Electrical properties of the red blood cell membrane and immunohematological investigation

Abstract

Hemagglutination is widely used in transfusion medicine and depends on several factors including antigens, antibodies, electrical properties of red blood cells and the environment of the reaction. Intermolecular forces are involved in agglutination with cell clumping occurring when the aggregation force is greater than the force of repulsion. Repulsive force is generated by negative charges on the red blood cell surface that occur due to the presence of the carboxyl group of sialic acids in the cell membrane; these charges create a repulsive electric zeta potential between cells. In transfusion services, specific solutions are used to improve hemagglutination, including enzymes that reduce the negative charge of red blood cells, LISS which improves the binding of antibodies to antigens and macromolecules that decrease the distance between erythrocytes. The specificity and sensitivity of immunohematological reactions depend directly on the appropriate use of these solutions. Knowledge of the electrical properties of red blood cells and of the action of enhancement solutions can contribute to the immunohematology practice in transfusion services.

Keywords: Agglutination; Erythrocytes; Optical tweezers; Zeta potential.

Figure 1

Representation of the hemagglutination reaction. Blood group antigens and antibodies form a clumping of erythrocytes (modified from Parslow et at., 2004)⁽⁵⁾

Figure 2

Forces involved in antigen-antibody binding. Hydrophobic forces and van der Waals can be formed when antigens and antibodies are close to each other. Electrostatic interactions and hydrogen bonds do not require the antigen and antibody to be close (modified from Abbas & Lichtman, 2005⁽³⁾

Figure 3

Where k₁ and k₂ are the rate constant for the forward, and reverse reactions respectively. [Ag], [Ab] and [AgAb] are the concentration of Ab, Ag and combined product AgAb, and K is the equilibrium or association contant.⁽⁷⁾

Figure 5

Schematic representation of zeta potential. Erythrocytes (negative charges) in suspension causing a rearrangement of charges through the formation of two ionic layers that generate a electric potential difference between them, called the Zeta potential (Modified from Pollack & Reckel, 1977 and Rouger & Salmon, 1981).(1,13)

Figure 6

Equation for zeta potential

Figure 7

Segment structure of the molecule of dextran

Figure 4

The minimum distance for two red blood cells with IgG and IgM molecules to bind (scale 100Å) (Modified from Van Oss & Absolon, 1983).₍₄₎