Beta-2 globulins

The fourth electrophoresis band, carrying complement proteins and beta-2 microglobulin.

It sits next to the gamma band, so its shape is part of how a laboratory judges whether the gamma region is normal.

The individual value carries little on its own -- what a laboratory reads is the shape of the whole trace, including whether anything unusual sits between this band and gamma. Some labs merge beta-1 and beta-2.

Worth reviewing as part of the whole electrophoresis rather than alone.