Blood is a vital fluid for the body, primarily comprising of red blood cells, white blood cells, and platelets. It performs critical functions, including transporting oxygen from the lungs to the body’s cells, regulating body temperature and pH levels, and preventing blood loss by promoting wound healing by creating a “plug” to seal the wound. Blood also plays a crucial role in supporting the immune system[1].

Since, blood cannot be manufactured, patients in need for blood or blood related products -such as plasma- rely on blood donations. According to the Red Cross, about 85-million units of red blood cells are donated annually worldwide, and the demand for red blood cells continues to grow[7]. Blood donations save millions of lives each year, allowing for complex medical and surgical interventions and drastically improving the life expectancy and quality of life for patients with acute and chronic conditions[2].

Recently, scientists discovered a group of gut bacteria enzymes with the potential to transform all blood types into universal blood type O. This breakthrough could facilitate blood transfusions in healthcare and save lives[3].

Blood Types and Donor-Recipient Compatibility

Blood is categorised into four main groups: A, B, O and AB, based on the presence of antigens on the surface of red blood cells. These groupings are determined by the presence of A and B antigens, which are substances that can trigger an immune response. When incompatible blood types mix, the antigens cause the cells to clump together in a process called agglutination. Additionally, there is a protein called the Rh factor, which can either be present (+) or absent (-), creating the most common blood types: A+, A-, B+, B-, O+, O-, AB+, AB-)[4].

Here is how it works: individuals do not produce antibodies against their own blood type but will against other antigens. For instance, someone with Type A blood will not generate antibodies against the A antigen but will develop them against the B antigen (Figure 1).

If a person with Type A blood receives a transfusion with type B or AB blood, their antibodies will recognise the foreign B antigens and trigger an immune response. This can lead to a dangerous reaction where the body attacks and destroys the newly introduced blood cells, causing severe complications[5].

Blood Types Explained
Figure 1. Blood Types Explained

Blood Type O- does not have any antigens at its surface, making it a universal donor. It can be given to any other blood type without causing complications, which is why it is in high demand for transfusions, as it can be received by all blood groups[5].

Image from blood.co.uk
Image from blood.co.uk

How Gut Bacteria Could Create Universal Blood

Scientists have been studying enzymes from the human gut microbiome using metagenomics. This technique allows them to sample the genes of millions of microorganisms without needing individual cultures. Researchers used E. coli to select DNA coding for enzymes that can “chop” antigens. They found candidate enzymes in the human gut microbiome. The mucosal lining of the gut is composed with glycosylated proteins known as mucins, which present various sugars, including the A and B antigens.

Certain gut bacteria, specifically Akkermansia muciniphila, can cleave these sugars from mucins and use them as a food source. Upon closer examination, scientists discovered that these bacterial enzymes could selectively remove A and B type sugar antigens from mucins. This means that using these enzymes from the gut microbiome could potentially convert group A and B red blood cells into a universal group O blood (Figure 2)[3][6][7].

Currently, the research is ongoing to test these enzymes on a larger scale for potential clinical applications.

How bacterial enzymes are used to make engineered universal blood
Figure 2. How bacterial enzymes are used to make engineered universal blood

Conclusion

Utilising enzymes from the human gut microbiome presents an innovative solution for enhancing the safety and efficacy of blood transfusions. This approach simplifies blood logistics and addresses critical issues such as blood shortages and the risks associated with mismatched transfusions.

Moreover, this research shows the immense potential within the human gut microbiome. By leveraging the enzymatic capabilities of gut bacteria, scientists are unlocking novel solutions for creating a universal blood supply but also shedding light on the microbiome’s role in understanding and potentially combatting various diseases.

References

  1. https://www.ncbi.nlm.nih.gov/books/NBK279392/
  2. https://www.ncbi.nlm.nih.gov/books/NBK305666/
  3. https://www.nature.com/articles/s41564-024-01663-4
  4. https://www.ncbi.nlm.nih.gov/books/NBK580518/
  5. https://www.hematology.org/education/patients/blood-basics/blood-safety-and-matching
  6. https://www.nature.com/articles/s41564-019-0469-7?fromPaywallRec=true
  7. https://www.jbc.org/article/S0021-9258(17)48329-3/fulltext

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