Blood group and ABO antigens Lecturer Bahiya Osrah

History: Karl Landsteiner Discovered the ABO Blood Group System in 1901 Blood types: Type A, Type B, Type AB, & Type O The identification of blood group depends on the antigen and antibodies produced by the immune system. http://www.nobelpreis.org/castellano/medizin/images/landsteiner.jpg

Introduction Antigens: chemical structures imparting specific properties to the surface of the RBC Antibodies: protein substance developed in response to foreign body substances Three antigens we need to focus on: A, B, and H antigens that are usually expressed on the red blood cells surface. The presence or absence of the A, B, and H antigens is controlled by the H and ABO genes

ABO Basics Blood group antigens are actually sugars attached to the red blood cell. Antigens are “built” onto the red cell. Individuals inherit a gene which codes for specific sugar(s) to be added to the red cell. The type of sugar added determines the blood group.

H Antigen The H gene codes for an enzyme that adds the sugar fucose to the terminal sugar of a precursor substance (PS) The precursor substance (proteins and lipids) is formed on an oligosaccharide chain (the basic structure)

RBC Precursor Structure Glucose Galactose Precursor Substance (stays the same) N-acetylglucosamine Galactose

Formation of the H antigen RBC Glucose H antigen Galactose H enzyme is fucosyltransferase N-acetylglucosamine Galactose Fucose

A and B Antigen The “A” gene codes for an enzyme (transferase) that adds N-acetylgalactosamine to the terminal sugar of the H antigen N-acetylgalactosaminyltransferase The “B” gene codes for an enzyme that adds D- galactose to the terminal sugar of the H antigen D-galactosyltransferase

Formation of the A antigen RBC Glucose Galactose N-acetylglucosamine Galactose N-acetylgalactosamine Fucose

Formation of the B antigen RBC Glucose Galactose N-acetylglucosamine Galactose Galactose Fucose

Genetics The H antigen is found on the RBC when you have the Hh or HH genotype, but NOT from the hh genotype The A antigen is found on the RBC when you have the Hh, HH, and A/A, A/O, or A/B genotypes The B antigen is found on the RBC when you have the Hh, HH, and B/B, B/O, or A/B genotypes

ABO Type Frequencies In U.S. Per Cent O 45% A 40% B 11% AB 4%

Landsteiner’s Rule Individual’s will form immune antibodies to ABO blood group antigens they do not possess. Critical for understanding compatibility between ABO blood groups.

Antibody clinical significance Immunizations are frequently done to protect us from disease. Receive Hepatitis B immunization. Actual bits of hepatitis virus injected. Body recognizes as foreign and produces an immune antibody. Subsequent exposure to real Hepatitis B virus will result in destruction of the virus by immune antibodies. ABO antibodies are immune and will result in destroying incompatible cells which may result in the death of the recipient.

Genetics Two genes inherited, one from each parent. Individual who is A or B may be homozygous or heterozygous for the antigen. Heterozygous: AO or BO Homozygous: AA or BB Phenotype is the actual expression of the genotype, ie, group A Genotype are the actual inherited genes which can only be determined by family studies, ie, AO.

Group O Has NO antigens on RBC surface Approximately 45% of the population is group O. Has NO antigens on RBC surface Has anti-A & anti-B antibodies in the plasma Universal Donor: can be given to any blood type  no antigens on the RBCs Genotype OO = Phenotype O

Group A Approximately 40% of the population is group A. No B antigens present. Has A antigens on the RBC surface Has anti-B antibodies in the plasma Genotypes AA & AO = Phenotype A

Group B Approximately 11% of the population is group B. No A antigens present. Has B antigens on the RBC surface Has anti-A antibodies in the plasma Genotype BB & BO = Phenotype B

Group AB Approximately 4% of the population is group AB. Has A & B antigens on the RBC surface Has NO antibodies in the plasma Universal Recipient: can receive Type A, Type B, Type AB, or Type O blood  NO antibodies in plasma to react with antigens Genotypes: AB = Phenotype AB NOTE: This slide is in error as it only illustrates presence of one antigen not 2.

