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The Effect of Enzymatic Release of Sialic Acid from Human Erythrocytes on Rh Agglutinations¹

From the Wadley Research Institute and Blood Bank and the Graduate Research Institute of Baylor University, Dallas, Texas

Abstract

NANA is released from red cells when they are treated with enzymes (trypsin, papain, ficin, bromelin and neuraminidase) which render them specifically agglutinable by incomplete Rh antisera. There is a progression in NANA release and serologic score as a function of enzyme concentration. However, the serologic score attained for a given quantity of NANA released varies with the genotype of the cell. In attempting to define the minimum NANA release consistent with agglutinability, it was found that for trypsin treatment liberation of 0.11 µmole NANA/10¹⁰ RBC gave no agglutination while release of 0.25 µmole did. A narrower range may be specified for neuraminidase in that release of 0.21 µmole NANA/10¹⁰ RBC gave agglutination with two of three anti-D sera, but liberation of 0.14 and 0.17 µmole failed to do so. Since proteases bind to the red cell, it was determined that about 35% of the NANA liberated may be released by that fraction of enzyme (papain) which is firmly bound to the cell. The general features of the reaction by which enzymes produce the serologic effect may be summarized as follows: 1) Proteases producing the serologic effect have common specificity. 2) Proteases bind to the red cell but must be catalytically active. 3) Neuraminidase is the only nonprotease known to produce this effect. 4) NANA is released in a manner correlating with serology. 5) This release is consistent with the decrease in RBC charge and -potential, which may be the ultimate factor determining the appearance of agglutination.

Footnotes

¹ This work was supported by Grant AM 02612 from the National Institutes of Health, United States Public Health Service.