There are no sex-related differences in HLA-DR allele fre- quencies in control populations, a fact well established and directly verified here for the Paris and Strasbourg groups (P > 0.7 in a c 2 test comparing the distributions between genders in a group totalling 1302 individuals). The allele frequency distribu- tions for five groups, comprising the controls and four longevous groups, are shown in Table 2. A c 2 test with the corresponding contingency table detected a significant disparity in the allelic distributions (P < 0.005, c 2 = 80.1 for df = 48). The three largest contributions to the c 2 come from DR11, DR7 and DR13 alleles, respectively. Indeed, striking differences appear at first sight. DR7 allele frequency was 14% in controls, as compared with 21.2% and 23.1% in VIE and SIB males, respectively, which is higher than in any regional control group. DR11 allele frequency, as compared with 12.8% in controls, was 23.4% in female SIB, which is also higher than in any region of France. Finally, DR13 allele frequency was 12.6% in controls as compared with 17.4% in male and female centenarians, once again a higher frequency than in any of the regions. Comparisons of DR7, DR11 and DR13 frequencies among controls and longevous groups are visualized in the histograms of Figure 1. These three alleles seemed to display diverse influences on longevity: whereas DR7 was increased in long-lived men, whether isolated centenarians or members of sibships, DR11 was increased only in long-lived women belonging to sibships and DR13 was increased in centenarians of both genders. There is, within the SIB group, a subset of individuals who have also become centenarians: 16 men and 50 women. The frequencies of DR7 in male SIB-centenarians and of DR11 in female SIB-centenarians are, respectively, 25% and 22%, which strengthens the group specificity of these alleles’ influences on longevity.

In this study, we present data obtained by genotyping at the DNA level, gathered on two longevous populations selected according to different criteria: centenarians and long-lived siblings.

RESULTS

Control and long-lived populations defined

A total of 325 centenarians (VIE group, individuals in their 100th year or beyond) and 229 nonagenarian siblings (SIB group, see Materials and Methods for inclusion criteria) from the Chronos Collection were genotyped for HLA-DRB1 alleles. The follow- ing work bears on the 13 generic DRB1 alleles, hereafter simply named after the generic DR specificities, e.g. DR3. Genotypes from adult blood donors (aged 20–60) were gathered from seven regions of France, totalling 2950 controls. Allele distributions for the different populations are given in Table 1. Although fluctuations of certain allele frequencies do occur in several regions, there was no significant overall heterogeneity among the distributions in control populations (P > 0.4 for a c 2 test, df = 84). Therefore, genotypic data for controls were pooled in all subsequent calculations. In contrast, a comparison between centenarians and pooled controls revealed a significant hetero- geneity in the HLA-DR allele distributions (P < 0.05, c 2 = 24 for df = 12). Four sets of longevous individuals were therefore distinguished: male or female centenarians (VIE), male or female nonagenarian siblings (SIB).

Table 1. HLA-DRB1 allele frequencies in different regions of France

Allele Paris Amiens Limoges Poitiers Montpellier Marseille Bretagne Strasbourg Total n = 509 n = 43 n = 64 n = 558 n = 300 n = 108 n = 150 n = 1218 n = 2950 DR1 12.7 11.6 12.7 11 10.8 7.4 12.7 11.5 11.5 DR3 11.7 16.3 11.9 10 10.2 13.3 11.7 10.8 11.0 DR4 11.7 15.1 8.7 13.4 16.8 11.7 19.7 12.5 13.3 DR7 12.8 8.1 14.3 14 16.8 13.3 15.3 13.9 14.0 DR8 2.65 1.2 6.3 2.2 1.8 3.9 3 3.1 2.8 DR9 0.3 0 3.2 0.7 0.6 1.1 1 0.8 0.7 DR10 0.9 1.2 0.8 1 0.6 1.5 0.3 0.7 0.8 DR11 14.2 16.3 11.1 13.4 13.8 13.8 4.3 13.3 13.1 DR12 0.7 2.4 2.4 1.8 1.8 0.5 0 2 1.6 DR13 13.5 12.8 12.7 15 9.6 13.8 9.7 12.5 12.8 DR14 4 1.2 4 3.2 4.2 5.8 3.7 3.9 3.8 DR15 12 5.8 8.7 10.7 12.0 10.8 18.3 13.2 12.4 DR16 3 7 3.2 3.4 1.2 3.2 0.3 1.7 2.3

Subjects were genotyped at the DNA level in all groups save Marseille and Montpellier, for which results were from serotyping. For these last two groups, allele frequencies were computed from antigenic frequencies, whereas they were directly provided for other groups.

Table 2. HLA-DRB1 allele frequencies among controls and long-lived groups

Allele Controls Female centenarians Male centenarians Female siblings Male siblings n = 2950 n = 259 n = 66 n = 77a n = 86b DR1 11.5 9.1 14.4 9.1 8.0 DR3 11.0 10.8 8.3 11.0 13.4 DR4 13.3 13.1 12.9 10.7 10.4 DR7 14.0 15.0 21.2 15.6 23.1 DR8 2.8 3.3 1.5 0.6 4.1 DR9 0.7 1.0 0.8 0.0 1.7 DR10 0.8 0.8 0.8 1.6 1.2 DR11 13.1 11.6 6.8 23.4 11.7 DR12 1.6 1.3 0.0 0.6 0.6 DR13 12.8 17.4 17.4 13.6 11.0 DR14 3.8 3.7 1.5 1.0 3.2 DR15 12.4 9.5 10.6 9.2 8.4 DR16 2.3 3.5 3.8 3.5 3.2

When two or more nonagenarians of the same sex were genotyped in a family, all genotypes were taken into account and weighed so that in every case two alleles per family were counted. All longevous individuals were genotyped following the same procedure. aNumber of independent sibships, comprising 121 SIB females. bNumber of independent sibships, comprising 108 SIB males.

Table 3. Homozygosity in control and longevous groups

Homozygotes are given for two control groups for which individual genotypes were available. Adult populations are in Hardy–Weinberg equilibrium. The slight departure from Hardy–Weinberg equilibrium in centenarians does not reach statistical significance. However, the rate of homozygosity is significantly higher in centenarians than in controls (P < 0.01 for this one comparison).

Homozygosity in centenarians

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