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

Reproductive immunology in viviparous mammals: evolutionary paradox of interactions among immune mechanisms and autologous or allogeneic gametes and semiallogeneic foetuses

Literally, reproductive immunology was born in bovine on-farm reproduction where seminal experiments intended for developing methods for embryo transfer in cattle were performed. Actually, these experiments led to two of major concepts and fundamental principles of reproductive immunology using the bovine species as a model for biomedical research, namely the concept of acquired immunological tolerance and the paradox of the semiallogeneic bovine foetus whereby such organism can develop within an immunologically competent host. Peter Medawar, a scientist who together with Frank Macfarlande Burnet shared the 1960 Nobel Prize in physiology or medicine for discovery of acquired immunological tolerance, while studying dizygotic cattle twins, thereby giving birth to reproductive immunology. Also, these findings significantly influenced development of organ transplants and showed that using farm animals as models for studying transplantation immunology had general relevance for mammalian biology and health including those of humans. However, the interest for further research of the fascinating maternal immune influences on pregnancy and perinatal outcomes and of the prevention and treatment of immunologically mediated reproductive disorders in viviparous mammals of veterinary relevance by veterinary immunologists and reproductive clinicians have been very scarce regarding the application of nonspecific immunomodulatory agents for prevention and treatment of subfertility and infertility in pigs and cattle, but still broadening knowledge in this area and hold great potential for improving such therapy in the future. The aim of the current overview is to provide up-to-date information and explaining/translating relevant immunology phenomena into veterinary practice for specialists and scientists/clinicians in reproduction of animals.

HLA associations and HLA sharing in recurrent miscarriage: A systematic review and meta-analysis

PROBLEM

The aim of this meta-analysis was to evaluate whether specific maternal HLA alleles and HLA sharing of couples are associated with the occurrence of recurrent miscarriage (RM).

METHOD OF STUDY

A systematic literature search was performed for studies that evaluated the association between HLA alleles, HLA sharing and RM. RM was defined as three or more consecutive unexplained miscarriages and a control group was included of women with at least one live birth and no miscarriages in their history. Meta-analyses were performed and the pooled odds ratio (OR) was calculated.

RESULTS

We included 41 studies. Selection bias was present in 40 studies and information bias in all studies. Meta-analyses showed an increased risk of RM in mothers carrying a HLA-DRB1*4 (OR 1.41, 95% CI 1.05-1.90), HLA-DRB1*15 (OR 1.57, 95% CI 1.15-2.14), or a HLA-E*01:01 allele (OR 1.47, 95% CI 0.20-1.81), and a decreased risk with HLA-DRB1*13 (OR 0.63, 95% CI 0.45-0.89) or HLA-DRB1*14 (OR 0.54, 95% CI 0.31-0.94). Pooling results for HLA sharing showed that HLA-B sharing (OR 1.39, 95% CI 1.11-1.75) and HLA-DR sharing (OR 1.57, 95% CI 1.10-1.25) were both associated with the occurrence of RM.

CONCLUSION

Although the present systematic review and meta-analysis demonstrates that specific HLA alleles and HLA sharing are associated with RM, a high degree of bias was present and therefore observed results should be interpreted carefully.

Significant Compatibility Does Not Exist at the HLA-DQB Gene Locus in Couples With Unexplained Recurrent Abortions

The polymerase chain reaction-restricted fragment length polymorphism (PCR-RFLP) method was used for both examining compatibility at the HLA-DQB1 gene locus and determining HLA-DQ antigen polymorphism in spouses of unexplained recurrent abortions. Genomic DNA samples were prepared from peripheral mononuclear cells from patient and control couples. Two hundred and thirty base pair fragments of the second exon of the HLA-DQB genes were selectively amplified. Amplified DNAs were digested with the restriction endonucleases, Fok I, Hae III, Hha I, Rsa I and Sau3A I, and subjected to electrophoresis in a polyacrylamide gel. The RFLPs showed that habitual aborters and their husbands had neither significantly frequent alleles nor shared common alleles at the HLA-DQB locus when compared to the control group. Since significant HLA-DQB compatibility was not observed between the spouses and unexplained recurrent aborters, in order to determine whether or not HLA compatibility is responsible for the genesis of unexplained recurrent abortions, it is imperative to further examine the compatibility between other HLA gene loci.

