TOPIC 1 INTRODUCTION TO IMMUNOHEMATOLOG

1. TOPIC 1
INTRODUCTION TO IMMUNOHEMATOLOGY

2. LEARNING OUTCOME:
• At the end of this lecture, students should be able to:
Discuss the patterns of inheritance of A and B genes
Describe the synthesis of H, A and B antigens
Name the specific transferase for the A, B and H antigens
State the phenotype of individuals with the Bombay phenotype
State the characteristics genotype of secretor and non secretor
Identify the product or products found in the saliva of persons of
various ABO grouping

3. INTRODUCTION
• Immunohematology is a special branches of medical sciences that deals
with the general procedures involving in collecting, preparing, storing
and transfusing blood
• Commonly known as Blood Banking
• Def: Refers to the immunologic reactions involving blood components
• It is an application of the principles of immunology to the study of
• red cell antigens and
• their corresponding antibodies on blood for resolving the problems of blood
transfusion

4. INTRODUCTION
• Unit of donated whole blood can be separated into
variety of blood components and derivatives which
allows it to be used for a number of therapeutic
purposes. Examples of blood components and
derivatives include:
• Fresh frozen plasma (FFP)
• Cryoprecipitate
• Platelets
• Factor VIII concentrate

5. Functions of a blood bank
i. Recruitment and retention of voluntary and replacement blood donors
ii. Selection of donors (i.e. to determine the suitability)
iii. Blood collection
iv. Screening of blood for various blood borne diseases
v. Blood component preparation
vi. Storage of blood and blood products
vii. Record keeping of all the above
viii. Laboratory procedures (e.g. serologic testing)
ix. Participation in the clinical use of blood and blood components
x. Teaching and training of personnel (medical staff)
xi. Research and development

6. BLOOD GROUP GENETICS
Concerned with the way in which the different blood groups are inherited,
from parents to child

7. Chromosomes and Genes
 In the human body, the nucleus of each body cell contains 46
small thread-like structures called chromosomes, arranged in 23
pairs.
 22 pairs of chromosomes named autosomes
 1 pair chromosomes (X, Y)
 Male: XY
 Female : XX
 The length of each chromosome is divided into many small units
called genes.
 Genes code for different inherited physical characteristics,
including blood groups.
 Each gene has its own locus, along the length of the chromosome.

8. Allomorphic genes (Alleles)
 Each gene has its own place called locus along the length of the
chromosome
 Certain inherited characteristic can be represented by a group of
genes, and the locus can be occupied by only one of these genes.
Such genes are called alleles or allomorphic genes

11. Genotype Vs Phenotype
 Phenotype
 Physical expression of inherited traits,
 Determined by reacting red cells with known antisera
 Genotype
 Actual genes inherited from each parent
 Can only be inferred from the phenotype .
 Family studies are requiredto determine the actual genotype

12. • The genetic composition from a particular inherited characteristic is
called the genotype, and the way this can be seen is called
phenotype.
• Thus, if a person is group A (phenotype) his genotype could be either
AA or AO.

13. Table 1.1. The ABO phenotypes and their
corresponding genotypes
Phenotype Genotype
A AA, AO
B BB,BO
AB AB
O OO

14. Inheritance Pattern of Blood Group Antigens
 In most cases blood group antigens are inherited with co
dominant expression.
 The product of each allele can be identified when inherited
as a co dominant trait.
 If one parent passed on an A gene and the other parent passed
on a B gene, both the A and B antigens would be expressed
equally on the red blood cells.

15. RECESSIVE OR DOMINANT INHERITANCE PATTERNS
 Recessive allele
 only visible when paired with another recessive allele
 Is the loser
 Always overshadowed if a dominant allele is present
 Always written with lowercase letter
 Dominant allele
 Expressed even if it is paired with a recessive allele
 Always WINs over recessive
 Phenotype that shows up
 Always written with capital letter
…con’t

16. 16

17. HOMOZYGOUS AND HETEROZYGOUS INHERITANCE PATTERNS
• Homozygous
• 2 alleles for a given trait are the same (alleles on corresponding
positions of homologous chromosomes are identical)
• Genotypes are identical genes
• Example: BB or bb
• Heterozygous
• 2 alleles inherited are different (pairs of different alleles present on
corresponding positions of homologous chromosomes)
• Genotypes are different
• Example: Bb
…con’t

18. …con’t Punnet square
 Illustrates the probabilities of phenotypes from known or
inferred genotypes.
 Visually portrays the potential offspring`s genotypes or
the probable genotypes of the parents
B b
B BB Bb
B BB Bb