Abstract
Summary
The sensitivity of the passive hemagglutination reaction was increased considerably by repeated freezing and thawing of antigen-coated erythrocytes. Cells were stabilized by pyruvic aldehyde followed by formaldehyde and then coated with antigen at low pH. After the desired HA titer was attained, the cells were stored in liquid nitrogen. Antigen-coated cells stored at 20° gradually deteriorated during the course of 18 months.
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