Can genetic polymorphism of alpha-2-macroglobulin be detected by immunoelectrophoresis? A study using sera, plasma and joint fluids from patients with rheumatoid arthritis and controls.

The technique of immunoelectrophoresis (IEP) was used to examine polymorphism of the endopeptidase inhibitor alpha-2-macroglobulin (alpha 2M) by measuring its electrophoretic mobility. Examination of the variability of the method showed that a large intra- and inter-plate variation occurred (3.3 and 11.6%, respectively). It was also shown that alpha 2M from plasma moves significantly slower than that from serum and that the mobility of alpha 2M from plasma can be increased to that of serum by treatment with trypsin. Upon comparing sera, plasma and synovial fluids from a control group (normal subjects and patients with osteoarthritis) with a group of patients with rheumatoid arthritis, no difference in alpha 2M mobility could be demonstrated. It is concluded that genetic polymorphism of alpha 2M cannot be detected by the technique of IEP.