Separation of rubella IgM, IgA, and IgG antibodies by gel filtration on agarose.

Identification of the immunoglobulin classes of rubella antibodies is the only reliable tool for the diagnosis of a recent primary infection with rubella within 6-8 weeks of infection. Gel filtration permits the separation of IgM and IgA antibodies, both characteristic for a recent infection, from persistent rubella IgG antibody (which indicates pre-existing immunity). Gel filtration on agarose offers advantages over the other methods for separating immunoglobulin classes. Fractionation of specific rubella antibodies is important not only in all cases where a serum sample was taken too late and a rise of antibody titre missed, but also in cases with significant antibody rise to distinguish a secondary immune response after rubella reinfection.