Pairs Of Unrelated Individuals Research Articles

A study of forensic genetics: ITO index distribution and kinship judgment between two individuals.

According to Mendel's law of genetic separation, there must be a certain blood relationship between members of the same family, and two individuals with blood relations must have the following three situations, that is, there are two homologous genes (I denotes), one homologous gene (T denotes), and no homologous genes (O denotes), which is the ITO index for calculating the blood relationship between two individuals. The AGGU Expressmarker 22 kit, ABI 3500 genetic analyzer, and GeneMapper ID-X v1.5 software were used to statistically analyze the ITO index of the gene locus of 5 kinds of samples, 28 pairs of monozygotic twins (MT), 4,000 pairs of parent-offspring (PO), 392 pairs of full sibling (FS), 138 pairs of half-siblings (HS) (including grandchildren, uncles, and nephews) and 3,500 pairs of unrelated individuals (UI). Observing the median distribution of ITO index found that from MT, PO, FS, HS to UI, the more distant the kinship, the smaller the ITO index. Full sibling index (FSI)/half-sibling index (HSI) ≥ 1 can be used as the FS discriminant standard, FSI/HSI < 1 can be used as the HS discriminant standard. According to the distance of kinship, from the direction of MT, PO, FS, HS, and UI, the proportion of the maximum ITO index of the same type of sample in the true kinship index item showed a decreasing trend. ITO index is an important statistical means to identify the kinship between two individuals, according to which the ITO index can accurately determine the kinship between individuals, which has high application value. MT index is not 0 to identify relatives as MT, PO index is an important indicator to distinguish between relatives as PO and FS. The critical values of ITO index discriminant values for UI and HS need to be further studied.

Concordance of a High Lipoprotein(a) Concentration Among Relatives

Lipoprotein(a) (Lp[a]) concentrations are a highly heritable and potential causal risk factor for atherosclerotic cardiovascular disease (ASCVD). Recent consensus statements by the European Atherosclerosis Society and American Heart Association recommend screening of relatives of individuals with high Lp(a) concentrations, but the expected yield of this approach has not been quantified in large populations. To measure the prevalence of high Lp(a) concentrations among first- and second-degree relatives of individuals with high Lp(a) concentrations compared with unrelated participants. In this cross-sectional analysis, pairs of first-degree (n = 19 899) and second-degree (n = 9715) relatives with measured Lp(a) levels from the UK Biobank study and random pairs of unrelated individuals (n = 184 764) were compared. Data for this study were collected from March 2006 to August 2010 and analyzed from December 2021 to August 2023. Serum Lp(a) levels, with a high Lp(a) level defined as at least 125 nmol/L. Concordance of clinically relevant high Lp(a) levels in first- and second-degree relatives of index participants with high Lp(a) levels. A total of 52 418 participants were included in the analysis (mean [SD] age, 57.3 [8.0] years; 29 825 [56.9%] women). Levels of Lp(a) were correlated among pairs of first-degree (Spearman ρ = 0.45; P < .001) and second-degree (Spearman ρ = 0.22; P < .001) relatives. A total of 1607 of 3420 (47.0% [95% CI, 45.3%-48.7%]) first-degree and 514 of 1614 (31.8% [95% CI, 29.6%-34.2%]) second-degree relatives of index participants with high Lp(a) levels also had elevated concentrations compared with 4974 of 30 258 (16.4% [95% CI, 16.0%-16.9%]) pairs of unrelated individuals. The concordance in high Lp(a) levels was generally consistent among subgroups (eg, those with prior ASCVD, postmenopausal women, and statin users). The odds ratios for relatives to have high Lp(a) levels if their index relative had a high Lp(a) level compared with those whose index relatives did not have high Lp(a) levels were 7.4 (95% CI, 6.8-8.1) for first-degree relatives and 3.0 (95% CI, 2.7-3.4) for second-degree relatives. The findings of this cross-sectional study suggest that the yield of cascade screening of first-degree relatives of individuals with high Lp(a) levels is over 40%. These findings support recent recommendations to use this approach to identify additional individuals at ASCVD risk based on Lp(a) concentrations.