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.

MHC class II DRB diversity, selection pattern and population structure in a neotropical bat species, Noctilio albiventris

Genes of the major histocompatibility complex (MHC) have a crucial role in the immune response of vertebrates, alter the individual odour and are involved in shaping mating preferences. Pathogen-mediated selection, sexual selection and maternal-fetal interactions have been proposed as the main drivers of frequently observed high levels of polymorphism in functionally important parts of the MHC. Bats constitute the second largest mammalian order and have recently emerged as important vectors of infectious diseases. In addition, Chiroptera are interesting study subjects in evolutionary ecology in the context of olfactory communication, mate choice and associated fitness benefits. Thus, it is surprising that they belong to the least studied mammalian taxa in terms of their MHC diversity. In this study, we investigated the variability in the functionally important MHC class II gene DRB, evidence for selection and population structure in the group-living lesser bulldog bat, Noctilio albiventris, in Panama. We found a single expressed, polymorphic Noal-DRB gene. The substitution pattern of the nucleotide sequences of the 18 detected alleles provided evidence for positive selection acting above the evolutionary history of the species in shaping MHC diversity. Roosting colonies were not genetically differentiated but females showed lower levels of heterozygosity than males, which might be a sign that the sexes differ in the selection pressures acting on the MHC. This study provides the prerequisites for further investigations of the role of the individual MHC constitution in parasite resistance, olfactory communication and mate choice in N. albiventris and other bats.

Molecular genetic studies on the compatibility of HLA class II alleles in patients with unexplained recurrent miscarriage in the Japanese population

It is hypothesized that patients having unexplained recurrent miscarriage lack an appropriate immune reaction against their partner's antigens, which means possible compatibility of HLA antigens between the patient couples. The conclusion, however, has not yet been achieved, so the purpose was to determine whether significant compatibility of HLA class II exists between the couples. The HLA-DRB1 and -DQB1 genotypes were determined using PCR-RFLP method in 91 patient couples and in 72 normal couples. The number of patient couples with zero-allele mismatch was not significantly different compared with that of control couples regarding HLA-DRB1 genotype and phenotype, as well as regarding HLA-DQB1 genotype and phenotype. While the number of patient couples with zero- and one-allele mismatch was significantly higher compared with that in control as to HLA-DR and -DQ phenotype (P=0.029 by Chi-square test). In conclusion, it is suggested that the compatibility of HLA class II antigens between couples might be involved in the genesis of unexplained recurrent miscarriage.

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.

Transmission of Parentally Shared Human Leukocyte Antigen Alleles and the Risk of Preterm Delivery

OBJECTIVE

Our objective was to examine our hypothesis that the transmission of parentally shared human leukocyte antigen (HLA) alleles to offspring increases the risk of preterm delivery.

METHODS

A population-based family study with participating children and their parents was conducted in Kaiser Permanente Medical Care Program, an integrated healthcare delivery system, in the Northern California Region. A total of 234 participants from 78 families with early preterm deliveries (35 weeks of gestation or greater) and 60 participants from 20 families with full-term births were included in the study. Buccal cells were collected from the first-born preterm cases and their parents to determine HLA-B (class I) and DRB1 (class II) types and the transmission of parental alleles to the offspring. The buccal samples were also collected from full-term deliveries to rule out possible segregation distortion at the studied HLA loci.

RESULTS

Compared with the expected transmission probability based on Mendel's laws (25%), transmission of parentally shared HLA-B or DRB1 alleles from both heterozygous parents to offspring (48% of 23 heterozygous parents) was associated with a more than 5-fold increased risk of preterm delivery (odds ratio 5.5; 95% confidence interval 1.2-51). Transmission of parentally shared HLA alleles from heterozygous mothers (83%) appears to be more important in the etiology of preterm delivery than transmission from fathers (57%). The transmission pattern of parentally shared HLA alleles in our full-term controls was almost identical to the expected pattern based on Mendel's laws and demonstrated no segregation distortion at those HLA loci.

CONCLUSION

Our findings provide evidence that the transmission of parentally shared HLA alleles may be an underlying mechanism for preterm delivery.

