Association between major histocompatibility antigen and reproductive performance

Novel alleles of HLA-DQ and -DR loci show association with recurrent miscarriages among South Indian women

BACKGROUND In this study, recurrent miscarriages (RMs) are defined as loss of two or more clinically detectable pregnancies before 20 weeks of gestation. HLA has been thought to play a role in RM. However, the results of earlier studies on the role of different human leucocyte antigen (HLA) genes were conflicting and inconclusive. In the present study, we investigate HLA genes (HLA-DRA, HLA-DRB1, HLA-DQA1 and HLA-DQB1) in RM couples with unknown etiology and normal couples. METHODS Blood samples from 143 RM couples and 150 control couples were analyzed, firstly to validate previously reported association studies and secondly to explore whether any novel alleles or haplotypes specific to Indian populations can be observed to be associated with RM. HLA typing was carried out by DNA sequencing. RESULTS Results suggest an association of the DQB1*03:03:02 allele with RM (odd ratio = 2.66; p(c) = 0.02; confidence interval = 1.47-4.84). Haplotypes of the DQA1 and DQB1 risk alleles also showed a significant association with RM, albeit not after Bonferroni correction for multiple comparisons. CONCLUSIONS HLA-DQB1 appears to have a strong involvement in the manifestation of RM in this population from South India. The current genetic analysis of RM and control couples not only highlights the genes exhibiting a strong etiological role but also reflects the protective nature of some HLA genes against RM. Nevertheless, most of these alleles/haplotypes were not those that are implicated in RM in other ethnic backgrounds, and hence require further validation in other populations of India, from different ethnic and/or geographic backgrounds.

Pregnancy immunology

Immunology is a fast developing and intriguing biomedical science, which can give rise to specific considerations about the physiological process of both successful and unsuccessful vivparous pregnancy. It is normal in clinical organ transplantation for unmatched foreign tissues (allografts) to provoke immunological rejection by the host, unless there has been prior tissue matching (histocompatibility antigen tissue typing) or immunosuppressive therapy. Thus, it is still not fully clear how, after ‘random’ mating, haplo-nonidentical fetal tissue is able to survive in the potentially hostile immunocompetent maternal environment. The majority of pregnancies survive uninterrupted and there has now been much speculation and research regarding the immunological success of pregnancy (i.e. nature’s transplant). Medawar orginally offered four nonexclusive hypotheses to explain the enigmatic immunological survival of normal pregnancy:

1) the conceptus is not immunogenic and therefore does not evoke an immunological response;

2) pregnancy alters the maternal immune response;

3) the uterus is an immunologically privileged site;

4) the placenta is an immunological barrier between the mother and the as yet immunologically incompetent fetus.

Before discussing these, as well as some of the clinical immunological problems that may arise during pregnancy, it is necessary to outline some of the basic components of the normal immune system. This will lead to a description of current understanding of immunological events at the fetomaternal interface as well as the maternal immune response in human pregnancy.

14th International HLA and Immunogenetics Workshop: Report from the reproductive immunology component

The aim of the study was to investigate whether human leukocyte antigen (HLA) allele sharing between partners or the maternal killer immunoglobulin-like receptor (KIR) repertoire is associated with recurrent spontaneous abortion (RSA) and repeated implantation failure after in vitro fertilization (IVF)/embryo transfer. From a total population of 158 RSA couples, 40 couples with repeated implantation failures (IVF) and 81 control couples, reported by five different laboratories, analysis was performed for (a) HLA sharing in 50 RSA, 31 IVF and 31 control couples, (b) DQA1*0505 sharing/homozygosity among partners in 108 RSA, 40 IVF and 36 control couples, and (c) the women's KIR repertoire in 46 RSA, 26 IVF and 36 control wives. RSA couples were divided into alloimmune aborter (RSAallo) and autoimmune aborter (RSAauto). The results oppose to the suggestion that increased HLA sharing per se or a limited maternal KIR repertoire predisposes to RSA or IVF failure. However, the observation of a slightly higher percentage of DQA1*0505 sharing in the RSAauto and the IVF group needs further investigation. The ratio of inhibitory to activating KIR (actKIR) was slightly lower in RSAallo and IVF women (1.9 vs 2.6 in controls), while in a high percentage of these women, the standard receptors of the KIR A haplotype were combined with actKIR/s of the haplotype B (66.6% and 45.4% vs 20% and 15.3% in RSAauto and control groups). This may suggest a possible involvement of actKIRs in embryo implantation and the maintenance of pregnancy and also requires further investigation.

