Immunofiksja

Immunofiksja, known in English as immunofixation electrophoresis (IFE), is a laboratory method used to identify and characterize monoclonal immunoglobulins in serum or urine. The technique combines electrophoretic separation of serum proteins with immunoprecipitation using monospecific antisera to determine the class and light-chain type of any monoclonal protein.

Procedure and interpretation: Proteins in a specimen are first separated by electrophoresis on an agarose gel. After separation, antisera specific for the heavy chains IgG, IgA, IgM and for the light chains kappa and lambda are applied in separate lanes. Immunoprecipitation occurs at the positions of the corresponding immunoglobulins, forming visible bands after washing and staining. A single discrete band in the appropriate lane indicates a monoclonal immunoglobulin of that class and light-chain type; multiple bands or a diffuse polyclonal pattern suggests polyclonal gammopathy or biclonality. Absence of reaction with a particular antisera can reveal immunoglobulin deficiency, such as light-chain–restricted gammopathies or heavy-chain deficiencies.

Applications: IFE is used to detect and characterize monoclonal gammopathies, including multiple myeloma, Waldenström macroglobulinemia, and monoclonal gammopathy of undetermined significance (MGUS). It provides information on the type of M-protein and helps monitor disease progression or response to therapy. It is more sensitive than standard serum protein electrophoresis for identifying monoclonal components and is commonly used alongside serum protein electrophoresis and immunoglobulin quantification.

Limitations: interpretation requires expertise; very low concentrations may yield inconclusive results. False negatives can occur with certain immunoglobulin deficiencies or complex samples. Specimens typically include serum and urine, and results may be complemented by other assays such as free light chain analysis.