HLA-class I antigens in patients with unexplained recurrent abortion

In order to clarify the genetic background of recurrent spontaneous abortion, the frequency of HLA-A, -B, and -C alleles was analyzed in eighty-nine patients with a history of unexplained primary recurrent abortion. The frequency of each HLA-A, -B, and -C antigen allele was calculated in patients with recurrent abortion and their husbands, and compared with the frequencies in the general population represented by 207 individuals in the Niigata district of Japan. The incidence of individuals homozygous for the HLA-A, -B, and -C alleles was also compared between the patient group and the control group. The frequency of HLA-B35 in the patient group (5 of 89, 5.6%) was significantly lower than in the general population (40 of 207, 19.3%) (Odds Ratio, 0.25; 95% Confidence Interval, 0.09-0.65; P < 0.005; Pc, not significant). The frequencies of other HLA-A, -B, and -C alleles were not significantly different between the patient group and the general population. No significant difference in the frequency of HLA-A, -B, and -C alleles was observed between the husband group and the general population. The incidence of individuals homozygous for HLA-A, -B, or -C alleles in the patient group was not significantly different from the general population. The significantly lower frequency of HLA-B35 in patients with unexplained recurrent abortion suggests that the Th2-associated immune reactions may be lacking in such patients, as it has been reported that an enhanced Th2 response in conjunction with a decreased T Th1 response is a common immune reaction in HLA-B35-positive individuals.

Evidence for major histocompatibility complex-mediated effects on spermatogenesis in humans

Studies in fertile and infertile populations suggest an influence of genes of the major histocompatibility complex (MHC) on reproduction, although it remains unresolved if MHC-mediated effects on fertility are based on direct immunological or non-immunological effects of human leukocyte antigen (HLA) genes or rather on defects in MHC-associated non-HLA genes which affect gamete quality and embryonic development. We analysed allele frequencies for HLA class II loci DQA1, DQB1 and DRB1 and HLA class II haplotype frequencies in couples with tubal and andrological infertility who were treated with assisted reproductive techniques. Males with severe andrological infertility had significantly different allele frequencies for all three HLA loci when compared to males with normozoospermia, whereas no difference was found in the females. Differences in allele frequencies were stronger when only males whose partners achieved pregnancies after assisted reproduction treatment were compared. In those subgroups, we could also observe significant differences in three locus HLA class II haplotype frequencies. In summary, patients with male factor infertility differ in their HLA class II allele constitution from males with normozoospermia, which suggests that genes identical to or located in close vicinity to HLA class II genes may influence spermatogenesis and male gamete function.

Possible susceptibility of the HLA-DPB1*0402 and HLA-DPB1*04 alleles to unexplained recurrent abortion: analysis by means of polymerase chain reaction-restricted fragment length polymorphism method

PROBLEM

To clarify whether HLA-DP antigens are associated with patient population of unexplained recurrent abortion.

METHOD OF STUDY

The frequency of HLA-DPB1 alleles in patients with unexplained recurrent abortion, and the compatibility of HLA-DPB1 alleles between patient couples, were studied using a polymerase chain reaction (PCR)-restricted fragment length polymorphism (RFLP) method. Thirty patients who had a history of unexplained primary recurrent abortion, and their husbands, were typed for HLA-DPB1 genotype. Two hundred and ninety-nine base pair fragments from the second exon of HLA-DPB1 genes were selectively amplified using the PCR-primers. After amplification, the DNAs were digested with restriction endonucleases, and subjected to electrophoresis in a 12% polyacrilamide gel to determine HLA-DPB1 genotype.

RESULTS

The frequency of HLA-DPB1*0402 and DPB1*04 alleles in the patient group (n = 30) was significantly increased, as compared to that in the normal fertile women (n = 30). The frequency of HLA-DPB1*04 allele in the patient group was significantly increased, as compared to that in the general population (n = 112). No significant compatibility of HLA-DPB1 alleles could be observed between patient couples and normal fertile couples.

CONCLUSION

These findings suggest a possible new class II association with patient population of unexplained recurrent abortion.

Mechanisms of action of major-histocompatibility-complex-linked genes affecting reproduction

PROBLEM

To provide insight into the mechanisms of action of the major-histocompatibility-complex (MHC)-linked genes affecting reproduction.

