Abrogation of baboon natural xenoantibody to pig splenocytes by DL-penicillamine.

Natural xenoantibodies are believed to be IgM in nature and are known to play a critical role in the hyperacute rejection of distantly related xenografts. The purpose of this study was to determine whether the reducing agent DL-penicillamine could inactivate baboon natural xenoantibodies to pig splenocytes. Pooled baboon serum was treated with varying concentrations of DL-penicillamine over different lengths of time and a complement-mediated cytotoxicity assay was used to determine the reactivity of baboon natural xenoantibodies to pig splenocytes. A whole-cell ELISA assay was used to assess the binding of both IgG and IgM xenoantibodies to pig splenocytes. In addition, DL-penicillamine-treated serum was dialyzed to assess its potential clinical application. These in vitro experiments indicate that both IgM and IgG baboon natural xenoantibodies bind to pig splenocytes, but only IgM xenoantibody is cytotoxic. The binding of baboon natural IgM xenoantibody can be eliminated, and the cytotoxicity of IgM xenoantibody markedly reduced by DL-penicillamine treatment despite continued binding of IgG xenoantibody to pig splenocytes. In addition, DL-penicillamine can be dialyzed, suggesting that it may be an efficacious clinical treatment, the toxicity of which can be regulated with hemodialysis.