A new class of immunoglobulin in human serum.

A new class of normal immunoglobulin corresponding to a myeloma protein (myeloma-IgND), which fails to react with specific antisera to IgA, D, G and M (Johansson and Bennich, 1967) was detected in serum from sixty-two blood donors using a radio-immunosorbent technique (Wide and Porath, 1966). IgND in normal sera corresponds to myeloma-IgND in Ouchterlony gel diffusion analysis. Isolated IgND gave a reaction of identity with myeloma-IgND in Ouchterlony gel diffusion analysis. The concentrations of IgND in 93·5 per cent of the samples was within the range of 100–700 ng/ml. Normal levels of IgND were found in four samples apparently lacking IgA and/or IgD as determined by single radial immunodiffusion. Elevated levels of IgND were found in four samples one of which was from a subject with previously undiagnosed extrinsic asthma. It is concluded that myeloma-IgND represents a new class of human immunoglobulin.