METHOD OF STUDY

The data were obtained using a variety of cellular and molecular techniques in experimental animals and from population genetic studies in humans.

RESULTS

In the mouse, the preimplantation embryonic development (Ped) locus, whose functional gene is Q9, regulates fast and slow cleavage of the early embryo. There is also evidence for a growth and reproduction complex (Grc)-like region from serologic, molecular, and cytogenetic studies. In the human, the human leukocyte antigen (HLA)-G gene has been associated with an increased rate of embryonic cleavage in those embryos that express the HLA-G antigen. Sharing of HLA antigens in couples has been associated with recurrent spontaneous abortions, gestational trophoblastic tumors, and unexplained infertility. Detailed mapping studies showed that the genes responsible are not the HLA genes themselves, but genes closely linked to the HLA-DR-DQ-B genes. The HLA region genes can interact epistatically with the C3 allele of transferrin to increase the incidence of fetal loss. In the rat, the Grc region, which is closely linked to the MHC, has been associated with embryonic loss, growth defects, and susceptibility to chemical carcinogens. The Grc can interact epistatically with the tail anomaly lethal (Tal) gene or the hood restriction (Hre) gene to enhance these effects.

CONCLUSIONS

There are two basic mechanisms for the effects of MHC-linked genes on reproduction and development: individual gene effects (Ped [Q9], HLA-G) and extended genetic effects (MHC-linked genes in the rat [Grc] and in the human). The nature of these genetic effects, particularly the MHC-linked effects, can also provide some insight into the different theories of human origins: These effects are most consistent with the monogenic theory.

Clinical significance of morphologic and genetic examination of spontaneously aborted embryos

PROBLEM

In families with a history of multiple pregnancy losses, the prognosis of future pregnancies is critically dependent on recognizing an accurate pathogenesis of pregnancy loss.

METHOD OF STUDY

Morphological and genetic evaluation of products of conception provides necessary information for clinicians. Modern molecular cytogenetic techniques such as in situ hybridization and comparative genomic hybridization allow cytogenetic diagnosis even when aborted tissues are nonviable.

RESULTS

Correlation of morphological and cytogenetic findings allows distinction between developmental defects associated with chromosomal syndromes and other pathogenesis such as environmental teratogens, and Mendalian or multifactorial inheritance.

CONCLUSION

Pathologists have the responsibility of ensuring that the answers to questions, such as why the failure occurred or whether there is any increased chance of having an abnormal liveborn infant in a future pregnancy, are obtained and that the information is communicated to the parent's obstetrician, geneticist, and family physician.

Analyses of HLA-DQ alleles in recurrent spontaneous abortion (RSA) couples

PROBLEM

The influence of HLA sharing on pregnancy outcome is controversial. In renal transplantation, HLA-DQB1 donor-recipient mismatches have been shown beneficial for long-term transplant success. Since pregnancy is defined as Nature's allograft, we investigated the relevance of HLA-DQ mismatching in normal reproducing couples compared to couples experiencing RSA.

METHOD

Unexplained RSA couples referred to our laboratory for immunological testing were classified by immunological findings and obstetrical history. Primary RSA couples shared > or = 2 HLA-A, B, or DR antigens, had no cytotoxic anti-paternal antibodies, and no gestation beyond 20 weeks. Secondary RSA couples had cytotoxic anti-paternal antibodies and RSA after a live birth. HLA-DQA1 and DQB1 alleles were identified by PCR-SSP.

RESULTS

No differences in DQA1 and DQB1 mismatch were observed among RSA patients and controls. DQA1-DQB1 haplotype mismatches were not different among the three groups of couples.

CONCLUSIONS

In contrast to renal transplant, HLA-DQ incompatibility did not differ among RSA couples compared with successful reproducing couples.

Non-random fertilization in mice correlates with the MHC and something else

One evolutionary explanation for the success of sexual reproduction assumes that sex is an advantage in the coevolutionary arms race between pathogens and hosts. Accordingly, an important criterion in mate choice and maternal selection thereafter could be the allelic specificity at polymorphic loci involved in parasite-host interactions, e.g. the MHC (major histocompatibility complex). The MHC has been found to influence mate choice and selective abortions in mice and humans. However, it could also influence the fertilization process itself, i.e. (i) the oocyte's choice for the fertilizing sperm, and (ii) the outcome of the second meiotic division after the sperm has entered the egg. We tested both hypotheses in an in vitro fertilization experiment with two inbred mouse strains congenic for their MHC. The genotypes of the resulting blastocysts were determined by polymerase chain reaction. We found nonrandom MHC combinations in the blastocysts which may result from both possible choice mechanisms. The outcome changed significantly over time, indicating that a choice for MHC combinations during fertilization may be influenced by one or several external factors.

