Question

someone has type A+ blood. Sketch how that would look on a blood typing chart. What type of antigens and antibodies would they have? what would their alleles be?

Answer 1

ABO blood group

• As the name ABO blood group consists of three letters, ABO blood typing designates the presence or absence of just two antigens, A and B. Both are glycoproteins.
• People whose erythrocytes (Red blood cells) have A antigens on their erythrocyte membrane surfaces are designated blood type A, and those whose erythrocytes have B antigens are blood type B.
• People can also have both A and B antigens on their erythrocytes, in which case they are blood type AB.
• People with neither A nor B antigens are designated blood type O. ABO blood types are genetically determined.

Blood type Antibodies

• Normally the body must be exposed to a foreign antigen before an antibody can be produced. This is not the case for the ABO blood group.
• Individuals with type A blood—without any prior exposure to incompatible blood—have pre-formed antibodies to the B antigen circulating in their blood plasma. These antibodies, referred to as anti-B antibodies, will cause agglutination and hemolysis if they ever encounter erythrocytes with B antigens.
• Similarly, an individual with type B blood has pre-formed anti-A antibodies.
• Individuals with type AB blood, which has both antigens, do not have pre-formed antibodies to either of these.
• People with type O blood lack antigens A and B on their erythrocytes, but both anti-A and anti-B antibodies circulate in their blood plasma.

Rh Blood Groups

• The Rh blood group is classified according to the presence or absence of a second erythrocyte antigen identified as Rh.
• Although dozens of Rh antigens have been identified, only one, designated D, is clinically important. Rh group is distinct from the ABO group, so any individual, no matter their ABO blood type, may have or lack this Rh antigen.
• Those who have the Rh D antigen present on their erythrocytes are described as Rh positive (Rh+) and those who lack it are Rh negative (Rh−).
• When identifying a patient’s blood type, the Rh group is designated by adding the word positive or negative to the ABO type. For example, A positive (A+) means ABO group A blood with the Rh antigen present, and AB negative (AB−) means ABO group AB blood without the Rh antigen.

Determining ABO Blood Types

• A patient’s blood type quickly determined using commercially prepared antibodies. An unknown blood sample is allocated into separate wells. Into one well a small amount of anti-A antibody is added, and to another a small amount of anti-B antibody. The blood is also tested for Rh antibodies by adding anti D in another well.

• If the antigen is present, the antibodies will cause visible agglutination of the cells.
• For A + blood sample, we can see agglutination in well containing Anti A antibodies, and also in well containing Anti D antibodies.
• This indicates that A + blood contains A and D (Rh) antigens.
• It also contains Anti B antibodies and Anti D antibodies.

• For other blood types, a typical blood typing looks as given in the below table

Genetic Inheritance Patterns

• ABO blood types are inherited. They are determined by genes on chromosome 9, and they do not change as a result of environmental influences during life.
• An individual's ABO type results from the inheritance of 1 of 3 alleles (A, B, or O) from each parent.
• An individual with A+ blood type will have alleles A and O.
• Both A and B alleles are dominant over O. As a result, individuals who have an AO genotype will have an A phenotype, that is blood type A.
• For other blood types, the possible outcomes are shown below:

  Parent Alleles	A	B	O
  A	AA (A)	AB (AB)	AO (A)
  B	AB (AB)	BB (B)	BO (B)
  O	AO (A)	BO (B)	OO (O)

The possible ABO alleles for one
parent are in the top row and the
alleles of the other are in the left
column. Offspring genotypes
are shown in black. Phenotypes
are red