Linkage disequilibrium between human leukocyte antigen (HLA) class II and HLA-G--possible implications for human reproduction and autoimmune disease

A line of investigation indicates that one or several genes in the human major histocompatibility complex (MHC) influences reproductive success. Studies have revealed associations between human leukocyte antigen (HLA) class II genes and risk of recurrent spontaneous abortion (RSA) and pre-eclampsia. However, these genes are not expressed at the feto-maternal interface. Furthermore, associations between polymorphisms in the nonclassical HLA class Ib gene, HLA-G, and reproductive outcome have been demonstrated. HLA-G is expressed by extravillous trophoblast during pregnancy, making it a more obvious candidate gene for a possible influence on pregnancy outcome. HLA-G has immunomodulatory functions. We have studied linkage disequilibrium between HLA class II genes, primarily HLA-DRB1 alleles, and HLA-G alleles in women with RSA and their partners (n = 103) and in control women and their partners (n = 92). We found a significant linkage disequilibrium between HLA-DR3 and HLA-G*010102 in both the RSA and control populations. For all four studied HLA loci, the alleles in the haplotype HLA-DRB1*03.DQA1*05.DQB1*02.G*010102 was in clear linkage disequilibrium. This HLA haplotype has repeatedly been associated with different autoimmune diseases but also with RSA. The G*010102 allele includes a 14-bp sequence polymorphism in the 3' untranslated region of the gene, which has been associated with differences in HLA-G mRNA alternative splicing and stability. This 14-bp polymorphism has also been associated with RSA, pre-eclampsia, and outcome of in vitro fertilization. Implications of HLA polymorphism--and other polymorphic genes in the MHC for pregnancy outcome--and for autoimmune diseases during pregnancy are discussed.

Association of human leucocyte antigen sharing with recurrent spontaneous abortions

An estimated 15% of clinically recognized pregnancies abort spontaneously. Recurrent spontaneous abortion (RSA) is defined as three or more consecutive miscarriages conceived with the same partner in the absence of uterine, genetic or autoimmune abnormalities. Evidence points to human leucocyte antigens (HLA) as playing a role in the successful development of the foetus. In particular, HLA compatibility is more prevalent in couples experiencing reproductive failure, especially RSA couples, compared to fertile couples. According to the immunological hypothesis, an adequate immune response is necessary for proper implantation of the embryo; conversely, a depressed response of maternal lymphocytes to the stimulation by paternal antigens because of HLA sharing can result in disorders, such as RSA. The genetic hypothesis implicates homozygosity for recessive lethal alleles in linkage disequilibrium with specific HLA haplotypes. The specificity of HLA alleles or haplotypes responsible for or linked to other RSA susceptibility genes remains unclear. In this study, we identified 40 observational studies (32 case-control, five cohort, one cross-sectional, one case series and one basic science) that examined the associations between HLA and RSA, focusing on HLA allele couple and maternal-foetal sharing, and the special role of HLA-G. We sought to identify consistent findings among studies examining similar questions. Evidence remains divided concerning the role of HLA allele couple sharing. Of major concern is the focus of many studies on couple sharing as a proxy measure of maternal-foetal sharing. Therefore, adequately powered studies are needed, which employ standard case definitions and reproducible methodologies to directly assess the role of maternal-foetal HLA sharing on the risk of RSA.

HLA-C and -Bw typing of couples with unexplained recurrent miscarriages

There is now evidence that the classical HLA class I molecule HLA-C is expressed on extravillous trophoblasts together with non-classical HLA-G molecules. Since clones of NK-cells are inhibited differently by supertypic epitopes associated with HLA-C and -B alleles we found it of interest to study HLA-C and -Bw polymorphism in 35 couples with recurrent miscarriage and 30 control couples with normal fecundity. All HLA assignments were undertaken by DNA techniques. The distribution of HLA-C alleles or the HLA-C associated supertypic epitopes recognized by NK1 or NK2 clones was not significantly different between patients and controls. The distribution of couples according to the number of NK1 and NK2 epitopes in the couple was similar in patients and controls. With respect to the HLA-Bw epitopes recognized by NKB1 clones, in 46% of the couples with recurrent miscarriage none of the spouses carried the HLA-Bw4 epitope compared with only 17% of the control couples (P < 0.02). It is concluded that the HLA-Bw4 epitope is carried more frequently by couples with normal fecundity than couples with recurrent miscarriage. The fetuses of couples with recurrent miscarriage are thus expected to lack expression of HLA-Bw4 epitopes on the trophoblast more often than fetuses of normal couples which might be of importance for the inhibition of NK-cell mediated antitrophoblast cytotoxicity.

Increased frequency of HLA-DR4 allele in women with unexplained recurrent spontaneous abortions, detected by the method of PCR-SSP

We investigated whether HLA-DR genes are associated with the etiology of unexplained recurrent spontaneous abortion (URSA), by using the polymerase chain reaction-sequence-specific primers (PCR-SSP) method, which is more accurate than serological typing. In women (n = 27) who experienced three or more consecutive spontaneous abortions in the first trimester, the frequency of the DR4 allele was significantly increased (relative risk = 4.25, P = 0.020) when compared with controls (n = 22) who experienced two or more full-term deliveries and no miscarriage. After high-resolutional analysis by a second PCR-SSP in positive cases for the DR4 allele phenotypic frequencies of HLA-DRB1*04 sub-alleles were disclosed. The most frequent sub-allele was DRB1*0405, followed by DRB1*0406 in both women with URSA and controls. However, none of the specific sub-alleles were attributed statistically to the increase in the DR4 allele in women with URSA.

HLA sharing, anti-paternal cytotoxic antibodies and MLR blocking factors in women with recurrent spontaneous abortion

OBJECTIVE

To study the prevalence of HLA sharing between spouses and its correlation with presence of antipaternal cytotoxic antibody (APCA) and mixed lymphocyte reaction (MLR) blocking factors in recurrent spontaneous aborters (RSA).

