A protective damage
Thalassemia is a genetic damage to the hemoglobin in the blood. A special form of this disease occurs primarily in malaria areas. The reason for the increased prevalence in these regions appears to be that the damage also serves as protection against most types of malaria. New research shows that children affected by thalassemia are also less susceptible to other infections. The function of normal human red blood cells is to carry oxygen from the lungs to the other organs in the body. Each red blot cell contains millions of molecules of hemoglobin, the oxygen-carrying protein. It consists of an iron-containing heme molecule and two pairs of protein chains - alpha and beta globin. In alpha+ thalassemia, certain genes that control the synthesis of alpha-globin chains are absent. Each parent inherits one gene to the child. If only one of the two responsible genes is not present, no symptoms can be identified. If both genes are missing, the affected person develops symptoms of the disease in the form of mild anaemia.
Having thalassemia is known to concomitantly protect against malaria to some extent. For this reason, such damage in malaria areas even represents a positive selection factor that is passed on to the offspring accordingly.
Two studies have shown that children suffering from alpha-thalassemia are more susceptible to mild forms of malaria. As a result, they are likely to be more protected against infection with more serious types of malaria later in life. S. J. Allen of the University of Oxford and his colleagues at the Papua New Guinea Institute of Medical Research conducted a larger study in a hospital on the north coast of Papua New Guinea (Proceedings of the National Academy of Sciences, 23rd edition). December 1997). Alpha thalassemia affects more than 90 percent of the population in this region.
The results of the study confirmed the prevailing theory: children who did not have alpha-thalassemia were about 1.5 times more likely to develop severe malaria than children who had only one alpha-globin gene present, and 2, 5 times more common than those lacking both alpha globin genes.
But the investigation showed another, unexpected result. Not only does alpha-thalassemia reduce susceptibility to malaria, but also susceptibility to infection with other common childhood diseases. Examples are gastrointestinal inflammation, respiratory diseases and meningitis. What the protection is based on is not yet clear. The scientists suspect that as a result of alpha-thalassemia, certain parts of the immune system may be more active than in he althy children. In fact, the disease appears to be an important factor in child survival in Papua New Guinea.
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