An empirical evaluation of the estimation of inbreeding depression from molecular markers under suboptimal conditions.

Inbreeding depression (ID), the reduction in fitness due to inbreeding, is typically measured by the regression of the phenotypic values of individuals for a particular trait on their corresponding inbreeding coefficients (F). While genealogical records can provide these coefficients, they may be unavailable or incomplete, making molecular markers a useful alternative. The power to detect ID and its accuracy depend on the variation of F values of individuals, the sample sizes available, and the accuracy in the estimation of individual fitness traits and F values. In this study, we used Drosophila melanogaster to evaluate the effectiveness of molecular markers in estimating ID under suboptimal conditions. We generated two sets of 100 pairs of unrelated individuals from a large panmictic population and mated them for two generations to produce non-inbred and unrelated individuals (F = 0) and inbred individuals (full-sib progeny; F = 0.25). Using these expected genealogical F values, we calculated inbreeding depression for two fitness-related traits, pupae productivity and competitive fitness. We then sequenced the males from 17 non-inbred pairs and 17 inbred pairs to obtain their genomic inbreeding coefficients and estimate ID for the two traits. The scenario assumed was rather restrictive in terms of estimation of ID because: (1) the individuals belonged to the same generation of a large panmictic population, leading to low variation in individual F coefficients; (2) the sample sizes were small; and (3) the traits measured depended on both males and females while only males were sequenced. Despite the challenging conditions of our study, we found that molecular markers provided estimates of ID that were comparable to those obtained from simple pedigree estimations with larger sample sizes. The results therefore suggest that genomic measures of inbreeding are useful to provide estimates of inbreeding depression even under very challenging scenarios.

Efficiency Analysis of Uncle-Nephew Relationship Identification by Increasing STR Markers and Adding Reference Samples.

To estimate the system efficiency of uncle-nephew relationship identification by increasing STR markers and adding reference samples based on the test results of simulated data and real samples, so as to provide references for selecting the appropriate number of STRs and reference samples for uncle-nephew relationship identification. Five common models of uncle-nephew relationship identification were constructed by adding different reference samples. In each model, the likelihood ratio (LR) for 10 000 pairs of uncle-nephew relationships and 10 000 pairs of unrelated individuals were simulated by detecting 19, 39 or 55 STRs, and the system efficiency at different thresholds was simulated. The samples of the Han population in Zhejiang were collected, and 55 autosomal STRs were obtained by using SiFaSTRTM 23plex kit, Goldeneye® DNA ID 22NC kit and AGCU 21+1 PCR amplification kit. When 19, 39 and 55 STRs were detected, the LR of each model and system efficiency under different thresholds were calculated and compared with the simulation results. Under the same detection system, the calculated results of simulated data and corresponding true samples were basically consistent. In the same model, there was a positive correlation between the system efficiency of uncle-nephew relationship identification and the number of STRs detected. Moreover, the system efficiency of introducing relatives was higher than identifying only two individuals. The order of preference for the introduction of relatives was the full sibling (or mother) of the uncle and the full sibling (or mother) of the nephew. The system efficiency of uncle-nephew relationship identification could be improved by increasing the number of STRs and introducing known relatives, which would provide the basis for selecting the most appropriate detection system and reference individuals in actual cases.

