CLS 443 Blood Bank - Lecture 1: Review Genetics Immunology Reagents

Blood group system

Groups of antigens on the RBC membrane that share related serologic properties and genetic patterns of inheritance

Chromosomes

Structures within the nucleus that contain DNA

Mitosis

Cell division of somatic cells—results in the same # of chromosomes

Meiosis

Cell division in gametes that results in half the # of chromosomes

Phenotype

Observable expression of inherited traits

Genotype

Actual genetic makeup; determined by family studies or DNA testing

Pedigree chart

Diagrammatic method of illustrating the inheritance patterns of traits in a family

Gene

Basic unit of inheritance on a chromosome

Genetic loci

Site of a gene on a chromosome

Alleles

Alternate forms of a gene at a given locus

Antithetical

Opposite allele

Polymorphic

Genetic system that expresses 2 or more phenotypes (i.e., Rh system, pg 153-154)

Amorphic

A gene that does not express a detectable product

Hemizygous

One chromosome has a copy of the gene while the other chromosome’s gene is deleted or absent

Dosage effect

Stronger agglutination when a RBC Ag is expressed from homozygous genes

Cis

2 or more genes on the same chromosome of a homologous pair

Trans

Genes inherited on opposite chromosomes of a homologous pair

Linked

When 2 genes are inherited together by being very close on a chromosome

Haplotype

Linked set of genes inherited together because of close proximity on a chromosome

Crossing over

Exchange of genetic material during meiosis between paired chromosomes

Suppressor genes

Genes that suppress the expression of another gene

Mutation

Change in a gene that is permanent and heritable; can be caused by radiation, chemical damage, viruses, etc.

Autosomal dominant

Trait appears whenever the allele is present, i.e., either in the homozygous or heterozygous genotype (RR or Rr); found in each generation of family; equal frequency in males and females

Autosomal recessive

Must be homozygous genotype (rr), to express trait; equal frequency in males and females; both parents must be heterozygous to express trait

Codominant

In the heterozygous genotype, both alleles are equally expressed; most common pattern found in human blood groups

Sex linked dominant

Male carriers trait on X chromosome. He will give trait to NONE of his sons. All of his daughters will have trait. These females’ offspring (male or female) will have a 50/50 chance of inheriting the trait and is expressed

Sex linked recessive

Father will always express trait, but never pass it on to sons. All daughters will be carriers. Half of her sons will express trait. Half of her daughters will get trait, but only if rare match to another carrier resulting in homozygous female with the trait will be expressed

• h

• Bombay

Amorph/reg gene of blood group H, and its homozygous phenotype

• R_null/x^or

• Rh null

Amorph/reg gene of blood group Rh, and its homozygous phenotype

• K^o

• Kell null

Amorph/reg gene of blood group Kell, and its homozygous phenotype

• Lu/In(Lu)

• Lu(a-b-)

Amorph/reg gene of blood group Lutheran, and its homozygous phenotype

• Jk

• Jk(a-b-)

Amorph/reg gene of blood group Kidd, and its homozygous phenotype

• Fy

• Fy(a-b-)

Amorph/reg gene of blood group Duffy, and its homozygous phenotype

1. Prenatal diagnosis

2. Carrier testing

3. Pre-symptomatic testing

4. Relationship testing (human identitty)

Types of genetic testing (4)

• Paternal testing

• Forensic cases

• Historical investigations

• Missing persons investigation

• Mass disasters

• Military DNA “dog tag”

• Convicted felon DNA databases

Relationship testing (7)

Direct exclusion

(Relationship testing) exclusion of paternity when a child has a trait that neither parent demonstrates

Indirect exclusion

(Relationship testing) failure to fund an expected marker in a child when the alleged father is apparently homozygous for the gene

Obligatory gene

(Relationship testing) gene that should be inherited from the father to prove paternity

Paternity index

(Relationship testing) chance that the alleged father is the biological father compared to the chance that an untested male (random man) is the father

Direct exclusion

(Relationship testing interpretation) child has a trait present that neither parent posses

Indirect exclusion

(Relationship testing interpretation) child lacks a gene that should be inherited from the parent in question

Inclusion

(Relationship testing interpretation) When the child has the predictable traits that are expected from the parent in question

• ABO

• Rh

• MNSs

• Kell

• Duffy

• Kid

RBC antigens commonly used in parentage testing (6)

• PGM1

• ACP

• ESD

• Hp

• Gc

RBC enzymes and serum proteins commonly used in parentage testing (5)

• Gm

• Km

• Am

Immunoglobin allotypes commonly used in parentage testing (3)

A and B locus

HLA commonly used in parentage testing

Mendel’s First Law of Inheritance

Law of independence or random segregation, in terms of dominant (designated by uppercase letters) and recessive (designated by lowercase letters)

