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.

T cell receptor alpha chain polymorphisms in multiple sclerosis.

Numerous studies have implicated the major histocompatibility complex (MHC) class II alleles, DR2 and DQw1, as multiple sclerosis (MS) susceptibility loci, however, the involvement of other loci is implied by twin studies and the relative lack of haplotype sharing for MHC. To evaluate the role that the TCR alpha chain genes may have in MS susceptibility, three variable (V) alpha polymorphisms were examined for associations in MS patients. Genotype and allele frequencies were compared to four different control groups: unaffected siblings and parents of the MS patients, patients with insulin-dependent diabetes mellitus (IDDM) and healthy unrelated Caucasians. No significant differences in allele and genotype frequencies at these three loci were observed in the MS population compared to the control groups. In addition, we analysed the distribution of haplotype sharing in affected sibling pairs. Among 30 informative families, there was no significant increase in haplotypes shared by affected siblings over that expected based on random segregation. Our results do not support suggestions that germline TCR alpha chain genes contribute to genetic susceptibility in MS.

Heterogeneity in multiple sclerosis: comparison of clinical manifestations in relatives.

Once diagnosed to have MS, relatives of persons who have been previously diagnosed frequently ask whether their disease course will follow that of their relative(s) with MS. The present study compared the following clinical manifestations of MS among 43 index cases and 47 of their relatives, all of whom were diagnosed to have MS and regularly attended the MS Clinic in Vancouver, British Columbia: (i) age of onset of MS, (ii) clinical course, (iii) lesion site(s) and (iv) initial symptom(s) of MS. The results from the present study are preliminary because of the small size of the study group. However, these data suggest that apart from possibly age of onset between sibling pairs, the clinical manifestations of MS are not correlated among relatives who are assessed according to the same methodology. This is significant for counselling newly diagnosed relatives of longstanding MS patients.