The term blood banking refers to the collection, processing,
preservation, preparation and distribution of blood and blood components and
derivatives. The establishment where
this procedure takes place is called a blood bank.
A related term which has been used synonymously nowadays with
blood banking is immunohematology which is the study of blood–related
antigens and antibodies as applied to situations such as blood transfusion and
hemolytic disease of the newborn.
Scope of function of a modern blood bank:
1. Recruiting blood donors.
2. Collecting and storing whole blood or
components from volunteer or autologous donor.
3. Typing, screening and preparing patient and
donor for blood transfusion.
4. Detecting and identifying antibodies in
potential blood recipients or pregnant women.
5. Establishing a database to support suspected
or potential disorder.
6. Processing and dispersing blood components.
7. Performing paternity testing.
8. Conducting tissue typing prior to organ
transplantation and participating in the processing of human materials (e.g.
bone banking)
Related terminologies
1. Blood groups – refers not only to groups of
erythrocyte antigens but also to other blood components, including leukocytes,
platelets and plasma.
2. Factor – used to include classic antigens as
well as those recognized by immunologic methods not utilizing a specific
antibody.
3. Hemotherapy – refers to the selection with
preparation and infusion of appropriate blood, blood components or derivatives
for each individual patient.
4. Specificity – refers to the appearance of a
substance that can only recognized by immunologic techniques and is commonly
used in reference to leukocyte antigens; it may also indicate a complex antigen
or a fraction of an antigen.
Objectives of a blood bank
technologist
1. Prevention of antigen–antibody interaction in
the body. This is accomplished by identifying those patients who have an
antibody supplying blood which lacks the corresponding antigen.
2. To prevent antibody production
Blood bank tests:
1. Blood grouping – is the process of testing
cells to determine which antigens are present and which are absent
2. Antiglobulin test – to aid in weak
agglutination
3. Compatibility testing – to ensure safe blood
transfusion
4. Determination of unexpected antibodies.
a. Antibody screening tests – are used to detect
those people whose sera contain one or more unexpected antibodies
b. Antibody identification tests – defines the
specificity of the antibody
************ BLOOD GROUP GENETICS ************
Genetics is the study of the
basic concepts of inheritance and heredity. This is the basic foundation of
blood banking as it determines how blood group is being passed to the newborn,
thus preventing transfusion reaction.
Definition of terms:
1. Alleles, allelic genes, allelomorphs –
alternate form of genes to occupy the same locus.
2. Allelic – when two alternate forms of genes
have the capacity to occupy the same locus.
3. Locus – the specific position occupied by a
gene on the DNA chain.
4. Chromosomes – long, thread – like structures found
in the nucleus of a cell. They are made up of DNA on a protein framework.
5. Homozygous – when allelic genes are
identical.
6. Heterozygous – when allelic genes are
indifferent
7. Genes – segments of the chromosomes. They are
responsible for all bodily characteristics. They are the basic units of
heredity.
8. Dominant gene – a gene which is always
expressed, whether it is in homozygous or heterozygous state.
9. Recessive gene – a gene which is expressed
when it is in the homozygous state.
10. Genotype – refers to the sum of all genes
inherited from both parents whether they are expressed or not.
11. Phenotype – refers only to a detectable
products of a gene, demonstrated to direct testing.
12. Codon – a series of triplets making a gene.
13. Penetrance – refers to the degree of
expression of a given gene in different individuals. It represents a graded
response varying from person to person.
14. Expressitivity – describes the degree of
expression of a given gene in different individuals. It represents a graded
response to varying from person to person.
15. Structural gene – genes which direct the
construction of proteins.
Basic facts about genetics
1. Human have 22 pairs of autosomes and a pair
of sex chromosomes, XX in females and XY in males.
2. Chromosomes are made up DNA which carries the
genetic message.
3. During the reduction division stage of
meiosis, homologous chromosomes exchange segments of genetic material so that
each chromosome entering the gamete contains variable amount of maternal and
paternal genetic material. This process of exchanging segments of chromosomes
is called crossing over.
4. A new organism is formed when an ovum and a
sperm, each carrying one–half of the genetic material, unites to form a
zygote.
5. The building blocks of DNA are called
nucleotides, each of which is composed of a phosphate group, deoxyribose and a
nitrogenous base. The phosphate group and deoxyribose group are the same in all
nucleotides but there are four different nitrogenous bases – 2 purine bases
(adenine and guanine) and 2 pyrimidine (cytosine and thymine). The genetic
message is determined by the sequence in which these nucleotides are joined.
6. DNA serves as a template to produce messenger
ribonucleic acid and the genetic message is transcribed to the mRNA. The
message is made up of 3 letter words called codons, the letters being the
nucleotides. Each codon designates one amino acid.
7. Messenger RNA moves into the cytoplasm and is
read by the ribosomes.
8. Amino acids which are joined by peptide bonds
are called polypeptides. Polypeptides are the basis for all proteins.
Genes determines blood group
antigens
It is probable that those blood
group antigens which are proteins are direct product of gene action. The
polypeptide may be inserted into the membrane as a single chain or it may be
folded, perhaps joined to other chains and inserted as a complex structure. On
the other hand, because genes control the production of proteins only, the
construction of oligosaccharide antigens must involve intermediate step. The
intermediate step in the production of enzymes (which are proteins) called
transferases which assemble individual sugars into chains and more complex
molecules. Transferases catalyze the transfer of a particular sugar molecule
from the source to a specific receptor molecule (substrate). As each transferase
adds its sugar, a new structure is formed and this structure may then be the
substrate used by another transferase.
Two types of gene interaction:
1. Epistatic – when the interaction is between
genes at different loci.
2. Allelic – when it involves alleles at the
same locus.
Mode of inheritance
A. Autosomal Dominant or Codominant
Inheritance
An autosomal
dominant or codominant trait shows a very characteristic pattern that is easy
to recognize. The trait never skips a generation and a mating of 2 heterozygots
has a probability of producing a child positive for a trait three times out of
4.
Example: Blood group antigens
B. Autosomal recessive Inheritance
Any of the
following is suggestive of an autosomal inheritance
1. A great majority of affected (double
recessive) parents being affected.
2. Usually, normal offspring from a mating of a
normal parent with an affected parent, especially if the recessive trait is
rare.
3. Consanguinity (common ancestry in paternal
line) of the person showing the trait.
Example: Bombay phenotype
C. Sex linked Dominant or Codominant
Inheritance
Sex linked
dominant or codominant pedigrees show affected males with normal wives
transmitting the trait to daughters only.
Example: Xga Blood group
D. Sex–linked Recessive Inheritance
A much
larger number of affected males than females is the first thing to look for.
Affected males do not come from affected fathers but from carrier mothers, who
may often be recognized affected brothers, fathers or uncles.
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