DESIGN

Study was carried out at Sanjay Gandhi Postgraduate Institute of Medical Sciences (SGPGI), Lucknow, from 1988-1992. Hundred couples with 3 or more consecutive recurrent spontaneous abortions and equal number of age, parity and ethinically matched normal controls were selected for studying HLA, APCA and MLR blocking factors. Meta-analysis was performed using standard formula and significance was tested by Chi-square analysis.

RESULTS

Significant HLA sharing was observed in couples with RSA at A and DR loci compared to normal controls (p < 0.001). Twenty-seven point eight percent of couples with RSA were positive for APCA compared to 49% of controls (p < 0.01). MLR blocking factors were detected in 26% couples with RSA compared to 78% in controls (p < 0.001). An inverse correlation between HLA sharing and APCA and MLR positivity was demonstrated.

CONCLUSION

The study supports that greater HLA sharing between spouses, associated with lack of an appropriate immune response to them could be responsible for RSA.

Immunogenetic study of couples with recurrent spontaneous abortions

OBJECTIVES

Clinical observations suggest that genetic and immunologic disparity could be a factor in fecundity. The HLA system (HLA) is polymorphic and TLX (Trophoblast Lymphocyte Cross-Reactive), which is also polymorphic, seems to be linked to it. The immunologic hypothesis follows that excessive HLA and TLX-sharing could explain the rejection of a semi-allogenic blastocyst. Study objectives are therefore twofold; To determine whether or not there is significant HLA-sharing between spouses with unexplained recurrent spontaneous abortions (RSA) and to determine whether or not there is an association between some HLA specificities and RSA.

STUDY DESIGN

The study includes only Caucasian couples that have had three successive spontaneous abortions. These were distributed in two groups: Group E: 18 couples either with known aetiology or with secondary RSA; Group U: seven couples with unexplained primary RSA; Control group C: 21 couples with at least two children and no spontaneous abortions. Tissue typing for HLA-A and B molecules was performed using serotyping methodology based on lymphocytotoxicity reaction. The different DRB1 alleles (class II) were determined by oligotyping with a non-radioactive reverse dot-blot methodology.

RESULTS

Statistical comparison shows that the number of couples without shared specificity is not significantly different between the three groups for each locus independently and for the set of three. Our results show also that the allelic frequencies are not significantly different between the three groups.

CONCLUSIONS

There is no higher HLA-sharing in couples with RSA than in fertile couples. Similarly, no particular HLA specificity can be associated with the RSA.

Immunologically mediated abortion (IMA)

Roughly 20% of all clinical pregnancies evolve into "spontaneous abortions". The causes of spontaneous abortion have been determined in under 60% of the total and comprise genetic, infectious, hormonal and immunological factors. In some cases the immune tolerance mechanism may be impaired and the foetus immunologically rejected (IMA, immunologically mediated abortion). The immunological mechanism implicated depends on the time in which pregnancy loss takes place. During preimplantation and up to the end of implantation (13th day) the cell-mediated immune mechanism (potential alloimmune etiologies) is responsible for early abortion. This mechanism involves immunocompetent decidual cells (eGL, endometrial granulated lymphocytes) already present during pre-decidualization (late luteal phase) and their production of soluble factors or cytokines. Once the implantation process is over, after blastocyst penetration of the stroma and the decidual reaction of uterine tissue, IMA could be caused by cell-mediated and humoral mechanism (anti-paternal cytotoxic antibodies or autoantibody etiology), by the production of paternal anti major histocompatibility complex antibodies, or even by an autoimmune disorder leading to the production of autoantibodies (antiphospholipid antibodies, antinuclear antibodies or polyclonal B cell activation). The diagnostic work-up adopted to select IMA patients is crucial and includes primary (karyotype of both partners, toxo-test, hysterosalpingography, endometrial biopsy, thyroid function tests, serum hprolactin, luteal phase dating) and secondary (full hemochromocytometric test, search for LE cells, lupus anticoagulant, anticardiolipin, antinuclear antibodies, Rheumatoid factor, blood complement VDRL) investigations. Therapeutical approaches vary. If autoimmune disorders are demonstrated therapies with different combinations of corticosteroids, aspirin and heparin or intravenous immunoglobulin are administered. Otherwise, therapy with paternal or donor peripheral blood mononuclear cells should be instituted.

Nuclear fallout, low birthweight, and immune deficiency

An investigation of the mortality rates of young adults born in the postwar period of large-scale atmospheric nuclear testing (1945-1965) in the United States and other western industrial nations reveals an increasingly anomalous rise in mortality from its previous secular decline. Beginning in the late 1970s and particularly since 1983, the deterioration in the health of the 25-44 age group is related to in utero exposure to fission products in the milk and diet, associated with an unprecedented rise in underweight births and neonatal mortality known to be accompanied by loss of immune resistance. The 1945-1965 rise in the percentage of live births below 2500 grams is highly correlated with the amount of strontium-90 in human bone, both peaking in the mid-1960s. In the 1980s, for the baby boom generation (those born between 1945 and 1965), cancer incidence and mortality due to infectious diseases associated with a rising degree of immune deficiency, such as pneumonia, septicemia, and AIDS, increased sharply. This process of increasing immune deficiency appears to have been exacerbated by continuing secondary exposures to accidental reactor releases and by an acceleration of radiation-induced mutation of pathogenic microorganisms increasingly resistant to drugs.

