The frequency of HLA antigens is largely dependent upon the geographic location of the study population (Caruso et al., 2000, 2001). In this study, the homogeneous nature of the population from the north of Ireland, coupled with low levels of immigration due to the region's troubled past, has helped to alleviate some of the potential bias. The extremely polymorphic nature of the HLA complex creates a diverse range of haplotypes, thus lowering the power of the subsequent statistical analysis. Major limitations in the studies reported to date are the number of aged individuals available and complete background histories of health or ethnicity for study participants. It is proposed that HLA haplotype frequencies are often affected by environmental determinants such as a famine or an epidemic (Izaks et al., 2000). The evidence accumulated to date would suggest that there are a number of gender-specific HLA haplotypes associated with successful ageing in different geographic regions. To fully elucidate the role of the HLA in longevity, broad studies need to be performed integrating the many HLA typing laboratories throughout Europe to increase the number of aged samples and provide a strong foundation for meta-analysis.

In recent times, a plethora of studies have been performed in an attempt to fully resolve the role polymorphism of the HLA has in longevity. However, to date, a large body of conflicting data has been amassed (Caruso et al., 2000, 2001). The present study set out to specifically confirm the previously reported increase in the frequency of the HLA-A1, -B8, -DR3 haplotype (22.9 vs 8.7%) in aged males of the northern Irish population (Rea and Middleton, 1994).

Table 2: The observed frequencies of the most common HLA and TNF polymorphic haplotypes in healthy aged individuals and young controls

The observed allele and genotype frequencies for the two polymorphic markers of the TNF genes were analyzed for controls and aged individuals.

Acknowledgements

The authors wish to acknowledge The European Union for support under the aegis of European Union Concerted Action on the Molecular Biology of Immunosenescence (EUCAMBIS; Biomed 1 contract CT94-1209); and Immunology and Ageing in Europe (IMAGINE; QLK6-CT-1999-O2031). OA Ross was a recipient of a CAST Award jointly funded by the Department of Education and Learning (Northern Ireland) and the Histocompatibility and Immunogenetics Charitable Trust Fund.

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