Use of avidin-biotin-peroxidase complex (ABC) in postembedding immunoelectron microscopy: detection of immunoglobulins in myeloma cells.

For the purpose of detecting immunoglobulins at the electron microscopic level, the avidin-biotin-peroxidase complex (ABC) technique was applied to ultrathin sections of the bone marrow obtained from patients with multiple myeloma. In this study, a low temperature embedding medium (Lowicryl K4M) was applied to avoid the loss of antigenicity. This electron microscopic ABC (EM-ABC) technique allowed the detection of cytoplasmic immunoglobulins in myeloma cells and provided fairly satisfactory ultrastructural preservation. However, nonspecific reaction product was seen in eosinophil granules possibly due to the close affinity of biotinylated antibodies for eosinophil granules. The EM-ABC staining is of definite value for detecting various antigens as well as immunoglobulins in biological specimens.