Maternal-fetal HLA sharing and risk of newborn encephalopathy and seizures: a pilot study

A pilot case-control study was done to collect data on whether susceptibility to newborn encephalopathy and neonatal seizures is influenced by the degree of maternal-fetal sharing of HLA antigens. Cases included 13 infants with moderate or severe newborn encephalopathy and seven infants with neonatal seizures but no other signs of encephalopathy. Controls were neurologically normal infants matched to cases by date of birth, sex, race, and payment status. Infants and their mothers were typed for HLA-A, -B, -DR, and -DQ antigens. The observed frequency of sharing of maternal antigens was greater than expected (ie, 0.5) for cases compared to controls at the HLA-B, -DR, and -DQ loci but not for HLA-A. The risk of neurologic problems in the neonatal period was increased 6.3 times when there was more than one match at the HLA-DR or -DQ locus. Placental abnormalities were noted at delivery only among cases, and the mean placental weight in cases was 598 g versus 695 g in controls. Further studies with sample sizes sufficiently large to statistically test this hypothesis are needed.

Foeto-maternal compatibility in HLA-DR, -DQ, and -DP loci in Finnish couples suffering from recurrent spontaneous abortions

The polymorphism of Major Histocompatibility Complex (MHC) class II genes DRB, DQA, DQB, and DPA was studied by TaqI Restriction Fragment Length Polymorphism (RFLP) in recurrent spontaneous abortions (RSA). The study group consisted of 35 primary abortion (PA) couples (no children) and 15 secondary abortion (SA) couples (1-2 children before abortions). We found no increase in DR-DQ compatibility between the mother and the foetus in the Finnish RSA group. In contrast to findings in some other populations, foeto-maternal incompatibility was increased in the PA group. Thus, our results do not support the theory that increased MHC class II compatibility is a cause of abortions as such. The Finns are a small and relatively isolated population with a unique gene inheritance. Thus, one can speculate that, if the human MHC class II is in the linkage with disadvantageous 'fertility genes', and these genes might nonetheless still be clustered in only a few MHC haplotypes among the Finns. This would be the reason, that DR-DQ sharing is not seen. The presence of rare HLA alleles, such as DR2 and DR6, among the aborters also supports this. In addition, this study extends our previous findings on MHC class III in regards to PA and SA couples differing immunogenetically from each other. In MHC class II, this was most obvious in the DPA1 locus. The vast majority of SA women were heterozygous for the two most common DPA1 alleles (14.0 kb and 13.5 kb), resulting in significantly smaller chances for a DPA1 mismatched foetus to occur in the SA group than in the controls or in the PA women.

Concordance of parental race/ethnicity in relation to the risk of sudden infant death syndrome (SIDS)

It has been reported that parental human leukocyte antigen (HLA) compatibility is associated with certain adverse reproductive outcomes such as multiple spontaneous fetal losses and malformations, particularly among women without a prior livebirth. In order to study the relation between parental HLA compatibility and the risk of SIDS, a population-based case-control study was conducted using 1982-1990 Washington State linked birth and death certificate data. Concordance of parental race/ethnicity combined with prior maternal fetal loss was used as surrogate measures of parental HLA compatibility. The relation was evaluated separately among infants with and without a prior live-born sibling. Among first liveborn infants, those of racially discordant parents were at reduced risk of SIDS compared with those of racially concordant parents (relative risk [RR] = 0.57, 95% confidence interval = 0.34-0.96). Infants of white-minority parents were all at lower risk of SIDS than infants of white-white parents. Infants of racially concordant parents with two or more prior fetal losses were at increased risk of SIDS (RR = 2.44, 1.07-5.56), relative to infants of racially discordant parents. No such associations were observed among infants with prior live-born siblings. In fact, in this latter population, infants of racially concordant parents tended to have a lower risk of SIDS than those of discordant parents. This study suggests that a portion of SIDS cases, particularly among first live-born infants, may be due to parental HLA sharing. However, final determination of the existence of this relationship requires actual HLA typing of parents of both cases and controls.

A set of MHC haplotypes found among Finnish couples suffering from recurrent spontaneous abortions

PROBLEM AND METHOD

The role of major histocompatibility complex (MHC) genes in the etiology of recurrent spontaneous abortion (RSA) was studied by analyzing the polymorphism of several, at least 14, immunogenetically important MHC genes either by serological or molecular methods in 56 Finnish RSA couples, and in 29 infants born to these families during the follow-up period of two years after the abortions.

RESULTS

The haplotype analysis showed that the RSA couples had significantly increased sharing of MHC fragments, compared to the control families. Furthermore, the MHC risk markers for abortions defined 12 different, extended MHC haplotypes that were found in a significantly higher proportion among persons in the RSA group (45%) than in the controls (11%). However, neither of these observations associated with the reproductive success of the study couples.

CONCLUSIONS

The results suggest that extended MHC haplotypes, disadvantageous for reproduction, exist in some isolated populations, such as the Finns.

