Your Immune System: A Unique and Ever-Changing Shield

The Adaptive Defender: Your Immune System’s Dynamic Shield

The biggest difference between us isn't how we look, it's our immune systems. And guess what? There's no ranking system there - everyone's distinct. Recent research shows that each person’s immune system is distinct, akin to a fingerprint or DNA.^[9,11] Mapping antibodies from healthy and sick individuals revealed this diversity.

Much of this diversity comes down to our inherited genetic makeup. “The greatest diversity in all of the 25,000 genes that make up the human genome is in our few immune system genes,” Daniel Davis, professor of immunology at Imperial College London and author of The Compatibility Gene, explains. “That means that the genes that vary most between us all are the ones that influence the immune system.”^[1]

Researchers used a special model to study differences in immune cell types among mice.^[9] They pinpointed genes that control the number of each immune cell type, many of which work within their own cell type to regulate growth, movement, and death. Interestingly, they also found a unique set of genes expressed in one immune cell type that control another. 

By analyzing genomes across various vertebrates, the researchers discovered that these "crosstalk" genes have accumulated more mutations. This suggests that these genes provide a safe zone for evolution to experiment, allowing for the creation of new interactions between cell types without harming the organism. This increased diversity could be key to the immune system's ability to adapt to new threats.

Figure 1. Cellular and Molecular Mechanisms Underlying Trained Innate Immunity (details) 

Individuality in Immunity: Why We Fight Disease Differently

While some people seem to breeze through infections, others struggle. Here's why:

• Early exposure and vaccination: People with a history of encountering germs and receiving vaccinations may have a primed immune system.
• Inherited immune differences: Every individual’s immune system is naturally tuned to combat certain illnesses more effectively. 
• Genetic variations in HLA genes shape pathogen recognition, a phenomenon supported by research such as the 2018 Nature Genetics study on HLA and disease susceptibility.
• HLA variations can also confer disadvantages—e.g., HLA-B*27 is protective against some viral infections but increases the risk of autoimmune diseases like ankylosing spondylitis.
• Dietary influence: A healthy diet supports a robust immune response.
• Viruses as Immune Catalysts: Viruses help educate the immune system by triggering memory cell creation, enhancing future defenses—a process central to immunity from natural exposure or vaccines. Some scientists suggest viruses have evolutionarily refined human immunity, but not all are beneficial, with dangerous exceptions like HIV and Ebola.
• An orchestra of immunity: While colds can signal a hardworking defense system, frequent or severe bouts may hint at an underlying immune dysfunction.

Beyond "Superhuman" Immunity:

The concept of a universally "stronger" immune system is misleading. The incredible diversity of our immune systems makes such generalizations meaningless. Doctors focus on understanding how the innate and acquired immune systems work together to fight infection.

Lifestyle choices also significantly impact our immune response:

• Stress: Chronic long-term stress can suppress immune function by producing cortisol, which weakens immune cells.
• Sleep: Sleep is crucial for immune health. Disrupted sleep patterns can throw off your immune system's natural rhythm.

The Gut Connection:

Adding another layer to this complexity is the gut microbiome, consisting of trillions of bacteria that directly influence the immune system. A healthy gut microbiome packed with diverse bacteria contributes to a strong immune response.

Our Unique Fingerprint: The Power of Diversity

In summary, our immune systems are:

• Highly individual and complex: Like fingerprints, no two immune systems are exactly alike.
• Rapidly evolving: The genes controlling our immune system are the most diverse in our entire genome, allowing for quick adaptation to new threats.
• Diverse in function: This variation enables our species to combat a wide range of illnesses.
• Shaped by genetics: Our unique immune response is partly determined by our inherited genes.

Understanding this diversity is key to appreciating the remarkable power of our immune system.

References

1. The secrets of people who never get sick
2. Coronavirus—What Makes Some Patients Sicker than Others?
3. Why women live longer than men?
4. Natural Immunity
5. Why is Covid-19 more dangerous for older people?
6. SARS‐CoV‐2 re‐infection risk in Austria
7. How to keep your immune system strong?  
8. COVID-19 vaccines may trigger superimmunity in people who had SARS long ago
9. Interactions between immune cell types facilitate the evolution of immune traits
10. Study sheds light on the immune system's evolution
11. Our immune system is as unique as a fingerprint or our DNA