ImmunohematologyBlood Banking (Group 1)

Blood Group Antigen & Antibody

Blood Group Antigen Antibody Ig

A A B

Predominantly IgM & small quantities of

IgG

B B A

AB A, B NEITHER

O NEITHER A, B

ABO Antibodies

• Individuals normally produce Ab directed against the A &/or B Ag(s) absent from their RBCs.-NATURALLY OCCURING, because they are produce without any exposure to RBCs.

• Produce strong direct agglutination reactions during ABO testing

ABO Antibodies

• Are initiated at birth, but titre are too low until 3-6 months– Test before these months are considered invalid

because of maternal origin of Ig

• 5-10 years, Ab production peaks then declines later in life

• Elderly people usually have lower levels of Anti-A & Anti-B; therefore Ab may be undetectable in the reverse grouping.

ABH Antigens

• Results from the interaction of genes at three separate loci (ABO, Hh & Se).

– Produce specific glycosyltransferases that add sugars to a basic precursor substance.

– A, B, & H Ag are formed from the same basic precursor material paragloboside or glycan

ABH Antigens

• on the RBC are constructed on oligosaccharide chains of a type 2 precursor substance

• Developed early in fatal life but do not increase much in gestational period.

• 2-4 years of age• Phenotypic expression may vary in race, genetic

interaction and disease states– Expression of A & B Ag on the RBCs is fully

developed and remains constant throughout life

ABH Antigens

• H- Antigen– Precursor structure on which A & B Ag are

made. – H gene must be inherited to form ABO Ag on

the RBCs whereas Se for Ag in secretions.

Blood group Complement (C)

• Is a complex group of over 20 circulating and cell membrane proteins that have a multitude of functions within the immune response.

• Primary roles include direct lysis and assisting of opsonization and production of peptide fragment split products which play roles in inflammatory responses.

• can also have detrimental effects for the host; it contributes to inflammation and tissue damage and it can trigger anaphylaxis

• Complement components circulate in inactive form as proenzyme

Blood group Complement

• Complement proteins are activated in a cascade of events through three main pathways:– Classical– Alternative– Lectin– Then eventually goes to MAC (Membrane

Attack Complex)

Blood group Complement

Blood group Complement