抄録
Serum from a male patient gave a unreliable result in two-site immunoenzymometric assay (EMA) kit, Enzymun Test CEA (Boehringer Mannheim) in which mouse monoclonal antibody for specific carcinoembryonic antigen (CEA) was used. Using other kits employing the same method using mouse monoclonal IgG also showed the simillar results; however, normal value of 2.1 ng/ml was obtained by conventional radioimmunoassay for CEA.
The interference was eliminated by either heating (70, 15min), or by adding mouse IgG, it's fragment Fab or Fc in reaction buffer.
Futhermore, patient's serum treated with antibody against the human IgM or treated with protein A gave decreased content of CEA.
In fractionation of patient's serum by Sephacryl S-300 gel chromatography, the CEA activity was detected on the first peak which contained predominantly IgM. In addition, mixed type cryoglobulins containing IgG and IgM were separated from the serum and CEA activity was also detected in it.
It is concluded that patient's serum IgM binds to mouse IgG and have the capability of interfering in immunoenzymo (radio) metric assay using mouse monoclonal IgG.
