ISOELECTRIC-FOCUSING OF MONOCLONAL IMMUNOGLOBULIN-G, IMMUNOGLOBULIN-A AND IMMUNOGLOBULIN-M FOLLOWED BY DETECTION WITH THE AVIDIN-BIOTIN SYSTEM

The sera of 49 subjects with IgG, IgA or IgM benign monoclonal gammopathy-components were examined by agarose gel isoelectric focusing followed by Coomassie Brilliant Blue R-250 staining as well as avidin-biotin amplified double-antibody peroxidase labeling after nitrocellulose blotting. IgG components gave 2-10 distinct bands within the isoelectric point (pI)-range of pH 6.5-9.5. IgA-components were focused into 10-15 bands with pI-values of pH 4.5-6.5 and the IgM-components gave 1-2 fractions within the pI-range of pH 4.5-6.5. The avidin-biotin peroxidase complex (ABC) technique exhibited some tendency to non-specific labeling related to the avidin-biotin component and depending on the relative amounts of the individual proteins. The method has a definite potential for the visualization of submicrogram quantities of immunoglobulins blotted to nitrocellulose membranes after isoelectric focusing.