Immunoglobulin heavy chain variable region polymorphisms and multiple sclerosis susceptibility.

In addition to the major histocompatibility complex (MHC), genetic susceptibility in multiple sclerosis (MS) appears to be influenced by other loci. A recent study has identified a population association with an immunoglobulin heavy chain variable region polymorphism in the VH2-B5 family, with both familial and sporadic MS patients. We have repeated this association study in a second MS patient group and used two ethnically and geographically matched control groups and the MS patients' unaffected sibs for comparisons. The VH2-B5 polymorphism was found to be over-represented in MS patients when compared to all three control groups. This VH2-B5 association was stronger when the MS patient data were combined with data from our previous study. To further explore the implications of this population association, MS sibships were analyzed for haplotype sharing by identity by descent (IBD) for VH2 and VH3f gene segment polymorphisms. The distribution of haplotype sharing did not differ from that expected based upon random segregation. The data are consistent with the IGVH locus exerting a minor effect perhaps by interacting with other loci to influence MS susceptibility or with genetic heterogeneity and a role for this complex in a subgroup of patients.