Peroxidase Labeling of IgMs Fragment of ABO Blood Group Specific Mouse Monoclonal IgM

A method for peroxidase labeling of the monomeric subunit (IgMs) of ABO blood group specific mouse monoclonal IgM is described. IgM was purified from a commercial monoclonal anti-B blood grouping reagent by a combination of salt precipitation, euglobulin precipitation, and gel filtration. IgM was mildly reduced with L-cysteine to yield SH-bearing IgMs. Finally, IgMs was conjugated to horseradish peroxidase, into which SH-reacting maleimide groups had been introduced using N-succinimidyl 6-maleimidohexanoate, through the selective reaction between SH of IgMs and maleimide groups of peroxidase.