Immunoglobulines monoclonales : méthodes diagnostiques en 2011

A monoclonal gammopathy is charaterized by a selective increase of a single serum immunoglobulin due to an only dysregulated clone of B lymphocytes. This monoclonal component is composed of either only one heavy and one light chains, or of isolated light chains of only one isotype, or in particular instances of fragmented heavy chains of only one isotype. Monoclonal immunoglobulins may arise apart from malignancies. The demonstration and characterization of monoclonal immunoglobulins needs a linked serum and urine analysis. Detection of monoclonal component will not be done by a sole biological test, but by combining in different maners some of these listed methods: agarose gel electrophoresis, immunoelectrophoresis and/or immunofixation, capillary electrophoresis with immunosubstraction, immunoselection, quantification of immunoglobulins and of free light chains and characterization of cryoglobulinemia. The analysis of the results leading to the diagnosis of monoclonal immunoglobulin is still a matter of difficulty because in some clinical occurrences (light chain myeloma, cryoglobulinemia,…) the available methods have to be performed in the right order. A skillful methodological and biological experience is needed to conduct the right sequence of biological tests always after full knowledge of the patient's clinical status.