Bombay Blood Group

Rare blood donor registry; need of the hour

Shardul Nautiyal - Mumbai

Reena Mathews lost blood heavily during delivery and urgently required blood. A sample of her blood was sent to the blood bank for matching. The red cells grouped like O group, while her serum reacted with all O group cells available in the blood bank during cross-matching or compatibility test, making the blood bank official realise that the lady may be carrying the rare Bombay Blood group.

Experts inform that a rare genotype (blood group) of people was detected in Mumbai, a few decades back, who neither had A, AB, B or O group. This rare genotype was labelled as the Bombay Blood Group. If a Bombay Blood Group recipient is not transfused the blood of a Bombay Blood Group person, it can lead to a haemolytic transfusion reaction, which can be fatal and lead to death.

According to Dr Anand Deshpande, consultant, transfusion medicine and haematology, Hinduja Hospital, “Transfusion of ‘O’ group blood to these persons would result in immediate red cell lysis because of the presence of anti H antibodies in the serum of Bombay Blood Group patients. Therefore blood from only a Bombay Blood Group individual should be transfused to a Bombay Blood Group recipient.”

Studies reveal that this is due to the absence of the H substance (antigen) in the red cells. The absence of the H substance is attributed to the deficiency of the enzyme fucosyl transferase. The Bombay Blood Group phenotypes lack H antigen in the red cells and have anti-H in the serum.

Says Dr Maya Parihar Malhotra, blood bank in-charge, Bombay Hospital, “Family studies have shown that the Bombay phenotype, called as Oh, is due to the presence in homozygous state of a rare recessive gene.”

The precursor protein from which the blood group proteins are formed is termed as the H substance. This is bio-chemically produced by the binding of Fucose to the surface glycoproteins, the process being catalysed by Fucosyl transferase. If N-acetyl galactosamine binds to the H substance, it forms the blood group A, whereas if galactose binds to it, it forms the group B. Absence of any binding substance produces the O blood group.

Studies reveal that all human red blood cells with exceedingly rare exceptions carry the red cell H antigen. It is present in greatest amount on type O red cells and least on type A1B cells. The H antigen is an intermediate stage in the production of the A and B antigens. The individuals with the so-called Bombay phenotype are recognised with the presence of anti-H in the serum, in addition to anti-A and anti-B, as in type O persons.

Experts say that if proper blood grouping or testing practices is not followed, it can lead to people with Bombay blood group not being detected. According to Dr Mukesh Desai, haematologist, H N Hospital, “During cell grouping or routine grouping, Bombay Blood Group would be categorised as O group because they wouldn’t show any reaction to anti-A and anti-B antibodies just like a normal O group. When a cross matching with different blood bags of O group is done, then it would show cross-reactivity or incompatibility. Therefore Reverse grouping or Serum grouping has to be performed to detect the Bombay Blood group.”

“Other issues related to Bombay Blood Group is that blood is incompatible with all A, B and O donors. In routine forward grouping, this blood group would give reaction as an ’O’ blood group where as in serum grouping it would show reaction with ’O’ cells due to the presence of anti H in their serum,” says Dr Deshpande.

Most of the cases once detected are registered at Institute of Immuno-haematology (IIH)) for further studies as well as for availability of information regarding the donors of this group.

According to Dr Kanjaksha Ghosh, deputy director, IIH, “Since Bombay Blood Group is the rarest of the rare group, it is desirable to develop cryopreservation facilities for rare donor units. Every blood bank can easily maintain a rare blood type donor file from amongst their regular voluntary donors.”

“If these blood banks can borrow or exchange rare blood units in times of need, lot of problems related to rare blood groups like Bombay Blood Group can be solved. This is only possible if each blood bank has a large number of committed regular voluntary donors,” added Dr Ghosh.

“The wrong notion among people need to be dispelled that of the possibility of getting infections like HIV1 through blood donation. The public need to be informed that there is no way a donor can get such infection through blood donation,” opined Dr Ghosh.

Cell Grouping			Serum Grouping			Interpretation
Anti A	Anti B	Anti AB	A cells	B cells	O cells
+	-	+	-	+	-	A
-	+	+	+	-	-	B
+	+	+	-	-	-	AB
-	-	-	+	+	-	O
-	-	-	+	+	+	Bombay Blood Group

Diagram As shown in above diagram, cell grouping is carried out using anti A, anti B and anti AB commercially available sera. Serum grouping is carried out using A cells, B cells and O cells.