Why Is the Rh D Antigen Important in Blood Transfusions?

Why Is the Rh D Antigen Important in Blood Transfusions?

Anemia Treatment Options For Medical Students

Write a short note on the blood group.
Answer:

Blood groups are genetically determined antigens that can be detected on the RBC surface by specific antibodies.

Name of the Blood Group with Antigens

“What is the Rh D antigen and why is it important?”

ABO Blood Group

• The ABO system is the product of one gene locus situated on chromosome 9, which determines the expression of ABO blood groups on RBCs, endothelial cells, and some epithelial cells.
• The basic precursor substance in antigens has a short chain of sugars.
• There are two types of chains;  Type 1 and Type 2 chains, which differ from each other in the way the terminal galactose joins the N-acetylglucosamine residue.
• The basic precursor substance is converted to an H substance by L-fucosyltransferase
• A gene codes for a transferase that attaches N-acetylgalactosamine to the precursor substance, thereby producing A antigen (blood group A).

Importance of Rh factor in blood transfusion

“Understanding the Rh D antigen in blood transfusions”

• B gene codes for a transferase that attaches galactose to the precursor substance to produce B antigen (blood group B).
• O gene is inactive; hence, neither A nor B antigens are present on the surface of blood group O RBCs.
• Group AB individuals have H antigen that carries both A or B active sugars.
• An individual receives one blood group antigen from the mother and one from the father.
• Antibodies belonging to the ABO system are naturally occurring, IgM-type, complete antibodies.
• The A group contains about twenty subgroups, of which Al and A2 are the most common. A1 makes up 80% of all A-type blood,d while A2 makes up for the rest.

“Case studies on outcomes of Rh D antigen management”

Bombay Blood Group (hh)

Some individuals do not inherit the H gene and are not able to express substance H on their RBCs, and thus, do not produce A or B antigens. Instead, they produce antibodies to substance H and both A and B antigens. They can receive blood only from other donors but can donate like group O individuals.

“Importance of Rh D antigen matching in transfusions”

Blood Group Rh Antigen System

• Rh antigen system has three closely linked gene loci, coding for D antigen (there is no d antigen), C and/or c antigen, and E and/or e antigen. Thus, the antigens produced are C, D, E, c, and e.
• An individual may have similar or different sets of these three Rh antigens on each chromosome; for example, CDE/cde, cde/cde, or CdE/cdE (each person inherits one trio
  gene from each parent).
• Individuals who are positive for D antigen are considered Rh-positive (85% of the population), and those who lack it are Rh-negative.
• Individuals with a weak variant of D antigen, called the Du variant, are also considered Rh-positive.
• Alloimmunization, i.e., the formation of an antibody against an antigen,n occurs if a person is exposed to an Rh antigen that is not on the patient’s RBCs.
• The majority of clinically important antibodies that produce a transfusion reaction are warm-reacting (IgG) antibodies (For Example. anti-D, anti-Kell) rather than cold-reacting (IgM) antibodies.

Rh incompatibility in transfusion

“Asymptomatic vs symptomatic stages of Rh D reactions”

Blood Group Duffy Antigen System

African–Americans commonly lack Duff (Fy) antigens on their RBCs, which protects their cells from Plasmodium vivax infestation, since P. vivex requires Duff antigen as a receptor to bind to the RBCs.

Blood Group Lewis Antigens

They are closely related to ABH antigens and are produced in body secretions. Naturally occurring IgM antibodies develop against these antigens, but they are generally weak antibodies of no clinical importance.