Pairwise kinship analysis of 17 pedigrees using massively parallel sequencing

With the tremendous development of massively parallel sequencing (MPS) in the last decade, it has been widely applied in basic science, clinical diagnostics, microbial genomics, as well as forensic genetics. MPS has lots of advantages that may facilitate the kinship analysis. In this study, 243 Chinese Han individuals from 17 families were involved and sequenced using the ForenSeq™ DNA Signature Prep Kit (Verogen, Inc., San Diego, USA), which provided the sequence information of 27 autosomal STRs (A-STRs), 7 X chromosomal STRs (X-STRs), 24 Y chromosomal STRs (Y-STRs) and 94 identity-informative SNPs (iSNPs). A total of 275 pairs of parent-child, 123 pairs of full siblings, 1 pair of twins, 1 pair of half siblings, 158 pairs of grandparent-grandchild, 222 pairs of uncle/aunt-nephew/niece and 121 pairs of first cousins, as well as 701 pairs of unrelated individuals were identified. Using both likelihood ratio (LR) and identical by state (IBS) methods, the kinship analysis was conducted among these relative and non-relative pairs based on the A-STRs and SNPs. As a result, the ForenSeq Signature Kit could solve the analysis of parent-child (t1 = −4, t2 = 4), full siblings (t1 = −2, t2 = 2) and most second-degree kinships (t1 = −1, t2 = 1) using the LR method. When the IBS method was applied, 123 full sibling pairs had a higher average IBS value than other kinship groups in this study. And the IBS method could play a role in the testing of parent-child and full siblings.

Haplotype Sharing Provides Insights into Fine-Scale Population History and Disease in Finland

Finland provides unique opportunities to investigate population and medical genomics because of its adoption of unified national electronic health records, detailed historical and birth records, and serial population bottlenecks. We assembled a comprehensive view of recent population history (≤100 generations), the timespan during which most rare-disease-causing alleles arose, by comparing pairwise haplotype sharing from 43,254 Finns to that of 16,060 Swedes, Estonians, Russians, and Hungarians from geographically andlinguistically adjacent countries with different population histories. We find much more extensive sharing in Finns, with at least one ≥ 5 cM tract on average between pairs of unrelated individuals. By coupling haplotype sharing with fine-scale birth records from more than 25,000 individuals, we find that although haplotype sharing broadly decays with geographical distance, there are pockets of excess haplotype sharing; individuals from northeast Finland typically share several-fold more of their genome in identity-by-descent segments than individuals from southwest regions. We estimate recent effective population-size changes through time across regions of Finland, and we find that there was more continuous gene flow as Finns migrated from southwest to northeast between the early- and late-settlement regions than was dichotomously described previously. Lastly, we show that haplotype sharing is locally enriched by an order of magnitude among pairs of individuals sharing rare alleles and especially among pairs sharing rare disease-causing variants. Our work provides a general framework for using haplotype sharing to reconstruct an integrative view of recent population history and gain insight into the evolutionary origins of rare variants contributing to disease.

Sensitivity of Dental Phenotypic Data for the Identification of Biological Relatives

AbstractUsing modern samples of known kin, this paper evaluates two fundamental aspects of kinship analysis in archaeological contexts: (1) choice of data (dental metrics or morphology) and (2) analytical approach (multivariate, distance‐based approach or a ‘rare trait’ analysis). Stone dental casts were analysed from 155 female individuals from four sampling locations in Kenya. Of these 155 individuals, only three pairs were close kin: mother–daughter, sister–sister, and first‐cousin–first‐cousin dyads. After variable winnowing, inter‐individual distances or similarities were calculated using 11 odontometric variables and 25 dental morphological variables. Resulting distance matrices were ordinated in two dimensions using multidimensional scaling. Odontometric data performed relatively well at identifying known relative pairs, but the results were heavily affected by choice of similarity measure (e.g. Euclidean distances vs. Gower coefficients) and pre‐analysis data treatments (e.g. raw data vs. principal components). Dental morphological data performed comparably with odontometric data but were slightly less effective. Rare traits were identified and compared among relative pairs for concordance, with mixed results. Rare morphological features were randomly distributed throughout the population and were not exclusively found in close kin. In combination, results indicated the sister–sister dyad was most consistently identified; however, in no analysis were relatives more phenotypically similar than all random pairs of unrelated individuals. A multivariate, distance‐based approach was more effective than rare traits at identifying relative pairs, but even under ideal circumstances, there is not enough variation present in the dentition to faithfully identify close relatives in the absence of contextual archaeological data. Copyright © 2017 John Wiley &amp; Sons, Ltd.

