Expression of a shortened EDA molecule in an affected relative of P6. Sera from a pool of adult subjects with XLHED who all carry EDA null mutations (no EDA1 expression), from the grandfather of P6 and also from two healthy adults were investigated by immunoprecipitation with a mix of two anti-EDA monoclonal antibodies, EctoD2 and EctoD3, that both recognize the native C-terminal domain of EDA. Subsequent Western blotting with the antibody Renzo-2 recognizing the denatured C-terminal domain of EDA was performed. Increasing amounts of recombinant Fc-EDA were loaded onto the same gel as positive controls. The positions of molecular weight markers (in kDa) are indicated. HC and LC, heavy and light chains of the antibodies used for immunoprecipitation; EDA, processed soluble form of wild-type EDA; EDA Δ, shorter form of EDA in serum from the grandfather of P6. This experiment was conducted twice with similar results.