We all know that malaria parasites evade the human immune system while living in human red blood cells. A good news is that according to a new study, blood type O provides protection against malaria.

The study suggests that a protein secreted by parasites called RIFIN, plays an important role in providing protection against malaria in people who have blood group O.

A team of Scandinavian scientists explains the mechanisms behind the protection that blood type O provides and suggests that the selective pressure imposed by malaria may contribute to the variable global distribution of ABO blood groups in the human population.

It has long been known that people with blood type O are protected against severe malaria, while those with other types, such as A, often fall into a coma and die. Unpacking the mechanisms behind this has been one of the main goals of malaria research.

Scientists led from Karolinska Institutet in Sweden have now identified a new and important piece of the puzzle by describing the key part played by the RIFIN protein.

Using data from different kinds of experiment on cell cultures and animals, they show how the Plasmodium falciparum parasite secretes RIFIN, and how the protein makes its way to the surface of the blood cell, where it acts like glue. The team also demonstrates how it bonds strongly with the surface of type A blood cells, but only weakly to type O.

Principal investigator Mats Wahlgren describes the finding as conceptually simple, however, since RIFIN is found in many different variants, it has taken the research team a lot of time to isolate exactly which variant is responsible for this mechanism.

Wahlgren said that their study ties together previous findings, adding they can explain the mechanism behind the protection that blood group O provides against severe malaria, which can, in turn, explain why the blood type is so common in the areas where malaria is common.

Wahlgren added that in Nigeria, for instance, more than half of the population belongs to blood group O, which protects against malaria.

The study was published in Nature Medicine.