Full Sibling Identification by IBS Scoring Method and Establishment of the Query Table of Its Critical Value

To establish a query table of IBS critical value and identification power for the detection systems with different numbers of STR loci under different false judgment standards. Samples of 267 pairs of full siblings and 360 pairs of unrelated individuals were collected and 19 autosomal STR loci were genotyped by Goldeneye™ 20A system. The full siblings were determined using IBS scoring method according to the 'Regulation for biological full sibling testing'. The critical values and identification power for the detection systems with different numbers of STR loci under different false judgment standards were calculated by theoretical methods. According to the formal IBS scoring criteria, the identification power of full siblings and unrelated individuals was 0.764 0 and the rate of false judgment was 0. The results of theoretical calculation were consistent with that of sample observation. The query table of IBS critical value for identification of full sibling detection systems with different numbers of STR loci was successfully established. The IBS scoring method defined by the regulation has high detection efficiency and low false judgment rate, which provides a relatively conservative result. The query table of IBS critical value for identification of full sibling detection systems with different numbers of STR loci provides an important reference data for the result judgment of full sibling testing and owns a considerable practical value.

Study of autosomal STR loci with IBS method in full sibling identification.

We investigated the application of 51 autosomal short tandem repeat (STR) loci with the identity by state (IBS) method and a discriminant function algorithm in full-sib identification. A total of 342 pairs of full sibs (FSs) and 3900 pairs of unrelated individuals (UIs) were genotyped for 51 STR loci. Groups were formed in accordance with discrimination power (DP) values and the number of loci, and IBS scores of FSs and UIs were analyzed and compared. The discriminant functions of FS-UI were determined by using the Fisher discriminant with SPSS software. All IBS in FSs and UIs groups showed normal distributions and there were significant differences between FS-UI. Receiver operating characteristic curves revealed that the detection efficiency of full-sib identification was affected by both the locus polymorphism and the number of loci detected. Comparing the rate of false positive and false negative of discriminant function between groups, a higher average DP value and larger number of loci detected were associated with a lower rate of miscarriage of justice and were more helpful for full-sib identification. STRs with higher DP values should be selected when additional autosomal markers are required for FS identification. Discriminant analysis with the IBS method is highly applicable for the FS-UI test.

Effect of genome and environment on metabolic and inflammatory profiles.

Twin and family studies have established the contribution of genetic factors to variation in metabolic, hematologic and immunological parameters. The majority of these studies analyzed single or combined traits into pre-defined syndromes. In the present study, we explore an alternative multivariate approach in which a broad range of metabolic, hematologic, and immunological traits are analyzed simultaneously to determine the resemblance of monozygotic (MZ) twin pairs, twin-spouse pairs and unrelated, non-cohabiting individuals. A total of 517 participants from the Netherlands Twin Register, including 210 MZ twin pairs and 64 twin-spouse pairs, took part in the study. Data were collected on body composition, blood pressure, heart rate, and multiple biomarkers assessed in fasting blood samples, including lipid levels, glucose, insulin, liver enzymes, hematological measurements and cytokine levels. For all 51 measured traits, pair-wise Pearson correlations, correcting for family relatedness, were calculated across all the individuals in the cohort. Hierarchical clustering techniques were applied to group the measured traits into sub-clusters based on similarity. Sub-clusters were observed among metabolic traits and among inflammatory markers. We defined a phenotypic profile as the collection of all the traits measured for a given individual. Average within-pair similarity of phenotypic profiles was determined for the groups of MZ twin pairs, spouse pairs and pairs of unrelated individuals. The average similarity across the full phenotypic profile was higher for MZ twin pairs than for spouse pairs, and lowest for pairs of unrelated individuals. Cohabiting MZ twins were more similar in their phenotypic profile compared to MZ twins who no longer lived together. The correspondence in the phenotypic profile is therefore determined to a large degree by familial, mostly genetic, factors, while household factors contribute to a lesser degree to profile similarity.

