BoLA Class II Iso-electric focusing

Isoelectric focusing of immunoprecipitated class II antigens clearly demonstrated class II polymorphism at the protein level for the first time (example gel). Although fraught with problems of standardization between labs, the method was an important early tool for correlating expressed polymorphism with RFLPs detected at the DNA level. Recently, discrimination of the products of the DQ and DR genes has been achieved using locus-specific mAb. Correlations between alleles detected by 1D-IEF typing and those identified using other typing methods are generally good. In all, 12 IEF variants (DRBF designations) were accepted in the 5th BoLA workshop , shown schematically here.

The international workshops have demonstrated conclusively that 1D-IEF for DRB 3 alleles underestimates expressed polymorphism as judged against PCR-RFLP typing (see 5th workshop report). This is not surprising given the essential limitation of the method, i.e. only charge variants can be detected, leaving undetected changes that cause silent or conserved amino acid substitutions.

This text was taken from Lewin 1996, with permission from the publisher CRC Press.