Detection of cell-bound immunoglobulins by a radioisotopic micro-mixed hemadsorption reaction with technetium-99m-labeled erythrocytes.

The mixed hemadsorption (MHA) reaction detects antibodies reactive with cell surface antigens by means of antiglobulin-coated indicator erythrocytes. We have developed a radioisotopic modification which employs sheep erythrocytes (SRBC) that have been prelabeled with technetium-99m (99mTc), a high specific acitivity metastable gamma-emitter of short half life. The 99mTc MHA reaction was performed on human and murine cells cultured in Micro-test II plated with six replicate wells per serum dilution. Antibody activity in species-specific xenoantisera and mono- and polyspecific alloantisera was detected in high titer. The sensitivity of 99mTc micro-mixed hemadsorption was 2 times that of the visual assessment of mixed hemadsorption, 100 to 200 times that of the 125-I-mixed antiglobulin reaction and 500 to 1000 times more sensitive than indirect immunofluorescence. The assay system was applied successfully to confirm the species of origin of a panel of previously karyotyped human and mouse cell lines. Our results indicate that the 99mTc micro-mixed hemadsorption method is a rapid, sensitive, quantitative test for the detection of cell surface antigens and membrane reactive antibodies.