Mechanism of Enhancement of Blood Group Antibody Reactions in Low Ionic Strength

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Abstract
When the ionic strength of blood samples is reduced, blood group antibodies bind to red blood cells that lack the corresponding antigen. Upon normalization of the ionic strength, the antibodies elute into the supernatant fluid. We compared, in semiquantitative terms, this nonspecific and reversible binding of various blood group antibodies. Studies with anti-CD antibodies showed that the nonspecific binding increased when the ionic strength was progressively lowered. In 1/10 normal ionic strength, practically all of a high-titer anti-CD antibody bound to Rh(D)-negative RBC (phenotype ce). The majority of the other antibodies studied (anti-C, -c, -Fya, -Fyb, and -S) behaved similarly in 1/10 normal ionic strength, but the binding of some (anti-E, -s, and -Jka) was, at times, less complete. Most examples of anti-K antibodies, however, demonstrated very poor nonspecific binding to K-negative RBC in low ionic strength (LIS). The authors propose that the augmentation of specific blood group antibody reactions in LIS is the direct result of this nonspecific binding, and that the failure of these conditions to support the nonspecific binding of anti-K antibodies might explain the lack of augmentation (and, at times, even the impairment) of the reactions of anti-K with its antigen.