Blood groups

BLOOD GROUPS

Department of Physiology

IMPORTANCE OF BLOOD GROUPING:

• Practical importance of blood grouping includes:
• Blood transfusion
• Paternity disputes
• Medicolegal use eg blood stain on clothes
• Association with susceptibility to disease:
• Blood group O: more susceptible to peptic ulcers

Blood group A : more susceptible to carcinoma of stomach

THE HISTORY OF BLOOD TRANSFUSION

• In 1901 Karl Landsteiner published his work
• He discovered the ABO blood group system by mixing blood samples from his colleagues
• Later, it was also noted that:
• Some people were given blood with no reaction
• While others received blood there were some reactions even death

Landsteiner and Weiner discovered Rh system (1940) The best known groups are the ABO & Rhesus systems are of great importance in blood transfusion today

ABO BLOOD GROUPS

Depending on the presence or absence of A & B antigens, humans can be divided into A, B, AB & O groups The antibodies reacting with the:

• Antigen A is called antibody A (alpha)
• Antigen B is called antibody B (beta)
• Antigen O is not antigenic and has no corresponding antibodies
• The prevalence of ABO blood groups among the Europeans:

TYPE FREQUENCY (%)

O 47

A 41

B 9

AB 3

OTHER BLOOD GROUPS

• In addition to the ABO & Rh blood groups are:

M, N, P, Lutheran, Kell, Duffy, Kid, Diego etc etc These blood groups have demonstrable antigens but the corresponding antibodies in the plasma are generally not present.

LANDSTEINER’S LAW

The Law states that:

“If an antigen (agglutinogen) is present on the Rbc of an individual, the corresponding antibody (agglutinin) must be absent and that IF an antigen is absent on the Rbc of an individual, corresponding antibody must be present in the plasma”

LANDSTEINER’S LAW

• Blood groups, antigens & antibodies according to Landsteiner’s law:
• Blood group Antigens Antibodies

O NO A & B

A A B

B B A

AB A & B NO

FORMATION OF ANTIBODIES

The specific blood group antibodies (Antibodies A & B) are absent at birth, but they appear and reach a maximum concentration by the age of 10 years.

INHERITANCE OF ABO BLOOD GROUP

• ABO blood groups are inherited in accordance with Mendelian principle:

by a means of 3allelic genes A, B, and O.

The A & B genes are co-dominant while O gene is functionless ie has no demonstrable product

GENETIC INHERITANCE OF ABO BLOOD GROUP

• From

B B BB B

BLOOD GROUPING

Before blood transfusion, the patient’s (recipient) and donor’s blood group are determined.

Anti A Anti B Blood Group

Cells 1 – – O

Cells 2 + – A

Cells 3 – + B

Cells 4 + + A & B

NB: + Reaction & – No reaction

THE RHESUS (Rh) BLOOD SYSTEM

The Rh System derives its name from the findings that the antibody produced in the rabbit by injection of Rbc from the Rhesus monkey would:

• Agglutinate 85% of human cells (Rhesus Positive)
• The remaining 15% could not agglutinate (Rhesus Negative)
• This type of antibody was also found in:
• Some people who had transfusion before.

Mothers who had given birth to a child with Haemolytic Disease of the Newborn (HDN) People who were originally labelled as Rhesus positive (Rh + ve) have actually the D antigen on their Rbc’s membrane

RHESUS CONT.

Similar to D antigens are C & D antigens, but are not clinically important D antigen is much more potent ie it stimulate antibody production with greater frequency than any other Rh antigen

CLINICAL SIGNIFICANCE OF Rh FACTOR

• Although there are no natural antibody Rh(D)
• These antibodies can however develop in two ways:
• When an Rh Negative person is given Rh positive blood.

First transfusion of Rh+ve into Rh-ve there will be no reaction However subsequent transfusion of Rh+ve of blood causes haemolysis of transfused blood due to Anti Rh (D)

CLINICAL SIGNIFICANT OF Rh CONT.

• When an Rh –ve mother gets Rh +ve fetus from a Rh +ve father.

Thefirst pregnancy will have no reaction However, subsequent pregnancies with Rh+ve fetus result into Haemolytic Disease of the Newborn (HDN)

THANK YOU