The distribution, age effects and disease associations of HLA antigens and other blood group markers in a random sample of an elderly population

Ageing and disease

The concept of disease has a long and changing history, and has accumulated implications that can be unhelpful. The traditional distinction made between 'normal ageing' and 'disease' identifies research into the impact of an ageing population as having arisen within clinical medicine with its tradition of dichotomous thinking. The model is inappropriate for clinical practice among the elderly where diseases should be relegated to the role of mechanisms producing functional problems, and where interventions may not be of the traditional medical form. In this context the concept of 'normal ageing' can act as an excuse for inaction. For gerontological research the basic model is of the interaction between extrinsic and intrinsic factors. We lack the means at present to identify intrinsic processes, although they may be found among the residual ageing effects when extrinsic processes have been excluded. Intrinsic ageing processes may ultimatedly be identifiable on the basis of biological theory. Until this is possible we should study age-associated phenomena without prematurely conceived notions about their origins.

Immunogenetics of longevity. Is major histocompatibility complex polymorphism relevant to the control of human longevity? A review of literature data

Literature data suggest that human longevity may be directly correlated with optimal functioning of the immune system. Therefore, it is likely that one of the genetic determinants of longevity resides in those polymorphisms for the immune system genes that regulate immune responses. Accordingly, studies performed on mice have suggested that the Major Histocompatibility Complex (MHC), known to control a variety of immune functions, is associated with the life span of the strains. In the last 25 years, a fair number of cross-sectional studies that searched for the role of HLA (the human MHC) genes on human longevity by comparing HLA antigen frequencies between groups of young and elderly persons have been published, but conflicting findings have been obtained. In fact, the same HLA antigens are increased in some studies, decreased in others and unchanged in others. On the whole, that could lead us to hypothesize that the observed age-related differences in the frequency of HLA antigens are due to bias. In our opinion, this hypothesis is real for most studies owing to major methodological problems. However, some studies that do not meet these biases have shown an association between longevity and some HLA-DR alleles or HLA-B8,DR3 haplotype, known to be involved in the antigen non-specific control of immune response. Thus, HLA studies in man may be interpreted to support suggestions derived from the studies on congenic mice on MHC effects on longevity. However, in mice the association may be by way of susceptibility to lymphomas whereas, in human beings, the effect on longevity is likely, via infectious disease susceptibility. Longevity is associated with positive or negative selection of alleles (or haplotypes) that respectively confer resistance or susceptibility to disease(s), via peptide presentation or via antigen non-specific control of the immune response.

HLA, aging, and longevity: a critical reappraisal

Despite a large number of studies, available data do not allow at present to reach definitive and clear conclusions on role of HLA on longevity, owing to major methodological problems, such as serological and molecular typing of different loci, insufficient sample sizes, different inclusion criteria and age cut-off, inappropriate mixing of data referred to people from 58 to over 100 years of age, inappropriate control matching, and neglected consideration of sex-related effects and the different genetic make-up of studied populations. However, within this confused scenario, some data emerge. First, two studies that do not fit the biases above discussed show that some HLA alleles are associated with longevity. However, some of these alleles may confer an increased risk to undergo a variety of diseases. Second, longevity may be associated with an increased homozygosity at HLA loci. Third, an intriguing association between longevity and the 8.1 ancestral haplotype (AH), which has been proven to be associated with a variety of immune dysfunctions and autoimmune diseases, apparently emerges. This association appears to be a sex-specific (males) longevity contributor, and it is particularly interesting, taking into account that a type 2 (early infancy) --> type 1 (adulthood) --> type 2 (aging) shift of cytokine profile occurs lifelong, and that individuals bearing this haplotype show a type 2 immune responsiveness (note that type 1 cytokines mainly enhance cellular responses, whereas type 2 cytokines predominantly enhance humoral responses). On the whole, the (sex specific) association of longevity with alleles or haplotypes of several genes related to risk factors for a variety of diseases (cardiovascular diseases, cancer), including HLA alleles and haplotypes, is not unexpected on the basis of previous studies on the genetics of longevity in centenarians. This association can be interpreted under the perspective of a well known evolutionary theory of aging (antagonistic pleiotropy). This theory predicts that the same gene (or allele or haplotype) can have different roles (positive or negative) in different periods of the life span. Thus, the 8.1 AH should exert a positive effect during the infancy and aging but not in adulthood, when, indeed it is associated to susceptibility to a variety of diseases.