Immunologic tests in the evaluation of reproductive disorders: a critical review

OBJECTIVE

The purpose of this study was to evaluate the clinical usefulness of immunologic assays proposed to assist in the diagnosis of alloimmune causes of recurrent spontaneous abortion.

STUDY DESIGN

Human leukocyte antigen typing, maternal antipaternal lymphocytotoxic antibody testing, and mixed lymphocyte culture assays were performed on 609 couples with recurrent spontaneous abortion, 92 infertile couples, and 43 fertile couples. The frequency of HLA antigen sharing and the presence of lymphocytotoxic antibodies and mixed lymphocyte culture inhibitors was compared among the populations.

RESULTS

Sharing of two or more HLA-A, HLA-B, HLA-C, or HLA-DR antigens was observed in 41% (252/609) couples with recurrent spontaneous abortion and in 34% (31/92) with infertility compared with 63% (27/43) of fertile couples. The frequency of lymphocytotoxic antibodies to paternal cells was significantly greater in the fertile population (27/143, 63%) (p < 0.0001) than in couples with recurrent spontaneous abortion (160/609, 26%) and in infertile couples (7/92, 8%). Mixed lymphocyte culture inhibitors were also more prevalent in sera from fertile women (19/43, 44%) compared with those with recurrent spontaneous abortion (122/609, 20%) and infertile women (4/92, 4%).

CONCLUSION

Human leukocyte antigen sharing does not predict pregnancy outcome, and the presence of lymphocytotoxic antibodies and mixed lymphocyte culture inhibitors is a function of the number and duration of pregnancies. More sensitive and specific assays are needed to identify alloimmunologic causes of reproductive disorders.

Studies of RFLP-inferred HLA-DR-DQ haplotypes in Danish women with recurrent fetal losses

Results of HLA-DR and -DQ typing by RFLP in 152 unrelated women with at least 3 unexplained fetal losses were compared with those of 210 normal controls. The overall distribution of DR-DQ phenotypes did not differ significantly between patients and controls. In a subgroup of 59 patients having had at least 4 fetal losses, a significantly higher number of patients than controls were DRw17,DQw2-positive (RR = 2.9, pcorrected less than 0.02). DR-DQ haplotypes which carry DQB1 alleles encoding an amino acid other than aspartic acid at codon 57 in the second exon (non-Asp57 haplotypes) have been reported to confer susceptibility to several immunologically-mediated diseases. We found that the total frequency of non-Asp57 haplotypes (other than DR7,DQw2 which has unique features) was significantly increased in patients (50.0%) compared with controls (39.3%) (p less than 0.005). In the total group of patients and in the group with at least 4 fetal losses, 22.4% and 32.2% respectively were homozygous non-Asp57/non-Asp57 compared with 13.3% among controls (RR = 1.9, p less than 0.025 and RR = 3.1, p less than 0.001, respectively). The results suggest that DRw17,DQw2 confers susceptibility to suffer recurrent fetal losses. However, it is possible that the HLA-associated susceptibility may be primarily conferred by DQ molecules lacking aspartic acid at codon 57 in the DQ beta chain.

Impact of histocompatibility antigens on pregnancy outcome

OBJECTIVE

The role of histocompatibility antigens in pregnancy outcome is controversial. This controversy may be because the initial studies were of small numbers or the patient groups were not homogeneous. The purpose of this study is to clarify these discrepant results by carrying out histocompatibility antigen typing and mixed lymphocyte culture on couples with idiopathic recurrent spontaneous abortion and by comparing results with those of fertile couples.

STUDY DESIGN

Sixty couples with at least three spontaneous abortions and 60 normal couples with at least two successful pregnancies were included. Histocompatibility antigen typing and mixed lymphocyte culture were performed by using the standard techniques. The data were analyzed statistically with the Fisher exact test and chi 2.

RESULTS

Our results failed to show any difference between normal and aborting couples with regard to HLA-A, HLA-B, and HLA-DR distribution or sharing or to mixed lymphocyte culture responsiveness.

CONCLUSION

Our study, along with other studies, emphasizes that the histocompatibility antigen system does not have an impact on pregnancy outcome.

Evaluation of immunological infertility

To evaluate the frequency with which immunological factors are associated with infertility, 92 couples with unexplained infertility were studied by using assays to detect anti-sperm antibodies (ASA), human leukocyte antigen tissue types (HLA), lymphocytotoxic antibodies (LCA), and inhibitors of mixed lymphocyte culture (MLC) and mouse blastocyst assay (MBA). Seventy-three of the women had blood assayed for antiphospholipid antibodies (APA). The frequencies of APA, ASA, LCA, inhibitors of MLC and MBA, as well as HLA associations previously reported to be related to infertility (B locus blanks, single DQ locus in offspring, greater than 1 DR sharing between mates) among 92 infertile couples were compared with those observed among 41 fertile control couples. No significant differences in the frequencies of APA, ASA, MBA, and HLA associations between fertile and infertile couples were observed. Fertile couples demonstrated the presence of wife anti-husband LCA and MLC inhibitors more frequently than did infertile couples (51% vs. 8%, P = 0.0001 and 29% vs. 4%, P = 0.002, respectively). While APA, ASA, HLA tissue typing, LCA, and MLC and MBA have been previously reported as being markers of autoimmune and alloimmune responses relating to reproductive outcome, the current data suggest that more specific markers are necessary to diagnose immunological components of infertility.

