Biochemical analysis of variant HLA-B27 antigens

Biochemical analysis of HLA-B27 antigens from individuals that are HLA-ABC identical by serology but distinct in CML typing establishes that two types of HLA-B27 can be defined biochemically. The division of HLA-B27 into a W type and a K type by CML typing correlates perfectly with the biochemical data. HLA-B27 K type possesses a more basic isoelectric point than HLA-B27 W type. Neuraminidase digestions of immunoprecipitated HLA-A,B antigens establish that the difference in isoelectric point between HLA-B27 K and HLA-B27 W is not due to differences in sialic acid content.