The Rhesus system was simultaneously discovered in 1937 by Levine and Stester and in 1940 by Karl Landsteiner and Alexander S. Wiener. Levine and Stetser discovered the actual D antigen, and Landsteiner and Wiener discovered the anti-D antibody.
You don't have to have Rh negative parents to be an rh negative blood type. Two people who are rh positive can have an rh negative baby. This is because the rh protein is considered to be a recessive allele, just like the blood type O. Your rh positive parents can each be what is called Heterozygous, which means they carry one rh negative allele and one rh positive allele. If both parents provide a copy of the rh negative allele, then the child will be rh negative, because they have two negative alleles. If one parent donates an rh negative allele, and the other parent donates an rh positive allele, then the child will be rh positive- because the rh positive alleles are dominant.
The following example illustrates the point. The left hand cell is fully rh positive, the middle cell has noticably less D (+) proteins- so that cell is considered to be weak D. A person with "weak D" blood is +/-. The cell on the right shows a blood cell with no D proteins, it is Rh negative.
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Because of the specificity of blood types, it's important to note that a negative reaction can occur when ANY two "un-matched" blood types are mixed- it's not just rh negatives that are in danger of this. However, when an rh D negative produces antibodies to rh positive blood, it's a particularly potent antibody and can cause very serious problems during transfusions or pregnancy.
The percentage of Rh (D) negative blood varies within ethnic groups, and is most commonly found in Caucasian peoples of European descent. The following is a breakdown of occurrence in some ethic and racial groups.
Rates of Rh negative blood among ethnic and racial groups
- White - 15-16%
- African American - 8%
- African - 4%
- Basque (region of Spain/France) - 30-35%
- Asian - Less than 1%
- Asian American - 1%
- American Indian/Inuit - 1-2%
- Eurasian - 2-4%
According to Dr. Luigi Cavalli-Sforza the highest percentage of rh negative blood is in the tribes still living in the Atlas mountains, the next highest are the Basque.
In a transfusion situation, an rh (D) negative individual, should receive only A-B-O compatible rh negative blood because an rh negative body will not recognize the positive rh (D) proteins (or antigens) as SELF and will attack even an A-B-O compatible blood type if it has the additional (D) protein (antigen). Unfortunately, the availability of rh negative blood is limited by eligible, available donors and some areas of the world just don’t have much of it! In cases where no rh negative blood can be found, then the compatible rh positive blood type will be used. It’s always a good idea for rh negatives to bank their own blood, and/or have a contact list of people who could donate to you if you ever need it.
When an rh negative does not develop antibodies to rh positive blood, it’s called Sensibiliation. There has been no research done to determine why some rh negatives become sensitized and others do not.Alloimmunization or sensitization refers to the immune process that occurs when the rh negative body reacts to rh positive blood. The process of
Alloimmunization or sensitization is a simple immune response where the body detects something that is not SELF, and sends antibodies to fight it. The amount of blood exposure that causes alloimmunization varies. Some rh negative people have developed antibodies to as little 0.01 ml. of rh positive blood. There are others, (about 30% of rh negative people) who will NEVER develop an immune response, even when challenged with large amounts of rh positive blood and or repeated exposure.
50% of rh negative people who have developed antibodies will naturally purge them from their body. The antibodies do not cause personal physical harm to the rh negative individual, and only becomes a problem in a transfusion situation, or pregnancy with an rh positive child.
When alloimmunization occurs, the body produces antibodies which attach themselves to the offending antigens and essentially suffocate them. This is called Hemolysis. The process of hemolysis is called a hemolytic reaction.
In pregnancy, a hemolytic reaction in the fetus is called Hemolytic Disease of the Newborn, and can occur with any difference in the Rhesus System proteins. However, a reaction to the Rh (D) proteins is considered the most severe form of Hemolytic Disease of the Newborn and is commonly referred to as Rh Disease. Symptoms range from mild to severe and can include anaemia and heart failure.
Thanks to: http://rhnegativeblood.ning.com