Zeta potentials, van der Waals forces and hemagglutination

Area of Science:

• Biophysics
• Immunology
• Cell Biology

Background:

• Erythrocyte zeta-potential is well-established.
• Van der Waals (Hamaker) coefficient of erythrocytes can now be determined.
• Interaction potential energy diagrams are crucial for understanding cell behavior.

Purpose of the Study:

• To elaborate net potential energy interaction diagrams for erythrocytes.
• To investigate erythrocyte interactions with and without sensitization by anti-D (Rh0) antibodies.
• To explain the mechanism of erythrocyte cross-linking by antibodies.

Main Methods:

• Calculation of net potential energy of interaction versus distance diagrams.
• Utilizing erythrocyte van der Waals coefficient and zeta-potential data.
• Modeling interactions for unsensitized and IgG-sensitized erythrocytes.

Main Results:

• Unsensitized erythrocytes approach to ~79 Å (surface) and ~180 Å (membrane), exceeding IgG valency distance.
• Unaided IgG anti-D (Rh0) antibodies cannot cross-link D (Rh0)-positive erythrocytes.
• IgG-sensitized erythrocytes approach to ~60 Å (Fc ends), enabling cross-linking by anti-IgG antibodies.

Conclusions:

• The physical constraints of IgG antibody size prevent direct erythrocyte cross-linking.
• Sensitization with IgG antibodies and subsequent addition of anti-IgG antibodies facilitates erythrocyte aggregation.
• Understanding these interactions is key for immunological and biophysical applications involving erythrocytes.