Week 1: ABO Blood Group System

if a patient has no historical blood type testing, what should be done?

1. draw 2nd specimen and also test ABO type

2. another technologist tests

1+ agglutination

a lot of free floating cels with small sized agglutinates

2+ agglutination

clear background with medium sized agglutinates

3+ agglutination

clear background with two or three giant agglutinates

4+ agglutination

solid button or agglutinate

mixed field reaction (MF+)

hazy background with solid or giant agglutinates

grading agglutination in gel testing

agglutinates are observed from bottom of gel column to top

what type of testing is this?

agglutination in gel testing

ABO testing: forward type

1. reagent = antisera

2. patient RBCs

3. determines the patient’s antigens

ABO testing: reverse type

1. reagent = RBC

2. patient’s plasma/serum

3. determines the patient’s antibodies

when do ABO antibodies begin to develop?

4 months old

ABO antibodies are usually what type of immunoglobulin?

IgM

anti-A,B

1. made by some O types

2. dual specificity

3. IgG

how old until ABO antigens are fully developed?

2-4 years

where are ABO genes located?

chromosome 9

the O allele is _________

amorph

where is the gene for the H antigen located?

chromosome 19

H antigen

1. precursor to A and B

2. last sugar added to the oligosaccharides

what does H gene (HH or Hh) encode?

1. L-fucosyltransferase

2. adds L-fucose to type 2 precursor substance on RBC

which blood type has the highest amount of H antigen present?

O

the hh genotype is known as what?

bombay phenotype

what blood type does the bombay phenotype mimic during testing?

O

bombay phenotypes will develop _________ whereas typical O types have the H antigen

anti-H

anti-H is what type of immunoglobulin?

IgM

Ulex europaeus

1. lectin

2. has anti-H specificity

bombay + anti-H → ?

negative reaction

O + anti-H →

positive reaction

what does the A gene encode?

1. N-acetylgalactosaminyltransferase

2. adds N-acetyl-Dgalactosamine molecule to H antigen

how do the subclasses A1 and A2 differ?

1. A1 gene produces N-acetylgalactosaminyltransferase to be made in high amounts

2. A1 people convert antigen site 4x more than A2 people

anti-A1

1. some A2 people will develop an antibody against A1

2. 1-8% of A2 and 22-35% of A2B

other less common A subgroups

1. A3

2. Am

3. Ax

4. Ael

A3 can have a __________ reaction with anti-A if human source antisera is
used

mixed-field

______ usually agglutinates with anti-A,B weakly and no reaction with anti-A

Ax

lectin Dolichos biflorus

1. only binds A1 antigen

2. other A subgroups will not agglutinate

what does the B gene encode?

1. D-galactosyltransferase

2. adds D-galactose to H antigen

which blood type has the least amount of H antigen?

AB

adding A and B antigens to the RBC membrane decreases the amount of ___________ present

H antigen

which blood types can potential develop anti-H has a result of low levels of H antigen?

A1 and A1B

order of blood types with highest to lowest amounts of H antigen

O > A2 > B > A2B > A1 > A1B

secretor gene is found where?

chromosome 19

secretor gene function

1. creates ABH soluble substances in body fluids

2. 80% of people are secretors

what does the secretor gene encode?

1. L-fucosyltransferase

2. adds L-fucose to type-1-precursor substance

where is type-1-precursor substance found?

secretory tissues

the secretion of ABH does NOT affect what?

ABH antigen development on RBC membrane