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.

Role of the major histocompatibility complex region in reproduction, cancer, and autoimmunity

PROBLEM

A diverse body of evidence indicates that there is an association among reproductive failure, development, cancer, and autoimmunity. The evidence for the relationship of genes linked to the major histocompatibility complex to these diseases will be evaluated.

METHODS

The published results of both experimental studies in animals and of clinical observations in humans will be summarized and analyzed.

RESULTS

Experimental studies in the rat have demonstrated a relationship between the MHC-linked region and growth, development, and susceptibility to chemical carcinogens. Data from other species support these observations. Clinical studies in humans have demonstrated an association between the MHC region and recurrent spontaneous abortions and a variety of other diseases; between recurrent spontaneous abortion and several autoimmune diseases; and between isolated populations and deficiencies of HLA homozygotes.

CONCLUSIONS

Genes in the MHC-linked region play an important role in the control of reproduction, growth and development, and susceptibility to a variety of diseases.

Influence of histocompatibility antigens in recurrent spontaneous abortion couples and on their reproductive performances

PROBLEM

To determine if human leukocyte antigens (HLA) play any role in the aetiology of recurrent spontaneous abortion (RSA), a substantial group of RSA couples were studied, and their reproductive performances in a 3-year follow-up recorded.

METHODS

HLA typing was performed for HLA-A, -B, and DR antigens in both partners of 75 couples with unexplained RSA, and compared with a control group of 30 fertile couples that never experienced abortion. A further 57 couples of this group were studied for their reproductive performance in a 3-year follow-up, and subdivided into three subgroups: 1) couples that achieved successful pregnancy during the follow-up, and subdivided into three subgroups: 1) couples that achieved successful pregnancy during the follow-up; 2) couples that experienced abortion and no livebirth during the follow-up; and 3) couples that experienced infertility during the follow-up.

RESULTS

There were no significant differences for antigen frequency in all the different HLA loci, and HLA antigen sharing between all the RSA couples and controls. Significant increase of sharing for HLA-DR locus was observed in the couples that aborted during the follow-up with respect to the couples that achieved livebirth and controls (P < 0.03 and P < 0.02 respectively), and significantly increased frequency of B44, DR5 antigen combination in the same comparison (P < 0.03). No significant differences were observed in terms of the interval between conceptions in couples without antigen sharing with respect to couples with 1, 2 or more antigens shared, and antigen sharing in Locus A, B or DR.

CONCLUSIONS

The results suggest that gene(s) disadvantageous for reproduction may exist between the HLA-B and -DR chromosomal region which influences the pregnancy outcome in RSA couples, and that HLA-antigen sharing itself does not influence the outcome.

Decidual natural killer cytotoxicity decreased in normal pregnancy but not in anembryonic pregnancy and recurrent spontaneous abortion

PROBLEM

The natural killer (NK) cell activity is depressed in the decidua of early normal pregnancy. Recently Morii et al. (Am J Reprod Immunol 1993;29:1-4) found that all early intradecidual CD3+ T cells expressed either T cell receptor (TCR) alpha/beta or gamma/delta but that the expression of the CD3+/TCR complex was down-regulated.

METHOD

To test whether these changes in decidual cellular immunity are different among normal pregnancy, anembryonic pregnancy and recurrent spontaneous abortion, we examined the immune cell subpopulations in the decidua from these three types of pregnancy using flow cytometry and an NK cytotoxicity assay.

RESULTS

Intradecidual CD3+ T cells expressed either TCR alpha/beta or gamma/delta, and the level of expression of the CD3/TCR complex was down-regulated in normal pregnancy, anembryonic pregnancy, and recurrent spontaneous abortion. Although the relative proportion of decidual NK cells was increased to approximately the same extent in all three types of pregnancy, decidual NK activity was higher in anembryonic pregnancies and in recurrent spontaneous abortions than it was in normal pregnancies.

