<P> The h / h blood group, also known as Oh or the Bombay blood group, is a rare blood type . This blood phenotype was first discovered in Bombay, now known as Mumbai, in India, by Dr. Y.M. Bhende in 1952 . </P> <P> The first person found to have the Bombay phenotype had an interesting blood type that reacted to other blood types in a way never seen before . The serum contained antibodies that reacted with all red blood cells' normal ABO phenotypes . The red blood cells appeared to lack all of the ABO blood group antigens and to have an additional antigen that was previously unknown . </P> <P> Individuals with the rare Bombay phenotype (hh) do not express H antigen (also called substance H), the antigen which is present in blood group O. As a result, they cannot make A antigen (also called substance A) or B antigen (substance B) on their red blood cells, whatever alleles they may have of the A and B blood - group genes, because A antigen and B antigen are made from H antigen . For this reason people who have Bombay phenotype can donate red blood cells to any member of the ABO blood group system (unless some other blood factor gene, such as Rh, is incompatible), but they cannot receive blood from any member of the ABO blood group system (which always contains one or more of A, B or H antigens), but only from other people who have Bombay phenotype . </P> <P> Receiving blood which contains an antigen which has never been in the patient's own blood causes an immune reaction due to the immune system of a hypothetical receiver producing immunoglobulins not only against antigen A and B, but also against H antigen . The most common immunoglobulins synthesized are IgM and IgG (and this seems to have a very important role in the low frequency of hemolytic disease of the newborn among non-Bombay offspring of Bombay mothers). </P>

Difference between o blood group and bombay blood group
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