A serum protein affecting the regulation of the immune system.

A thermostable alpha 2 globulin inhibiting the immunoglobulin/anti-immunoglobulin reaction was demonstrated working with subacute sclerosing panencephalitis (SSPE) and control serum IgG. This protein was isolated from SSPE and normal human blood, it inhibits the immunoglobulin/anti-immunoglobulin reaction but no other antigen/antibody reactions when applying different immunochemical methods such as nitrocellulose immunofixation, 2 site immunoradiometric assay, solid phase radioimmunoassay in coated cups. This was demonstrated, working on the one hand with measles virus strain Edmonston or SSPE virus strain D.R. and SSPE serum and on the other hand with IgG from SSPE and control serum. This alpha 2 globulin, an inhibiting protein, appears to be related to "normal immunosuppressive protein".