CONCLUSION

Decidual NK cell responses are different in anembryonic pregnancies and in recurrent spontaneous abortions than in normal pregnancies. Whether this difference is pathogenic or is the response to a dead embryo remains to be elucidated.

Nucleotide sequence and structural analysis of the rat RT1.Eu and RT1.Aw3l genes, and of genes related to RT1.O and RT1.C

A cDNA library was constructed using mRNA isolated from the R21 strain of rats which have the major histocompatibility complex (MHC) haplotype RT1.AlBlDlEu and the growth and reproduction complex (grc) genotype grc+. The cDNA clones that hybridized with the class I probes pAG64c and pARI.5 and were 1.3-1.7 kilobases were selected. Full-length clones were identified by sequencing partially the 5' and 3' ends of each clone, by the presence of a start codon at the 5' end, and by a polyadenylation sequence at the 3' end. The full-length cDNA clones were examined for in vitro transcription by transfection into human CIR cells using electroporation, and expression was detected by flow cytometry using monoclonal antibodies specific to the heavy chains and polyclonal antibody to beta 2-microglobulin. The RT1.Eu gene was transcribed and expressed optimally, and its nucleotide and deduced amino acid sequences differed significantly from the RT1.Aa, RT1.A(l), RT.Au, LW2, and 11/3R genes but only slightly from the RT1.K gene. The high level of sequence similarity between RT1.Eu and RT1.K suggests that the two genes may have originated from a common ancestral gene. In addition, three new genes (RT1.Aw3l, RT1.C-type, and RT1.O-type) were identified. The RT1.Aw3l gene is almost identical to RT1.A(l) with the exception of an in frame deletion of 21 nucleotides in exon 2 leading to a 7 amino acid deletion in the alpha 1 domain of the deduced amino acid sequence and 11 nucleotide substitutions and insertions in the rest of the sequence. It transcribed optimally, but no significant expression was detected. The RT1.C-type gene 119 is very similar (97%) to the LW2 gene in the 3' untranslated region, which suggests that it is in the RT1.C region. It transcribed optimally, but no significant expression was detected. The RT1.O-type gene 149 has all the features of a class Ib gene, but a premature stop codon in the alpha 1 domain causes incomplete translation. Its in vitro transcription was very low, and no expression was detected. These studies, combined with previous work, indicate that in the MHC of the R21 strain three class Ia genes (Eu, A(l), Aw3l) and three class Ib genes (C-type, O-type, N) are transcribed but only two class Ia genes (Eu, A(l)) are expressed.

MHC-dependent mate preferences in humans

One substantial benefit of sexual reproduction could be that it allows animals (including humans) to react rapidly to a continuously changing environmental selection pressure such as coevolving parasites. This counteraction would be most efficient if the females were able to provide their progeny with certain allele combinations for loci which may be crucial in the parasite-host arms race, for example the MHC (major histocompatibility complex). Here we show that the MHC influences both body odours and body odour preferences in humans, and that the women's preferences depend on their hormonal status. Female and male students were typed for their HLA-A, -B and -DR. Each male student wore a T-shirt for two consecutive nights. The next day, each female student was asked to rate the odours of six T-shirts. They scored male body odours as more pleasant when they differed from the men in their MHC than when they were more similar. This difference in odour assessment was reversed when the women rating the odours were taking oral contraceptives. Furthermore, the odours of MHC-dissimilar men remind the test women more often of their own actual or former mates than do the odours of MHC-similar men. This suggests that the MHC or linked genes influence human mate choice today.

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.

Lack of evidence for a role of HLA-DP in unexplained recurrent spontaneous abortion

Using the "Polymerase Chain Reaction-Sequence Specific Oligoprobes" (PCR-SSOp) technique, we studied the HLA-DPB locus in both partners of 59 couples with a history of three spontaneous abortions, and of 38 control couples in order to determine the role of this centromeric region of the major histocompatibility complex (MHC) in the immune reaction needed for a favorable course of pregnancy. As no particular phenotypes were noted, and also neither excessive HLA-DP homozygosity in sterile women nor excessive HLA-DP allele sharing between sterile partners, this MHC class II sub-region would seem to play no role either directly or by linkage disequilibrium, in the development of normal pregnancy.

