Human Blood Groups
This chart lists the antigens and antibodies made by the different ABO blood types. Clearly, people who are type O— the most common blood type —do just fine without them. What scientists have found in the last century, however, are some interesting associations between blood types and disease. People who are type A, for instance, seem more susceptible to smallpox, while people who are type B appear more affected by some E. Over the last hundred years, scientists have also discovered that the ABO blood group is just one of more than 20 human blood groups.
The Rh refers to Rhesus macaques , which were used in early studies of the blood group. Most people have never heard of the numerous other blood groups—such as the MN , Diego , Kidd and Kell —probably because they trigger smaller or less frequent immune reactions. People who lack the Duffy antigens, therefore, tend to be immune to this form of malaria.
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World Population By Percentage of Blood Types
New Research. Curators' Corner. Ask Smithsonian. Photos Submit to Our Contest. ABO Blood type antigens are not only found on the surface of red cells. They are also normally secreted by some people in their body fluids, including saliva, tears, and urine. Whether someone is able to secrete them is genetically controlled.
Police agencies now routinely use this so-called secretor system data to identify potential victims and criminals when blood samples are not available.
What makes a blood type?
Despite the fact that the blood types of children are solely determined by inheritance from their parents, paternity in the U. Antibodies to alien antigens in the ABO group are usually present in our plasma prior to the first contact with blood of a different ABO type. This may be partly explained by the fact that these antigens are also produced by certain bacteria and possibly some plants.
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When we come in contact with them, our bodies may develop long-term active immunity to their antigens and subsequently to the same antigens on the surface of red blood cells. This usually occurs in babies within the first six months following their birth. Environmental Factors. It does this through natural selection. Specific ABO blood types are thought to be linked with increased or decreased susceptibility to particular diseases.
For instance, individuals with type A blood are at a somewhat higher risk of contracting smallpox and developing cancer of the esophagus, pancreas, and stomach. People who are type O are at a higher risk for contracting cholera and plague as well as developing duodenal and peptic ulcers. Research suggests that they are also more tasty to mosquitoes. That could be a significant factor in contracting malaria.
They are not simply AB codominant. Apparently, most of these blood chimera individuals shared a blood supply with their non-identical twin before birth.
In some cases, people are unaware that they had a twin because he or she died early in gestation and was spontaneously aborted. Some people are microchimeric--they have a small amount of blood of a different type in their system that has persisted from a blood transfusion or passed across the placental barrier from their mother before birth.
Likewise, fetal blood can pass into a mother's system. This fact has led some researchers to suggest that the significantly higher frequency of autoimmune disorders in women is a result of the presence of foreign white blood cells that had come from their unborn children during pregnancy. This has the potential for dramatically improving the safety of blood transfusions. Clinical trials of this technique are now underway. They refer to them as enterotypes. This type system is independent of blood types and may have equally important implications for peoples' health.
How enterotypes are established is not known, but the authors suggest that babies may be randomly colonized by different species of bacteria and that they alter the gut so that only certain species of bacteria can live there. All rights reserved.
Illustration credits. The possible ABO alleles for one parent are in the top row and the alleles of the other are in the left column. Offspring genotypes are shown in black. Phenotypes are red. Bombay Phenotype. AB AB. Previous Topic. Return to Menu.