The serum from a 66 year-old woman (F.T.) with IgA-kappa multiple myeloma displayed two distinct IgA-bands at α₂ region on a conventional cellulose-acetate membrane electrophoresis. Two molecular forms of IgA, a high molecular weight IgA (P₁) and a low molecular weight IgA (P₂), each of which corresponded to two bands on the cellulose-acetate membrane, were separated from the serum of the patient by gel-filtration. Their molecular characteristics, subclasses and allotypes were investigated by electrophoresis under reducing or non-reducing conditions, reactivity with an IgA 1-specific lectin, jacalin, and susceptibility to an IgA 1-protease. These two IgAs (P₁ and P₂) had the same isotype and kappa chains, and the electrophoretic mobility of P₁ was converted into that of P₂ on conventional agarose gel electrophoresis after reduction of disulfide bonds. They lacked reactivity with jacalin and were resistant to IgA 1-protease. Thus, both IgAs were identified to be IgA2 subclass with different molecular forms. Upon SDS-PAGE under non-reducing condition, both IgAs released dimeric light chains. This indicates that both IgAs lacked disulfide bonds between heavy and light chains, but had those between two light chains, a characteristic stractural feature of IgA2, A2m (1) allotype. It was thus concluded that the patient was IgA myeloma of IgA2, A2m (1) allotype with two molecular forms. This would be the first report describing the precise analysis of the IgA2, A2m (1) myeloma protein from Japanese patient.

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M-components of immunoglobulin in the sera have been classified by immunoelectrophoresis, a delicate and time consuming procedure. A new method, affinity absorbed electrophoresis, was described with advantages of easy, rapid (40min) and economical procedure. Instead of antisera, Omnibind A/G, Jacalin and dithiothreitol as specific reagents for IgG, IgA and IgM, respectively, were taken into three microtips and lyophilized. Each 10μl sera was taken into these tips and then applied for automatic electrophoresis. Either disappearance, or decreased concentration, or more rapid or slower migration of M-component than original was estimated as positive reaction with the reagents. Then the heavy-chain classes of M-component were discriminated. Three hundred eighty-four M-components out of 416 sera (92.3%) were easily identified. Corresponding patterns of the other 32 sera containing IgD, IgA2, L-chain and heavy-chain M-component, respectively, were also described, but not distinctive. However, affinity absorbed electrophoresis is good to identify M-component class as a routine analysis.

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