Mate choice and maternal selection for specific parasite resistances before; during and after fertilization

As Hamilton & Zuk pointed out, some loci may be of special importance for sexual selection because they play a crucial role in the co-evolution between parasites and hosts. In previous work I have tried to extend Hamilton & Zuk's parasite hypothesis for sexual selection, partly by including findings of immunologists and endocrinologists: in some species, handicapping signals may specifically reveal the current needs of the immune system which depends on the host's susceptibilities to different parasites. In other species, depending on the constellation of some key variables, non-handicapping signals could directly reveal the identity of resistance genes. Despite the general conflict of interests between the sexes, sexual selection may, in these cases, lead to signallers (i.e. mostly the males) focusing on improving their offspring's survival chances instead of trying to maximize their number. Males achieve this by allowing choosy females to optimize costs and benefits of each resistance. Both parts of the extended parasite hypothesis suggest that female choice for specific heritable matequalities aim to optimize the resistance genetics of the unfertilized eggs. However, intersexual selection could go further than just choosing a mate. Here, I list the possible selection levels at which the mother and/or her ova could select for specific sperm haplotypes before, during and after the formation of the zygote. For many of these possible selection levels, evidence suggests that selection after mating might favour heterozygosity or even certain specific allele combinations at loci which are involved in the parasite-host co-evolution (e.g. the major histocompatibility complex or the transferrin locus).

Sharing of human leukocyte antigens in couples with unexplained infertility affects the success of in vitro fertilization and tubal embryo transfer

OBJECTIVE

The purpose was to test further our hypothesis that genes, or genetic defects, linked to the major histocompatibility complex affect reproduction by correlating human leukocyte antigen sharing with the success or failure of in vitro fertilization and tubal embryo transfer in couples having unexplained infertility.

STUDY DESIGN

Seventy-six couples with unexplained infertility who failed superovulation and intrauterine insemination at least three times were typed for human leukocyte antigens and treated by in vitro fertilization and tubal embryo transfer. The results were correlated with the sharing of human leukocyte antigens in the couples.

RESULTS

Thirty-four of the women had successful pregnancies, 36 did not become pregnant, and six became pregnant but aborted shortly thereafter. There was a highly significant excess of human leukocyte antigen sharing in the couples who failed treatment: three of the A, B, DR, and DQ antigens (p = 0.015) or two of the B, DR, and DQ antigens (p = 0.015). No specific human leukocyte antigen alleles were present in excess.

CONCLUSIONS

Genes, or genetic defects, linked to the major histocompatibility complex significantly affect the success of in vitro fertilization and tubal embryo transfer just as they affect the prevalence of recurrent spontaneous abortion, cancer, and congenital anomalies. It appears as if the critical genes, or genetic defects, are located in the B-DR-DQ region of the major histocompatibility complex.

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.

A major histocompatibility complex-linked locus in the rat critically influences resistance to diethylnitrosamine carcinogenesis

Major histocompatibility complex (MHC)-linked deletions in the rat are associated with defects in growth and development and increased susceptibility to chemical carcinogens. The present study maps a locus critical for determining susceptibility to diethylnitrosamine (DEN) carcinogenesis by using two groups of MHC-recombinant rats congenic for the MHC and its linked region. Resistance to DEN segregates with a locus (rcc+) that maps between RT1.E and ft, and its homozygous loss markedly increases susceptibility to DEN. Non-MHC genes do not significantly influence the susceptibility of these strains to DEN. The existence of the rcc locus adds support to our hypothesis that some genes in the MHC-linked region play a major role in both normal and abnormal growth.

MAJOR HISTOCOMPATIBILITY COMPLEX LOCATED COMPLEMENT C4 AND STEROID 21-HYDROXYLASE GENE REARRANGEMENTS IN COUPLES WITH RECURRENT SPONTANEOUS ABORTIONS

Major Histocompatibility Complex (MHC) class III located complement C4 and steroid 21-hydroxylase (21OH) genes, which form various deletion and duplication units, were studied by TaqI Restriction Fragment Length Polymorphism (RFLP) in 58 Finnish couples who suffered recurrent spontaneous abortions (RSA). The gene rearrangements found in the RSA couples did not differ from those in the controls.