Comparison study in determination of full sibling with Identifiler multiplex system between ITO method and identity by state scoring method

In this study, 2003 pairs of unrelated individuals (UI group) and 280 pairs of full siblings (FS group) were genotyped with Identifiler system. Cumulative full sibling index (CFSI) and the identity by state (IBS) score of Identifiler system (IBSi) between each pair of individuals were calculated with ITO method and direct counting method, respectively. Difference of Log 10CFSI or IBSi between the two groups was statistically significant ( P < 0.0001). Consequently, two groups of discrimination functions were established with Fisher discriminant analysis based on Log 10CFSI and IBSi, respectively. Total false determination rate of the two groups of functions were 3.48% with ITO and 2.98% with IBS method, respectively. High consistency of the two different method was indicated with Kappa index = 0.8841 ( P < 0.0001). Results suggested power of IBS method was similar to that of ITO method in FS determination, with advantages of convenience in calculation and independence on the allele frequency of STR loci.

Studying Gene and Gene-Environment Effects of Uncommon and Common Variants on Continuous Traits: A Marker-Set Approach Using Gene-Trait Similarity Regression

Genomic association analyses of complex traits demand statistical tools that are capable of detecting small effects of common and rare variants and modeling complex interaction effects and yet are computationally feasible. In this work, we introduce a similarity-based regression method for assessing the main genetic and interaction effects of a group of markers on quantitative traits. The method uses genetic similarity to aggregate information from multiple polymorphic sites and integrates adaptive weights that depend on allele frequencies to accomodate common and uncommon variants. Collapsing information at the similarity level instead of the genotype level avoids canceling signals that have the opposite etiological effects and is applicable to any class of genetic variants without the need fordichotomizing the allele types. To assess gene-trait associations, we regress trait similarities for pairs of unrelated individuals on theirgenetic similarities and assess association by using a score test whose limiting distribution is derived in this work. The proposed regression framework allows for covariates, has the capacity to model both main and interaction effects, can be applied to a mixture of different polymorphism types, and is computationally efficient. These features make it an ideal tool for evaluating associations between phenotype and marker sets defined by linkage disequilibrium (LD) blocks, genes, or pathways in whole-genome analysis.

Matching and Partially-Matching DNA Profiles

The DNA profiles of two individuals can have 0, 1, or 2 pairs of alleles that are the same at each locus. These events may be called mismatches, partial matches or matches, respectively, and they have probabilities that depend on the population proportions of alleles as well as the population structure parameter theta. The observed and expected numbers of pairs of individuals with various numbers of matching or partially matching loci in FBI and Australian databases are found to be in good agreement provided theta is set equal to some small value greater than zero. The likelihood ratios for two individuals having a specified degree of relationship versus being unrelated also depend on the numbers of matching and partially matching loci, but even unrelated pairs of individuals can have likelihood ratios that support hypotheses of relatedness. Matching probabilities allow predictions to be made for the sizes of databases that are expected to contain a pair of individuals with high numbers of matching loci. It is very likely that two individuals with at least 9 matching loci among the 13 CODIS loci have already been typed.

Natural skip oviposition of the mosquito Aedes aegypti indicated by codominant genetic markers.

This study examines the use of codominant restriction fragment length polymorphism (RFLP) markers to estimate the number of sibling families found within and among oviposition sites used by the mosquito Aedes aegypti (L) (Diptera: Culicidae). Estimates were made using pairwise relatedness (rxy) calculations based on alleles shared between individuals. Genotypes for eight laboratory mosquito families were determined at six RFLP loci and the observed allele frequencies were used to generate simulated distributions of rxy from full-sibling and unrelated pairs of individuals. The midpoint (mp) between the means of the pairwise rxy distributions was used to discriminate full-sibling families from unrelated families. Clusters of individuals with rxy values higher than the mp value were grouped as putative sibling families. This method was tested by calculating actual rxy for all pairwise comparisons of the known laboratory full-sibling and paternal half-sibling families, followed by upgma cluster analysis to group sibling families. The technique was then used for sibling estimations on wild caught mosquitoes collected at three locations in Trinidad, West Indies. From field populations, 35 families were estimated among 122 individuals tested with an average of 6.2 families per container. Members of 19 predicted families clustered as groups across multiple containers, providing molecular evidence for skip-oviposition behaviour in Ae. aegypti females, whereby individual females oviposit in more than one container.

