Plant and Mammalian Physiology

Experiment 4

Aim of the Experiment

To determine the blood group and Rh factor of an individual.

Introduction

Blood grouping is the classification of blood based on the presence or absence of two inherited antigenic substances on the surface of red blood cells (RBCs). The ABO and Rh are the major, clinically significant and the most important of all the blood group systems. The ABO blood group system was first discovered by Karl Landsteiner in 1900. The human ABO blood group system is divided into the following four major groups depending on the antigen present on the surface of their red blood cells:

1. “A” group

2. “B” group

3. “AB” group

4. “O” group

Table 1: ABO Blood Group System

The associated Anti A and Anti B antibodies usually belong to IgM class of immunoglobulins. The Rhesus system (Rh) is the second most important blood group system in humans. The most significant and immunogenic Rhesus antigen is the RhD antigen. The individuals carrying the Rh antigen are considered to have positive blood group whereas those individuals that lack this antigen are considered to have negative blood group.

Principle

The ABO and Rh blood grouping system is based on agglutination reaction. When red blood cells carrying one or both the antigens are exposed to the corresponding antibodies they interact with each other to form visible agglutination or clumping. The ABO blood group antigens are O-linked glycoproteins in which the terminal sugar residues exposed at the cell surface of the red blood cells determine whether the antigen is A or B. Blood group A individuals have A antigens on RBCs and anti-B antibodies in serum. Similarly, blood group B individuals have B antigens on RBCs and anti-A antibodies in serum. Blood group AB individuals have both A and B antigens on RBCs and neither anti-A nor anti-B antibodies in serum. Whereas, blood group O individuals have neither A antigens nor B antigens, but possess both anti-A and anti-B antibodies in serum. The Rh antigens are transmembrane proteins in which the loops exposed on the surface of red blood cells interact with the corresponding antibodies.

Materials required

Reagents: 70% Alcohol/ Spirit, Anti-A, Anti-B, and Anti-D.

Other requirements: Cotton, Slide.

Procedure

1. Dangle the hand down to increase the flow of blood in the fingers.

2. Clean the fingertip to be pierced with spirit or 70% alcohol (usually ring or middle finger).

3. With the help of the sterile lancet, pierce the fingertip and place one drop of blood in each of the cavities.

4. Add one drop of antiserum into each cavity as shown below:

5. Mix each blood drop and the antiserum using a fresh mixing stick.

6. Observe agglutination in the form of fine red granules within 30 seconds. Anti RhD takes slightly longer time to agglutinate compared to Anti A and Anti B.

Note: Proper care should be taken while disposing the lancet and mixing sticks.

Observation and Result:

Interpretation

• If agglutination is observed when blood is mixed with Anti A reagent, then the individual is said to have blood group “A”.

• If agglutination is observed when blood is mixed with Anti B reagent, then the individual is said to have blood group “B”.

• If agglutination is observed when blood is mixed with Anti A and Anti B reagent, then the individual is said to have blood group “AB”.

• If no agglutination is observed when blood is mixed with Anti A and Anti B reagent, then the individual is said to have blood group “O”.

• If agglutination is observed when blood is mixed with Anti RhD reagent, then the individual is said to have “+ve” Rh factor.

• If no agglutination is observed when blood is mixed with Anti RhD reagent, then the individual is said to have “-ve” Rh factor.

Questions

1. Where is the location of antibodies and antigen of all four blood groups?

2. Mention any other blood group other than A, B, AB and O blood groups?