The antiglobulin reaction with native and enzyme-modified red cells

Area of Science:

• Immunology
• Hematology
• Biochemistry

Background:

• The antiglobulin test (IAT) is crucial for detecting antibodies against red blood cells (RBCs).
• Enzymatic modification of RBCs is known to enhance agglutination in certain serological tests.

Purpose of the Study:

• To investigate the effect of enzymatic modification on antibody binding and agglutinability of intact RBCs and RBC ghosts in the IAT.
• To elucidate the mechanisms underlying enzyme-induced enhancement of RBC agglutination.

Main Methods:

• Enzymatic modification (e.g., with proteases) of intact RBCs sensitized with anti-D antibody.
• Quantification of bound anti-IgG and anti-D using equilibrium binding assays.
• Immunoelectronmicroscopy of unsealed RBC ghosts.
• Assessment of RBC agglutinability in the antiglobulin reaction.

Main Results:

• Enzymatic modification of intact RBCs did not increase the equilibrium quantity of bound anti-IgG.
• RBC ghosts from enzyme-modified cells showed an increased ratio of anti-IgG to anti-D.
• Protease modification of intact cells decreased this ratio, possibly due to steric hindrance.
• Enzyme-modified cells exhibited enhanced agglutinability at comparable antibody levels.

Conclusions:

• Enzymatic enhancement of RBC agglutinability in the antiglobulin reaction is not directly correlated with increased antibody binding.
• Alterations in the biophysical properties of the RBC membrane likely mediate the enhanced agglutination.
• Findings contrast with previous studies on RBC ghosts, highlighting differences between intact cells and ghosts.