The effect of geographic origin on the frequency of HLA antigens and their association with ageing

The association between HLA antigens and ageing is not clear. Ageing in women was associated with B40 and DR5 in a recent study, but other studies yielded conflicting results. In none of the studies, however, did the young and elderly samples originate from the same homogeneous population. Homogeneity is dependent on geographic origin. The aim of this study was to investigate whether differences in geographic origin between age groups could explain the age-associated differences in the frequencies of B40 and DR5. The authors used the new design of a 'birth-place-restricted comparison' in which the origin of all subjects was ascertained. The total study population comprised 1010 young women aged 25-40 years and 660 elderly women aged 85 years and older. The 'birth-place-restricted comparison' included 66 young and 285 elderly women from one geographic area (Leiden, the Netherlands). Men were not included because ageing in men was not associated with HLA antigens in a recent study. In the total population, the frequency of B40 in young women of different origin varied between 16 and 28%, and the frequency of DR5 between 11 and 23%. Similar differences were observed in the elderly women. In the 'birth-place-restricted comparison', the frequency of B40 was 15% in the young women and 11% in the elderly women (difference 4%, 95% confidence interval, -5 to 13%). The frequency of DR5 was 20% in the young women, and 28% in the elderly women (difference 8%, 95% confidence interval, -4 to 19%). Thus, marked differences in HLA antigen frequency were found between populations of various geographic origins. Definition and ascertainment of the target population are therefore necessary in genetic studies of ageing. In such a 'birth-place-restricted comparison', the authors confirmed that ageing in women was negatively associated with HLA-B40 and positively associated with HLA-DR5.

Is the phenotypic combination A1B8Cw7DR3 a marker for male longevity?

OBJECTIVE

To study whether individual Human Leucocyte Antigens (HLA) at the HLA 1 or 11 loci or the phenotypic combination A1B8Cw7DR3 were associated with longevity.

DESIGN

Direct comparison of the > 90-year-old subjects with a control group.

SETTING

Northern Ireland population with little migratory mobility.

SUBJECTS

The > 90-year-old group (79 females, 38 males) was compared with a control group consisting of 150 unrelated blood donors (81 females, 69 males).

MEASUREMENTS

Human Leucocyte Antigen (HLA) Class 1 typing was carried out on 117 nonagenarians (mean age 93.7 years) and 150 younger controls (mean age 33.7 years) using conventional serological methods; HLA DR typing was carried out on 102 of the 117 > 90-year-old subjects, together with the 150 control subjects, and performed using restriction fragment length polymorphisms. The frequency of the phenotypic combination A1B8Cw7DR3 was measured in both groups.

RESULTS

There were no significant differences in the HLA antigen frequencies between the very elderly groups and the younger subjects at the A, B, C, and DR loci. The phenotypic combination A1B8Cw7DR3 was significantly increased (X3) in nonagenarian men compared with young men but not between elderly women and young women. There was a trend for increased representation of this phenotype in elderly men compared with women of the same age.

CONCLUSIONS

The frequency of the supratype A1B8Cw7DR3 was significantly increased in very elderly men but not in elderly women. Since this phenotypic combination has been associated with immune surveillance and/or hyperactivity in Caucasians, there is the suggestion that it could influence longevity through immune mechanisms but that sex differences may exist in its influence and expression.

Longevity and heredity in humans. Association with the human leucocyte antigen phenotype

Several arguments support the idea of a link between longevity and heredity, both in experimental animals and in the human species. In mice, genes in the major histocompatibility complex (MHC) are associated with a significant effect on life span. Results of analogous studies in man are confusing and contradictory. We have therefore investigated the question of an association of the human leucocyte antigen (HLA) and longevity in a large and ethnically homogeneous population. Our study population consisted of all 964 available inhabitants aged 85 years and over in the Dutch community of Leiden (pop. 104,000). Our control group comprised 2444 young inhabitants, aged 20-35 years, with an identical ethnic and demographic background. In addition, control groups of different age-brackets from the same region were used. Two antigens differed in frequency: HLA-B40 was lower and HLA-DR5 was higher in the group of 85 years and over, as compared to the control group, aged 20-35 years. Both differences were more evident in females. No major disease associations with HLA-B40 or HLA-DR5 have been reported. It is unlikely that these results are a chance observation: the overall similarity of the HLA pattern of the old and young age groups is a confirmation of their identical ethnic and demographic background and the changes as observed in the different age-groups were gradual. The biological meaning of these results is still unclear.

Lack of association between HLA and age in an aging population

In a sample of 228 Framingham Study participants aged 58 to 86 who were typed for HLA, neither frequencies of individual antigens nor heterozygosity at the A or B loci appeared to be related to age. Previously found associations could be chance occurrences, or HLA-related effects on longevity in the general population might be small. It is also possible that such effects occur at younger ages than those included in our study or that HLA is related to the aging process in a way that is detectable only at very advanced ages.

Autoantibodies and immunoglobulin allotypes in healthy North American Blacks of different age groups

A population of 291 healthy North American Black subjects of different ages was studied for immunoglobulin (Ig) allotypes and the prevalence of autoantibodies, to determine possible associations between Ig allotypes and age, autoantibodies and age, and Ig allotypes and autoantibodies. Indirect immunofluorescence was used to detect anti-gastric parietal cell, anti-smooth muscle, anti-thyroid microsomal, anti-nuclear, and anti-mitochondrial antibodies. The sera were typed for the Ig allotypes Gm(1, 2, 3, 5, 6, 13, 14, 17, and 21) and Km(1) with a hemagglutination-inhibition assay. A significant association between advanced age and an increased prevalence of anti-nuclear antibodies was observed in females. There was no significant association between Ig allotypes and the autoantibodies tested. The results suggest that Ig allotypes are not involved in the development of autoantibodies in healthy Blacks.