Allele sharing in first-degree and unrelated pairs of individuals in the Ge.F.I. AmpFlSTR® Profiler Plus™ database

Eleven Italian forensic laboratories participated in a population study based on the AB Profiler Plus™ loci with proficiency testing. The validated database, including 1340 individuals, is available on-line. Tests for Hardy–Weinberg equilibrium, gametic unbalance, and heterogeneity of gene frequency were generally not significant. Gene frequencies at each locus were consistent with those of two previously published Italian studies, but different from a third. Individuals of each subsample were paired, and the total number of alleles shared across the nine loci was determined in each pair. The analysis was replicated over the total sample. In addition, two samples of mother–child pairs (N=315) and full-sib pairs (N=91) were subjected to allele sharing analysis. The resulting distributions were sufficiently distinct from the sample of unrelated pairs as to be of practical usefulness.

4 Familial resemblance and heritability

Familial resemblance, which arises when members within families are more similar than are unrelated pairs of individuals, may be estimated in terms of correlations (or covariances) among family members. The magnitudes of such correlations generally reflect both the extent of environmental sharing and the degree of biological relationship between the relatives. Heritability, or more appropriately multifactorial heritability or generalized heritability, quantifies the strength of the familial resemblance and represents the percentage of variance ina trait that is due to all additive familial effects including additive genetic effects and those of the familial environment. However, the traditional concept of heritability, which may be more appropriately called the genetic heritability, represents only the percentage of phenotypic variance due to additive genetic effects. Resolving the sources of familial resemblance entails other issues. For example, there may be major gene effects that may be largely or entirely nonadditive, temporal or developmental trends, and gene-gene (epistasis) and gene-environment interactions. The design of a family study determines which of these sources are resolvable. For example, in intact nuclear families consisting of parents and offspring, the genetic and familial environmental effects are not resolvable because these relatives share both genes and environments. However, extended pedigrees and twin and adoption study designs allow separation of the heritable effects and, possibly, more complex etiologies, including interactions. Various factors affect the estimation and interpretability of heritability, for example, assumptions regarding linearity and additivity of the effects, assortative mating, and the underlying distribution of the data. Nonnormality of the data can lead to errors in hypothesis testing, although it yields reasonably unbiased estimates. Fortunately, these and other complications can be directly modeled in many of the sophisticated software packages available today in genetic epidemiology.

Causes and consequences of incest avoidance in the cooperatively breeding mole-rat, Cryptomys darlingi (Bathyergidae)

A number of social mole-rat species maintain a strong reproductive skew (only one breeding pair in the group) solely through incest avoidance. Incest avoidance probably evolved for one of two reasons, namely for actually maintaining a reproductive skew or, alternatively, to avoid high inbreeding depression. In the latter case a strong reproductive skew would result as a fortuitous by-product of the combination of a cloistral family life style of mole-rats and incest avoidance. We undertook breeding experiments in which the fertility of pairs of unrelated individuals were compared with that of pairs of double first cousins. Inbreeding depression was remarkably high and an accompanying model suggests that it may be sufficient to support the idea that strong incest avoidance evolved primarily to eliminate the costs of inbreeding and subsequently facilitated the evolution of reproductive skew.

Genealogy reconstruction from short tandem repeat genotypes in an Amazonian population.

