The genetic lottery: self-destruction or survival?

Illustrated strand of DNA

As one of the many scientists who contributed to our Settlers exhibition, geneticist Dr Calliope Dendrou from the Wellcome Centre for Human Genetics ran a Spotlight talk as part of the exhibition’s event programme, where she explained more about her research into genetics and autoimmune diseases…

Our genes make us who we are – they are what unite us a single species, Homo sapiens – but they are also what make us unique individuals, with a particular set of characteristics. Genes are made up of DNA inherited from one individual to the next, transmitting the code for life through time.

The DNA ‘alphabet’ comprises four letters, A, C, G and T, and three billion of these letters make up the complete human genome. Comparing two unrelated individuals, on average around one in 1,000 of the three billion letters will differ. Genetically speaking, each of us is 99.9 percent the same as every other unrelated person.

Studying our genetic composition and the similarities and differences between individuals is of interest from a historical, geographic and sociological perspective, as the Settlers exhibition at the Museum shows. But it can also have medical implications for our understanding of the types of diseases we are susceptible to.

1024px-Neutrophil_with_anthrax_copy

Immune cell (yellow) engulfing anthrax bacteria (orange). Image: Volker Brinkmann [CC BY 2.5], via Wikimedia Commons

My lab works on the genetics of autoimmune diseases, which affect some ten percent of people worldwide and include relatively common conditions such as rheumatoid arthritis, multiple sclerosis, and type 1 diabetes.

Autoimmune diseases arise when the cells of the immune system function inappropriately. The immune system is made up of millions of immune cells patrolling the body, sensing their environment and sending signals to each other.

If the body has been injured due to physical trauma or an infection, then upon receiving the right signals immune cells help to clear damaged cells or fight off pathogens. But sometimes immune cells can begin to respond to the wrong signals, triggering a self-destruction. When this happens they can destroy the body’s own tissues and organs and then autoimmune start to diseases develop.

Auto immune illustration

Autoimmune disorders in a nutshell –  illustration by Beatrice the Biologist

The common autoimmune diseases are very complex and are thought to result from a combination of genetic and environmental influences. Hundreds of genetic factors can influence someone’s risk of autoimmune disease development, so having a low or high risk is a genetic lottery – it depends on how many different genetic factors happened to have come together for that person.

We are investigating the biological consequences of these genetic factors to find better ways to target the immune cells that are attacking the body. The trick is to do this without suppressing the immune system’s ability to fight off infection, a problem associated with drugs used treat autoimmune disease patients today.

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