Monoclonal autoantibodies that react with hormones also react with cells not containing those hormones.

Two immunoglobulin M monoclonal autoantibodies, PI-6 and AP-2, were found by immunofluorescence, hormone absorption, and enzyme-linked immunosorbent assay to react with insulin and GH, respectively. The same antibodies were also found to react with a variety of organs that do not contain those hormones. Absorption of PI-6 with insulin, but not with GH, and absorption of AP-2 with GH, but not with insulin, eliminated the capacity of these antibodies to react with all organs tested. It is concluded that these monoclonal antibodies are broadly reactive and recognize epitopes on more than one protein.