The role of blocking factors and antipaternal lymphocytotoxic antibodies in the success of pregnancy in patients with recurrent spontaneous abortion

OBJECTIVE

To elucidate the role of mixed lymphocyte reaction blocking factors (BF) and complement-dependent antipaternal lymphocytotoxic antibodies on the outcome of pregnancy in unexplained recurrent spontaneous aborters.

DESIGN

A controlled study of immunotherapy in which the treated group was immunized with the husband's or a third party donor's lymphocytes and the control group received autologous lymphocytes.

SETTING

Tertiary care institution.

PATIENTS

Forty-three patients in the control group and 48 patients in the treated group.

INTERVENTION

The before and after immunization levels of BF and antipaternal lymphocytotoxic antibodies were measured.

MAIN OUTCOME MEASURES

The existence or changing pattern of BF and antipaternal lymphocytotoxic antibodies levels before and after immunization had no influence on the pregnancy outcome in either group of patients.

CONCLUSION

Neither BF nor antipaternal lymphocytotoxic antibodies is essential for successful pregnancy. They probably reflect the immunological response of the mother to exposure to fetal antigens.

Physical mapping of the MHC and grc by pulse field electrophoresis

The development of the physical map of the major histocompatibility complex of the rat was undertaken using pulse field gel electrophoresis of fragments of genomic DNA from the BIL/2 (grc+) and BIL/1 (grc-) strains obtained primarily from single and double digests with the enzymes Mlu I, Not I, and Sfi I and hybridized with a variety of mouse, rat, and human probes. Both strains are maintained by inbreeding the BIL heterozygote (forced heterozygosity; F31); hence, their differences lie almost entirely in the MHC-grc regions. The MHC-grc region was contained in five fragments of DNA comprising 3000-3200 kilobases (kb); thus, its size appears to be closer to that of the human MHC than to that of the mouse MHC. This distance may be an underestimate of the size of the entire region, however, because the cluster of class I loci in the RT1. A region could not be defined in detail in this study. The most striking difference between the BIL/2 strain, which has normal growth and reproductive characteristics, and the BIL/1 strain, which has growth and reproductive defects and an enhanced susceptibility to chemical carcinogens, is a deletion of approximately 70 kb in the latter strain. The studies on grc+ and grc- strains suggest that the phenotypic defects of the grc- strains may be due to the loss of genes that are normally present in this deleted region.

The role of immunization treatment in preventing recurrent abortion

Published reports of controlled studies of immunization treatment in recurrent abortion have not shown any ability of either third-party cells or the husband's cells to prevent further abortions, whereas preliminary results of ongoing studies speak in favor of a beneficial effect of third-party cells. However, the lack of significant differences so far does not prove that immunotherapy in habitual abortion is ineffective, because all of these studies include too few patients in each group to give any conclusive results. Only a mega-trial could evaluate the efficacy and side effects of leukocyte immunotherapy. Such controlled studies are needed to clarify the true benefits, risks, and limitations of immunization treatment in recurrent abortion. Factors such as appropriate inclusion criteria, the time relationship between immunization and the next pregnancy, the number of immunizations required, the cell source and cell doses need to be established. Until this additional information is available this treatment should not be considered routinely indicated. This approach should be restricted to a few centers in order to provide maximal possibilities for collection and evaluation of the data.

The prevalence of recurrent spontaneous abortions, cancer, and congenital anomalies in the families of couples with recurrent spontaneous abortions or gestational trophoblastic tumors

This study extends our previous work on the genetics of recurrent spontaneous abortion and of gestational trophoblastic tumors in an ethnically homogeneous population of Chinese in Taiwan by comparing the prevalence of recurrent spontaneous abortions, cancer, and congenital anomalies in the first-, second-, and third-degree relatives of the index couples to that of normally fertile couples from the same population. The rationale for this study was to provide another test for our hypothesis that genes linked to the major histocompatibility complex are responsible for the diseases in the index couples. If they are, these genes should segregate with a higher frequency in the relatives of the index couples than in the relatives of normally fertile couples and lead to a higher prevalence of these diseases in the extended families. Such a difference was found and adds support to our hypothesis that major histocompatibility complex-linked genes affect growth, development, and susceptibility to cancer.

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.