Hemolysis If an individual is transfused with an incompatible blood group destruction of the red blood cells will occur. This may result in the death of the recipient.

Summary A Anti-B A or O B Anti-A B or O AB A and B none AB, A, B or O Blood Group Antigens on cell Antibodies in plasma Transfuse with group A Anti-B A or O B Anti-A B or O AB A and B none AB, A, B or O O None Anti-A & B

Rh (D) Antigen Rh refers to the presence or absence of the D antigen on the red blood cell. Discovered by Landsteiner & Wiener in 1937 Discovered in the Rhesus monkey Rh is an antigen on the RBC surface Rh + has the antigens on the RBC (85% of population) Rh – does NOT have the Rh antigens Rh + can accept Rh + or Rh – blood Rh – can accept ONLY Rh - blood

Rh (D) Antigen Production of antibody to D requires exposure to the antigen. The D antigen is very immunogenic, ie, individuals exposed to it will very likely make an antibody to it. For this reason all individuals are typed for D, if negative must receive Rh (D) negative blood. Because the Rh(D) positive individuals already have D antigen and that will trigger the immune response of the negative individuals to the D-antigens and that will cause death

Erythroblastosis fetalis Rh– mother and Rh+ father  Rh+ child 1st pregnancy during pregnancy fetal Rh pos rbc’s escape into maternal circulation (antigents) Mother develops antibodies to baby’s Rh+ antigens 2nd pregnancy with Rh+ child  mother’s anti-Rh antibodies attack unborn child’s RBCs Prevention: shot of Rhogam shortly after birth of first Rh+ baby to block development of antibodies Antigen-antibody reaction due to mixing of Rh+ blood of fetus with Rh- blood of mother during 2nd Rh+ pregnancy

Blood Typing There are 2 components to blood typing: Test unknown cells with known antibodies Test unknown serum/plasma with known rbc’s The patterns are compared and the blood group is determined.

Slide Blood Typing - continued The slide is divided into halves. On one side a drop of anti-A is added, this will attach to and cause clumping of rbcs possessing the A antigen. On the other side a drop of anti-B is added which will cause clumping of rbcs with the B antigen. A drop of rbcs is added to each side and mixed well with the reagent. The slide is tilted back and forth for one minute and observed for agglutination (clumping) of the rbcs

Interpretation of Slide Typing Testing with Anti-A Anti-Serum If an rbc contains the A antigen the red blood cells will be agglutinated by anti-A, a positive reaction. If an rbc does not have the A antigen there will be no clumping, a negative reaction.

Interpretation of Slide Typing Testing with Anti-B Anti-Serum If an rbc contains the B antigen the red blood cells will be agglutinated by anti-B, a positive reaction. If an rbc does not have the B antigen there will be no clumping by anti-B, a negative reaction.

Slide Blood Typing Group A An unknown rbc suspension is added to known anti-sera. The left hand of the slide contains anti-A which reacts with the unknown cell. The right hand side contains anti-B which does not react with the cell.

Slide Blood Typing Group B An unknown rbc suspension is added to known anti-sera. The left hand of the slide contains anti-A does not react with the unknown cell. The right hand side contains anti-B which reacts with the cell.

Slide Blood Typing Group O The left hand of the slide contains anti-A does not react with the unknown cell. The right hand side contains anti-B does not react with the unknown cell.

Slide Blood Typing Group AB The left hand of the slide contains anti-A which reacts with the unknown cell. The right hand side contains anti-B which reacts with the unknown cell.

Summary of Slide Typing Anti-A Anti-B Blood Group NEG O POS A B AB

Any questions??

References Cte.unt.edu/health/curriculum/blood_types.ppt Cls.umc.edu/COURSE/CLS325/Week2/ABOsystem.ppt www.austincc.edu/mlt/clin1/ABO.ppt