Preparation of conjugated erythrocytes for long term use in hemolytic plaque assays, complement fixation studies, or passive hemagglutinations: a comparative study of several methods.

A variety of conjugation procedures, with and without glutaraldehyde stabilized erythrocytes, was employed to couple human IgG to sheep erythrocytes. The efficiency of conjugation, the recovery of cells, and the extent of labeling are noted. These conjugated erythrocytes were then tested for suitability in the hemolytic plaque assay, in a passive hemagglutination test, in a complement assay, and in the detection of rheumatoid factor. Although several methods were useful in a variety of situations, it was found that conjugation using a water soluble carbodiimide (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide) at low temperature (4 degrees C) produced a uniformly acceptable product that was stable and reproducible over a seven week period. The use of this method for a diversity of antigens or haptens is discussed.