The ABO blood
group system was first identified by Karl Landsteiner in 1901 (healthable.org) and is up to date the most important
of the 35 known human blood type classifications, which also include the Rhesus
system (not investigated in this work). The ABO typing is based on the presence
of one, both, or neither of the A and B antigens on erythrocytes (the red blood cells, or RBCs) (wikipedia.org). These antigens are
carbohydrates attached to specific cell-surface molecules on RBCs (Campbell et al. 2017, p. 330). RBCs with antigen
A on their surface are said to belong to blood group A; RBCs with antigen B belong
to blood group B; RBCs with both antigens belong to blood group AB; RBCs with
no antigens belong to group O (Fig. 1) (healthable.org). The
latter type was discovered by Alfred von Decastello and Adriano
Sturli in 1902 (wikipedia.org).
Plasma of the blood types A and B contains
antibodies that bind to antigens of the opposite type, whereas type AB contains
no antibodies and type O contains both (Fig. 1). Blood transfusions require careful blood typing and compatibility
because foreign antigens can trigger an immune response – antibodies in the
plasma will attack the transfused blood cells that contain the corresponding
antigens, also called isoagglutinins (redcap.com.my). This is known as the
antibody-antigen reaction, or agglutination – blood particles will clump up
which is a dangerous condition (healthable.org).
The ABO blood groups depend on the inherited genotype.
Each person’s blood group gene has two alleles of the possible three: IA, IB and i. The
specific combinations of two alleles determine the phenotype of the blood (Fig.
2) (Campbell et. Al 2017, p. 330). As seen in the Fig. 2, only four phenotypes
result from the six possible genotypes. Reactions resulting from adding RBCs from
the four groups to the corresponding serum are also shown in Fig. 2.
The aim of
this experiment was to learn about the different blood types, understand the
differences between them, demonstrate how to type blood using a blood sample
with known blood type, and identify four unknown types of blood from donors as
well as one’s own blood type based on whether the agglutination reaction was
present or not (Nordeide et al. 2017).