Mendel’s Second Law of Inheritance

The law of independent assortment and that genes for different traits are inherited separately from each other. This allows for all possible combinations of genes to occur in the offspring

p² + 2pq + q² = 1

(p = gene frequency; p² = frequency of genotype)

Hardy-Weinberg law formula

Type II

Blood bank immune responses commonly fall within the (——) hypersensitivity category

Hemolysis (complement) or extravascular sequestration

If a patient develops an Ab to transfused Ag, the patient’s Abs can cause subsequent transfusion reactions by attacking transfused cells and destroying them, either through (——) or (——)

• Pentamer

• Does not pass the placenta

• Readily binds C’

• RT or lower

• First phase (IS)

IgM characteristics (structure, placenta, complement, rxn temp, Ab detection testing)

• Monomer (80% of Igs in sera)

• Passes through placenta

• IgG₃ > IgG₁ > IgG₂ > IgG₄

• 37°C

• AHG test phase

IgG characteristics (structure, placenta, complement, rxn temp, Ab detection testing)

Primary response

One of the phases in the humoral response; lag time approximately 5-7 days or greater, where IgM antibody is produced first, followed by IgG Ab production

Secondary/Amnestic Response

One of the phases in the humoral response; lag time approximately 1-2 days, where IgG Ab is produced; usually no IgM Ab is produced since this exposre was NOT the first time the body recognized the Ag

Kidd (Jka)

Ab notorious in blood bank for causing an amnestic response because the titer is often too low to for testing to detect

1. Sensitization (i.e., Ab uptake)

2. Lattice formation (i.e., agglutination)

Describe the 2 stages involved in a hemagglutination reaction

Hemolysis

Dependent on the activation of binding complement and completion of activation pathway; considered a “positive” reaction

• Serum:Cell Ratio (SC ratio)

• Temperature

• Time

• pH

• Ionic strength

• Affinity/Ab uptake

• Immunoglobulin class

Certain factors that can influence the sensitization phase of hemagglutination (7)

• Distance between RBCs

• Zeta potential

• Optimal concentrations of Ab and Ag (prozone, postzone, equivalence)

• Effect of centrifugation

• Size of immunoglobulin (IgM vs igG)

• # of binding sites on RBC

Certain factors that can influence the lattice formation phase of hemagglutination (6)

Liver

Complement proteins are produced in the…

• Lysis

• Opsonization

• Activation of inflammatory response

• Clearance of immune complexes

Complement eliminates foreign substances through… (4)

• Polyspecific

• Monospecific

(—2—) AHG reagents are used in blood bank to detect C3b in the complement system

Classic pathway

Complement pathway that is Ab dependent (IgM or IgG) where C1 interacts with Ag-IgM complex or aggregated Ag-IgG complex

• Mannose binding lectin (MBL)

• Mannose, fucose, N-acetylglucosamine

In the lectin pathway, activation is Ab dependent where (——), a serum protein, binds to (—3—) on bacterial cell walls, yeast cell walls, or viruses. This pathway otherwise resembles the classical pathway structurally and functionally

• Components of microbial cell surfaces

• Immunoglobulin

• Properdin, Factor H, decay accelerating factor CD55

The alternative pathway activation occurs when (——) (e.g., ueast walls, bacterial cell wall lipopolysaccharide [endotoxin]) or (——) (e.g., nephritic factor, aggregated IgA) cleave small amounts of C3; this pathway is regulated by (—3—)

Test tube

(Hemagglutination method) technique (shaking of tube) must be acquired and is critical, saline washing and CCs are needed as part of testing procedure, more subjective endpoint

Gel Card

(Hemagglutination method) technique requires specialized equipment and gel tube, saline washing and CCs

Solid phase

(Hemagglutination method) technique requires specialized equipment and microtiter plate, saline washing and use of IgG coated indicator RBCs, less subjective endpoint

Positive

In hemagglutination testing, if the supernatant has a reddish color, hemolysis is indicated and it is interpreted as a (——) reaction

False positive

Increased proteins can cause RBCs to clump and stack (rouleaux), which is a (——) reaction; described as a “stack of coins”

Presence of two different cell populations (type A and O) aka chimerism

What causes mixed field (mf) agglutination

• Anti-A = blue

• Anti-B = yellow

• Anti-A,B = clear

Color of reagent antisera (3)

Potentiator/Enhancement media

Reagent media of various properties to enhance antibody uptake and/or agglutination

• Polyspecific reagent - IgG and C’ Abs (clear)

• Monospecific reagent - IgG Ab only (green)

• Monospecific reagent - C3b/C3d only (clear)

What do the different antiglobulin reagents detect, and what color are they? (3)

Dolichos biflorus

A1 lectin

Polyclonal antisera

Antisera with several different clones of B cells that secrete Ab

Monoclonal antisera

Antisera with single clones of B cells that secrete one Ab

Hybridoma

Hybrid cell formed by the fusion of a myeloma cell and a Ab producing cell, used in the production of monoclonal Abs