Improved method for isolation of human IgM as a by-product.

The authors describe a simple method for isolating heterogeneous IgM from fraction I obtained as a by-product of the large scale fractionation of human plasma. The optimum circumstances of fractionation were determined and it was found that the majority of IgM is precipitated between 2 and 5% polyethylene glycol concentration and 1.1 and 1.8 M ammonium sulphate concentration. After a simple fractionation and gel filtration, a preparation of high purity can be obtained.