Tumour Necrosis Factor B Gene Polymorphism in Relation to Complotype in Couples with Spontaneous Abortions and in Control Families

NcoI restriction fragment length polymorphism (RFLP) of the tumour necrosis factor B (TNFB) gene gives two allelic fragments of 5.5 and 10.5 kb, corresponding to the TNFB*1 and TNFB*2 alleles, respectively. The frequencies of these alleles were analysed in 121 healthy Finns and 56 Finnish couples suffering from recurrent spontaneous abortions (RSA). In the healthy Finns the frequency of TNFB*1 was 37% and that of TNFB*2 63%, of which the frequency of TNFB*1 was significantly increased compared with the Danish population. No deviation was seen between the RSA couples and the Finnish controls. TNF genes are located in major histocompatibility complex class III region close to complement (BF, C4A and C4B) genes. Some complotypes associated most often with the TNFB*1 (S01, S30, S02) and some (S31, F320) with the TNFB*2 allele in the healthy Finns. The combination of the TNFB and the C4 'null' allele differed between the RSA couples and the Finnish controls.

Maintenance of multiallelic polymorphism at the MHC region

Models that purport to explain the maintenance of MHC polymorphism must be able to explain a variety of phenomena. (1) The range of MHC allele frequencies at some of the loci is very large, with some alleles quite common and many others rare, while at others the range of allele frequencies is far narrower. (2) MHC alleles and their frequencies often have long persistence times, in some cases tens of millions of years. (3) Random-mating populations appear to be in Hardy-Weinberg equilibrium for MHC. (4) There is no obvious, strong and consistent selection pressure yet detected that acts differentially on different MHC genotypes. (5) Because the allelic composition of the MHC polymorphism does change over evolutionary time, the MHC system must be capable of accommodating new alleles with similar properties without destruction of the equilibria that permit the maintenance of the older alleles. In this review I examined the degree to which a large number of models that have been proposed fit these criteria. These include heterosis, marginal overdominance, conditional heterosis, assortative mating, maternal-fetal incompatibility, molecular mimicry, minority advantage, pathogen adaptation, and optimum allele frequency models. Most of the models do poorly at accounting for a number of the above phenomena. The last class, optimum allele frequency models, have the most satisfactory set of properties. However, optimum allele frequency models require mechanisms that somehow "feed back" from the frequency of an allele in the population to the fitness of an organism carrying that allele. Thus, these models require that MHC polymorphisms be maintained by some type of group selection. Evidence for an against optimum allele frequency selection, and ways in which this type of selection might be detected experimentally, are presented.

Gene trees and the origins of inbred strains of mice

Extensive data on genetic divergence among 24 inbred strains of mice provide an opportunity to examine the concordance of gene trees and species trees, especially whether structured subsamples of loci give congruent estimates of phylogenetic relationships. Phylogenetic analyses of 144 separate loci reproduce almost exactly the known genealogical relationships among these 24 strains. Partitioning these loci into structured subsets representing loci coding for proteins, the immune system and endogenous viruses give incongruent phylogenetic results. The gene tree based on protein loci provides an accurate picture of the genealogical relationships among strains; however, gene trees based upon immune and viral data show significant deviations from known genealogical affinities.

Predictors of pregnancy success in repeated miscarriage

Factors that may have a bearing on subsequent pregnancy success or failure in patients with recurrent abortion were examined in 165 women with a history of three or more consecutive miscarriages in the first trimester. The overall success rate was 67.9%. Factors that were found to correlate significantly with success rate were length of abortion history, total number of abortions, interval from last miscarriage to present pregnancy, and whether there was any degree of subfertility. Logistic regression analysis showed that the abortion x years index and maternal age accounted for all the variation observed in our data. Where all other known causes of abortions are excluded, recurrent aborters can be subdivided into two populations--namely, those with a relatively good prognosis characterized by a short abortion history and absence of subfertility problems, compared to those with a poor prognosis namely those with a long abortion history or presence of subfertility problems. These data clearly demonstrate major differences in success rates in women depending on the number of abortions and the length of abortion history (abortion x year index), particularly in women over the age of 30 years.

Epidemiology of recurrent spontaneous abortion

With recent scientific advances leading to better understanding of the immunobiology of recurrent spontaneous abortion (RSA), interest has now focused upon the epidemiology of RSA. A cohort of 214 couples with a history of two or more consecutive abortions were studied for the prevalence of etiologic factors and association with other reproductive failures. The prevalence of causes of RSA in this cohort was compared with etiologic factors among 179 couples with a history of three or more consecutive abortions. The obstetrical histories of 214 women with RSA were analyzed for the total number of pregnancies, live births, stillbirths, spontaneous abortions, ectopic pregnancies, and hydatidiform moles. These numbers were compared with the expected frequency of each in the general population. The prevalence of etiologies among 214 with RSA were as follows: chromosomal-6%, anatomic-1%, hormonal-5%, immunologic-65%, and unexplained-23%. No differences in the prevalence of etiologic factors exist when couples with a history of two or more abortions are compared with three or more abortions. When the number of ectopic pregnancies, molar pregnancies, and stillbirths among 214 women with RSA were compared with the expected numbers, the odds ratios were 2.2 for ectopic pregnancies, 6.0 for molar pregnancies, and 2.3 for stillbirths. These data indicate that no difference in the prevalence of etiologies of RSA exist when couples with two or more abortions are compared with three or more and a comorbidity between RSA and other types of reproductive failure exists.

