Is the immune system ‘selfish’? – a Dawkins perspective

Evolution and Dawkins’ perspective

Charles Darwin introduced the unprecedented theory of evolution by natural selection in his famous work ‘On the Origin of Species’, published in 1859. Gregor Mendel, who explained the concept of Mendelian genetics (the inheritance of genes), was a contemporary of Darwin, but his research was recognised much later on, beyond his time. In the 20^th century, the Modern Evolutionary Synthesis was formed and gave a foundation for how biological life has formed as we see it today.

The Modern Evolutionary Synthesis is widely accepted and strongly supported by experimental and observational evidence across an array of life. Human beings have even leveraged these concepts for hundreds of years through artificial selection, imposing our own sometimes superficial selective pressures on organisms to express characteristics that we desire (such as the case of the Belgian Blue cattle, with a mutation in the myostatin gene making it a muscular, lean beef, or perhaps artificial selection in dog breeding).

Richard Dawkins’ breakout book, ‘The Selfish Gene’, published in 1976, took him from an unknown voice at the University of Oxford passionate about the works of evolution across all animals, to a lauded voice in the scientific community. His concept of genes being selfish is the idea that natural selection works at the gene level, whereby genes over time become better at replication, with the organism acting as a ‘survival machine’ built to help genes propagate. It is important to note that the term ‘selfish’ is not meant metaphysically or philosophically. Figure 1 explains what ‘selfish’ means.

Taking this further, it can be argued that genes helping organisms resist pathogenic attack are more likely to survive and propagate. This means the immune system does not exist to protect the body holistically but rather to protect its genes individually. 

The immune system evolved through the gene-centric lens

As previously mentioned, the immune system has become integral to all complex organisms responding to pathogens as a selective pressure.  Those genes that have conferred a greater ability to combat or resist a particular pathogen allow the organism an improved survival chance until reproductive age has been achieved. The window whereby the organism has reached reproductive maturity and is reproducing is what the genes have been selected to get, which is why many genetic pathways end up becoming detrimental to an organism in old age (explained by the antagonistic pleiotropy hypothesis- APT- and the disposable soma theory). This remains especially true for the immune system.

One must also understand that only vertebrates are biologically equipped with an adaptive immune system (allowing for memory and effective response to previous pathogens), with Figure 2 explaining this difference. This supports that the immune system is a ‘selfish system’, as while many organisms survive without adaptive immunity, more complex organisms have evolved to include it because of our prolonged individual survival and delay in reproductive maturity (indicating that survivability until our reproductive window is an intense selective pressure). 

Immune imperfection through the ‘Selfish System’ lens

We now understand there is a compelling point to be made that the immune system has evolved with the reproductive window in mind and to allow as much gene propagation in a population as possible. If we accept this point of view, it explains many of the trade-offs and imperfections of the immune system when we look at the potential harm caused by immunity.

Allergies are one such example, whereby hypersensitivity causes an immune response to harmless substances, which, through the gene-centric lens, may have evolved to detect pathogens such as parasites. This further supports the ‘selfish system’ idea as reproductive success on a population scale is not impaired by a significant amount by allergies. One such study showed that women with allergies and asthma, despite having systemic inflammation, did not have a reduced fertility rate when analysing the relationship between an increase in allergic diseases in the 20^th century and a decrease in fertility globally. 

Chronic inflammation through persistent immune activation in old age (a concept termed inflammaging) is another such example. We previously mentioned that past reproductive age natural selection weakens, meaning that our genes are selected for early life immune optimisation, even if that means they cause problems later in old age. Processes such as cellular senescence, inflammasome activation, oxidative stress, immune cell dysregulation and so on begin to occur, leading to an increased risk of age-related diseases such as cardiovascular disease, cancer, dementia, sarcopenia and so on. 

Immune evolution is therefore a ‘selfish system’ because it seems to care more about gene propagation in the young to middle-aged years in comparison to long-term organism health, as many immune systems rapidly decline and become detrimental.

Conclusion

This perspective of the immune system as a ‘selfish system’ allows us to understand that it is not a protector of the organism throughout its life span, as we may perceive it to be, but rather that it is a mechanism evolved and optimised to propagate genetic material during the organism’s reproductive window (expanding beyond humans). This analysis of the immune system through Richard Dawkins' lens of the “selfish gene” helps us to understand many of the limitations of the immune system. 

Working on treatments to preserve and maintain the immune system’s healthy state, which reflects young adult life, appears to be a promising approach for future clinical prevention plans for old age diseases. There are many currently being researched and emerging treatments with this principle in mind, such as senotherapeutics and mTOR inhibitors (such as rapamycin and other rapalogs), making this an interesting field to keep up to date with. 

Written by Yaseen Ahmad

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