This may occur during pregnancy or if a person accidentally receives incompatible blood during a transfusion. The main complication relating to Rh factors involves those who are Rh-negative encountering Rh-positive blood and producing anti-D antibodies in response. However, it can influence their compatibility with other blood types, affecting the type of blood they can receive. While being Rh-positive is more common, being Rh-negative does not indicate illness, and it does not usually affect a person’s health. The positive or negative sign next to the ABO grouping refers to the Rh status and whether the RhD antigen is present or not. Combining these systems creates the eight most common blood types: People with no A or B antigens on the surface of their RBCs have blood type O. The absence or presence of A or B antigens and Rh factor can help classify blood types. RBCs contain proteins, or antigens, on their surface that allow specialists to determine blood types. Although Rh status can vary among populations, roughly 85% of people in the United States are Rh-positive. People inherit their Rh status from their parents, separate from their ABO blood type. The Rh D antigen is the most immunogenic, meaning that it may provoke an immune response. There are five main Rh antigens on RBCs, of which the most important is the Rh D antigen. The Rh factor is an inherited protein that can be present on the surface of RBCs. Whatever its exact role, the new results may help scientists to understand Rhesus-deficiency syndrome, a disease in which either RhCE or RhAG are mutated.Share on Pinterest Yothin Sanchai/EyeEm/Getty Images Or maybe ammonium serves as a signaling molecule and the transporter controls the signal. In humans, ammonium is mainly a waste product and becomes toxic at high blood concentrations, so perhaps RhAG serves to help red blood cells take up ammonium from the plasma and transport it to detoxifying organs, such as the liver or kidney. The scientists obtained similar results for RhGK, a new Rhesus protein found only in liver cells. Furthermore, RhAG was able to provide transportation in the opposite direction: it pumped toxic methylammonium as well as excess ammonium out of the cells. And indeed the yeast cells survived under conditions when they needed to take up ammonium from the environment. To test whether RhAG had the same function in humans, they produced the human protein in mutant yeast cells lacking their own ammonium transporters. The researchers found that RhAG is similar in amino acid sequence to a family of ammonium (NH4+) transporters not found in vertebrates.
The Rhesus factor consists of several parts, RhD, RhCE and RhAG, and only RhD is missing in Rhesus-negative individuals. In todays issue of Nature Genetics, however, scientists from Belgium, France and Italy report that one of its components, RhAG, transports ammonium ions through the cell membrane. Until now, no one knew the function of the Rhesus factor, which was named after a cross-reacting protein in rhesus monkeys. Problems can also arise if a Rhesus-negative mother is pregnant with a Rhesus-positive second child. About 85 percent of the population is Rhesus-positive, sometimes making it difficult for Rhesus-negative people in need of transfusions to find a match. Both are antigens expressed on the surface of red blood cells-and if they are different, they can invoke an immune attack. To avoid complications from a blood transfusion, recipients must be sure a donors blood matches their own, meaning two main factors must agree: the blood group (A, B or 0) and the Rhesus factor, either positive or negative.
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