Probabilistic assessment of the HLA sharing of recurrent spontaneous abortion couples in the Japanese population

In spite of a number of investigations, the concept of human leukocyte antigen (HLA) sharing in recurrent spontaneous abortion (RSA) couples remains controversial. We introduced the basal antigen sharing rate (BSR) by the original mathematical approach using the gene frequency of all HLA specificities derived from our regional control population and applied this parameter for the comparison with RSA couples. RSA couples were classified into three subgroups; primary (3 or more consecutive abortions), secondary (3 or more consecutive abortions after 1 live birth), and potential (2 consecutive abortions) aborters. No significant differences between the HLA class I sharing rates (one or more antigens shared on a single locus) of the all RSA subgroups and the calculated BSRs were observed. In the HLA-DR and DQ loci, on the other hand, the antigen sharing rates of primary aborters were significantly higher than BSRs (p less than 0.01/DR, p less than 0.05/DQ). While potential aborters showed a result similar to that of the primary aborters, no significant antigen sharing of HLA class II was observed in secondary aborters. Our data suggest that BSR is a useful parameter for detection of significant HLA sharing in regional populations and the consecutive abortions that occurred primarily are certainly relevant to HLA class II sharing.

Immunotherapy for recurrent spontaneous abortions in a Chinese population

The efficacy of immunotherapy for the treatment of recurrent spontaneous abortions was tested in patients selected from the same ethnically homogeneous population of Chinese in Taiwan in whom the immunogenetics of gestational trophoblastic tumors and of recurrent spontaneous abortion had been studied. The patients, who included both primary and secondary aborters, were randomly assigned to three groups: those who were immunized with their own lymphocytes (controls) (49); those who were immunized with their husbands' lymphocytes (39); and those who were immunized with third party lymphocytes (11). The data were analyzed individually for the primary and secondary aborters and collectively for both groups combined. The number of babies born, the number of current pregnancies, and the number of recurrent abortions were not statistically significantly different between the control and the immunized groups, and a similar small number of congenital abnormalities (4-9%) occurred in both the control and immunized groups. The increase in the blocking effect for the mixed lymphocyte reaction was not related to the success of the postimmunization pregnancies. Thus, this study does not show any significant improvement in the rate of livebirths in women immunized with their husbands' lymphocytes or with third party lymphocytes compared to that in a placebo-controlled group of women.

HLA or HLA-linked genes reduce birthweight in families affected by idiopathic recurrent abortion

HLA typing was performed in 49 families, each containing at least one woman with a history of unexplained recurrent spontaneous abortion (RSA), and reproductive histories were recorded for the siblings. Abortion rate in sisters sharing two HLA haplotypes with the proband was significantly (p less than 0.01) increased, whereas abortion rates of brothers' wives seemed independent of the brothers' degree of HLA sharing with the proband. Birthweights of offspring of both the sisters and the brothers decreased with increasing HLA haplotype identity between the sibling and the proband (p = 0.05). The mean birthweight of infants of siblings sharing both parental haplotypes with the proband was 3158 g which was significantly (p less than 0.02) less than the average birthweight in Denmark (3417 g). Significantly (p less than 0.05) decreased mean birthweight in infants of brothers who were HLA-identical with the proband suggested that the disposition to growth retardation could be inherited with HLA also through the male gametes. It has been shown that, in their few successful pregnancies, women with RSA bear infants with a birthweight which is approximately 300 g less than normal. The present study demonstrated that the two obstetrical conditions, RSA and retarded fetal growth, share common genetic markers: HLA. It is suggested that HLA or HLA-linked genes causing growth retardation in fetuses are part of the putative complex of genes involved in the pathogenesis of recurrent abortion.

Sharing of human leukocyte antigens in primary and secondary recurrent spontaneous abortions

The prevalence of recurrent fetal loss and its relationship to sharing of human leukocyte antigens within couples was examined in a large, ethnically homogeneous Chinese population in Taiwan: 91 couples with primary recurrent spontaneous abortion, 32 couples with secondary recurrent spontaneous abortion, and 51 normal fertile couples. There was an excess of human leukocyte antigen sharing in both types of recurrent aborters. The primary aborters shared human leukocyte A and DQ antigens and three or more of the human leukocyte A, B, DR, and DQ antigens. The secondary aborters did not have an excess of sharing at any one locus but they did share three or more of the human leukocyte A, B, DR, and DQ antigens. There was no excess of antipaternal cytotoxic antibodies in any group of aborters, and the primary aborters had a lower level of mixed lymphocyte reaction blocking factor than normal couples or secondary aborters. Previous studies showed that couples in whom a gestational trophoblastic tumor developed in the woman shared human leukocyte B and DQ antigens and three or more of the human leukocyte A, B, DR, and DQ antigens. These studies provide substantial support for the role of recessive genes linked to the major histocompatibility complex in the pathogenesis of recurrent spontaneous abortions and of gestational trophoblastic tumors.

