Rabbit IgM: its isolation in high yield by a convenient procedure using serum from trypanosome-infected animals.

Rabbit sera contain little IgM. This is a major obstacle for its isolation. However, levels of IgM up to 10 mg/ml are found in rabbits infected with living trypanosomes. A simple procedure, involving gel filtration, standing in the cold, and agarose block electrophoresis is described which allows the isolation of IgM from these sera in 60% yield, with a purity of better than 90%.