We have reconstructed partial genealogies in a sample of 44 SW Amazonian Rondonian Surui, in which 45 dinucleotide short tandem repeat polymorphisms had previously been typed. The genotypes of 488 pairs of individuals having an age difference of 13 or greater were compared, and parentage was excluded if a pair failed to share an allele at more than one locus. In order to test the power of this method, we computed the expected distribution of the number of exclusionary loci for such pairs of unrelated individuals, as well as that for individuals with different degrees of relatedness, and compared it to the observed distribution. We estimated that the pairs compared contained approximately 20% of individual pairs with a first-cousin relation or closer. A total of 25 pairs were identified as possible parent-child. In three instances, we could identify two or more children having a common parent; we computed a relatedness coefficient in order to establish whether the children were full or half sibs. The genealogies inferred show that instances of polygyny and polyandry (or, alternatively, serial mating), in addition to apparent monogamy, can be found among the Surui. The Surui sample can be used as a model for paleoanthropological populations, in which the determination of relatedness can provide further insights into the social structure of past populations. We estimate that, depending on the history of the populations and the degree of inbreeding, 10-20 highly informative nuclear loci should be typed in order to infer genealogies with acceptable confidence.

Use of microsatellite loci to classify individuals by relatedness.

This study investigates the use of microsatellite loci for estimating relatedness between individuals in wild, outbred, vertebrate populations. We measured allele frequencies at 20 unlinked, dinucleotide-repeat microsatellite loci in a population of wild mice (Mus musculus), and used these observed frequencies to generate the expected distributions of pairwise relatedness among full sib, half sib, and unrelated pairs of individuals, as would be estimated from the microsatellite data. In this population one should be able to discriminate between unrelated and full-sib dyads with at least 97% accuracy, and to discriminate half-sib pairs from unrelated pairs or from full-sib pairs with better than 80% accuracy. If one uses the criterion that parent-offspring pairs must share at least one allele per locus, then only 15% of full-sib pairs, 2% of half-sib pairs, and 0% of unrelated pairs in this population would qualify as potential parent-offspring pairs. We verified that the simulation results (which assume a random mating population in Hardy-Weinberg and linkage equilibrium) accurately predict results one would obtain from this population in real life by scoring laboratory-bred full- and half-sib families whose parents were wild-caught mice from the study population. We also investigated the effects of using different numbers of loci, or loci of different average heterozygosities (He), on misclassification frequencies. Both variables have strong effects on misclassification rate. For example, it requires almost twice as many loci of He = 0.62 to achieve the same accuracy as a given number of loci He = 0.75. Finally, we tested the ability of UPGMA clustering to identify family groups in our population. Clustering of allele matching scores among the offspring of four sets of independent maternal half sibships (four females, each mated to two different males) perfectly recovered the true family relationships.

Estimates of cytotoxic T-lymphocyte precursor frequencies against HLA class I antigens in responder-stimulator pairs with a negative mixed lymphocyte culture reaction

Functional studies of helper and cytotoxic T cells in families with recombinant HLA haplotypes have played a crucial role in the early studies of the HLA chromosomal region. It has been shown that for the generation of CTLs directed against HLA-A or -B antigen differences an additional difference in the HLA-D region between responder and stimulator cells was a prerequisite. We have re-examined in a sensitive limiting dilution assay the possibility of generating CTL against HLA class I antigens in responder—stimulator pairs with a negative MLC reaction of two recombinant families (differing in one or two HLA class I antigens but identical in class II antigens) and two pairs of unrelated individuals. In all cases we could detect low but definitely measurable CTL activity (8–15 CTL precursors in 10 6 PEMCs) directed against the mismatched class I HLA antigen(s). We conclude that mismatches in class I HLA antigens in MLC nonreactive responder—stimulator pairs can induce generation of allospecific CTLs. This has implications in allogeneic bone marrow transplantation with HLA-matched unrelated donors; i.e., in the case of an HLA-A,B,DR matched donor a low donor CTLpf against the recipient may be an indication of a serologically not-detected class I HLA “subtype” incompatibility which might cause graft-versus-host disease.