Association of maternal HLA haplotypes with recurrent spontaneous abortions

Histocompatibility typing was done on 63 women with idiopathic, recurrent abortions (greater than or equal to 3 consecutive, spontaneous abortions; summarized abortion rate: 92.8%), 112 of their full siblings and 101 parents. The distribution of full sisters sharing 2, 1 and 0 of the probands' haplotypes diverged from expected Mendelian segregation (p less than 0.05). Sisters sharing both the probands' haplotypes had an abortion rate of 59.1%, haploidentical sisters had an abortion rate of 25.0% whereas 6.3% of the pregnancies of the 0 haploidentical sisters had ended in miscarriage. The probands' HLA haplotypes included a significant (p less than 0.02) excess of HLA-A, B haplotypes which have previously been shown to exhibit features of positive linkage disequilibrium in Danes. Analysis of abortion rates among the probands and their siblings indicate that the idiopathic recurrent abortion syndrome and probably also the tendency to some sporadic abortions are inherited conditions determined by genes in the HLA region. The presented data may be compatible with an additive polygenic mode of inheritance with exclusive or predominant phenotypic expression in females controlled by an HLA linked spontaneous abortion susceptibility region (SASR).

The influence of the BoLA-A locus on reproductive traits in cattle

Associations between the major histocompatibility complex (MHC) and reproductive performance have been reported in humans, mice, rats, pigs and chickens. Only the A locus of the bovine major histocompatibility complex (BoLA-A) has been well characterized, and 42 alleles of this locus have been identified in American cattle. Four studies were conducted to examine the association between alleles of the BoLA-A locus and reproductive performance. Testis size, which is an indicator of early puberty and increased fertility in young bulls, was examined in 440 yearling bulls from nine breeds with a gene substitution model that included the effects of breed, sire, age of dam and age or weight of the bull. Estimated breeding value for twinning was examined with a gene substitution model with 204 cattle from a herd with a high frequency of twinning. Fertility of potential partners having BoLA-A locus alleles in common was examined in a prospective study involving 101 pure-bred Hereford cows mated by artificial insemination to four pure-bred Hereford bulls. The effect of homozygosity on birth weight, preweaning weight gain and post-weaning weight gain was estimated in a sample of 683 calves from nine breeds; 22% of the calves were apparently homozygous and 78% were heterozygous at the BoLA-A locus. There were significant and large effects of some BoLA-A locus alleles on paired testicular volume, but the analyses on the other traits did not show significant associations. Substitution of the W6.1 allele for the W9A allele reduced paired testicular volume by 150 +/- 44 cm3. The W6.1 allele has now been shown to influence a reproductive trait, a production trait and susceptibility to an economically important disease. Selection for these traits may influence the frequency of the large number of alleles at the BoLA-A locus.

Treatment of recurrent spontaneous abortion by immunization with paternal lymphocytes: correlates with outcome

Previous observations have suggested that defective recognition of fetal alloantigens by the maternal immune system is associated with recurrent pregnancy failure and that this may be prevented by boosting the maternal immune system with paternal or pooled third-party leukocytes. The mechanism whereby this process achieves success is not clear, and accordingly to explore this we immunized 28 couples with recurrent fetal loss with 80 x 10(6) paternal peripheral blood mononuclear leukocytes (PBML) and followed various immunological parameters. The couples studied, in whom 55% achieved a successful pregnancy, showed no increase in sharing of human lymphocyte antigen (HLA)-A, -B, or -DR antigens and no consistent evidence of a decreased mixed leukocyte reaction (MLR) or MLR plasma-blocking factors compared with control couples. Immunization did not alter these parameters but did induce antipaternal lymphocytotoxins, although the presence of the latter did not correlate with pregnancy outcome. There was a correlation between rapid conception after immunization and a subsequent successful pregnancy. A successful pregnancy also correlated with sustained postimmunization, postconception maternal antipaternal allospecific CD-8+ suppressor T cells. Although these findings provide overall evidence that immunization produces changes in the way in which the maternal immune system interacts with the fetus, larger numbers of couples and a higher dose of paternal lymphocytes will be needed to establish clearly whether this therapy works and its mechanism of action.

Histocompatibility antigens and habitual abortion

Eighty-five couples with habitual abortion were studied: 43 were primary aborters (i.e., had no advanced pregnancy beyond 20 weeks gestation), and 42 were secondary aborters. The only significant finding in primary female aborters was a reduction in the incidence of B35. In contrast, in secondary female aborters there was a reduction in the incidence of DR3 and A1/B8/DR3 and an increase in the degree of homozygosity of HLA B. In the male partners of primary aborters, there was a reduced incidence of DR3 and A1/B8/DR3. In addition, in male partners of both primary and secondary aborters, there was increased HLA-B homozygosity and increased frequency of DR4-5 phenotype. Increased sharing of HLA antigens between partners was not found to be significantly different from the control population. These findings emphasize that primary and secondary female aborters form distinct populations, which could explain differences in immunological responses to various antigens, including fetal-related antigens. The closely related findings in female secondary aborters and male partners of primary aborters are intriguing but cannot be explained. Whether or not these genetic markers bear any relationship to reproductive success remains to be determined.