren.

This leads to quicker reaction time and sometimes, enhances the ability to stop an infection before it gets out of hand.
It turns out; there are pieces of ancient DNA in us. DNA from viruses that our forefathers fought off and killed generations ago. That DNA is useful to us now. Researchers call these ancient strands of DNA ‘Endogenous Retroviruses’. That’s a fancy term for viral coding that is within our own human genome.

Just think of the population in Liberia and Sierra Leone, how they fought Ebola and still register lesser deaths than the number of deaths that Ebola has caused in other countries. It is because the previous generations of Liberia have fought against it and their T cells have the intelligence to teach the B cells to prepare antibodies. The present population in those regions have inherited the coded DNA of their previous generations and are prepared to fight the virus better whereas the people in Europe and the US do not have them and thus, are more likely to succumb to death.

These pieces of ancient DNA (endogenous retroviruses) were first identified in studies on mice. The endogenous retroviruses are almost like museum pieces inside our DNA. They are old pieces of code that the B cells can use to formulate new antibodies.

We still don’t know for sure, how these endogenous retroviruses actually incorporate themselves into our DNA.
Many viruses in nature tend to incorporate themselves into our DNA on purpose. They inject their DNA or RNA into our living cells and get themselves written into our code. The aim is to hijack our cells’ machinery, to replicate them and perpetually keep the infection at bay.

It could be that process of ‘writing in’ which is what is ultimately being used against future viruses.
When an old virus writes its code into our DNA, our DNA uses that code to fight it in the future.