The Early Care Model for Initiation of Perinatal Care: "I Actually Felt Listened To"

Early access to prenatal care is a crucial component in reducing poor perinatal outcomes. Institutional barriers such as insurance enrollment, clinic wait times, and systemic racism dramatically influence perinatal care engagement. The Early Care model seeks to address these barriers through a collaborative care model with licensed midwives and certified nurse-midwives. In contrast to traditional models of prenatal care in which the first visit is deferred until gestational age allows for a dating ultrasound, the Early Care model allows for care to be initiated at any gestation. Patients are offered accessible telehealth early pregnancy appointments for thorough assessment of clinical and social needs to better meet each person's unique and diverse experiences. Patients can receive timely referrals for emergent clinical and social needs, as well as education about all care options. This model promotes improved outcomes and decreased disparities, as well as broader awareness of midwifery care. This article provides an overview of the Early Care model experience.

The effect of testosterone on ovulatory function in transmasculine individuals

BACKGROUND

An estimated 1.4 million persons in the United States identify as transgender or nonbinary, signifying that their gender identity does not correspond with their assigned sex at birth. Individuals assigned female at birth may seek gender-affirming hormone therapy with testosterone. No studies have directly examined ovulatory function in transmasculine individuals using injectable testosterone.

OBJECTIVES

Our primary objective was to determine the effect of testosterone on ovulatory suppression in transmasculine individuals. Secondary objectives were to determine predictors of ovulation in transmasculine individuals on testosterone, and to assess the effect of testosterone on antimüllerian hormone.

MATERIALS AND METHODS

This prospective observational study recruited participants from a community clinic that provides gender-affirming hormone therapy. Enrolled individuals were assigned female at birth and were currently using or seeking to initiate masculinizing therapy with injectable testosterone esters (transmasculine individuals). Over a 12-week study period, participants collected daily urine samples for pregnanediol-3-glucoronide testing and completed daily electronic bleeding diaries. We assessed monthly serum mid-dosing interval testosterone, estradiol and sex hormone binding globulin, and antimüllerian hormone values at baseline and study end. Ovulation was defined as pregnanediol-3-glucoronide greater than 5 μg/mL for 3 consecutive days. The primary outcome was the proportion of participants who ovulated during the study period. We examined predictors of ovulation such as age, length of time on testosterone, serum testosterone levels, body mass index, and bleeding pattern.

RESULTS

From July to November 2018, we enrolled 32 individuals; 20 completed the study (14 continuing testosterone users, 6 new users). Median age was 23 years (range 18-37 years). Bleeding or spotting during the study period was noted by 41% of participants (13/32). Among continuing users, median testosterone therapy duration was 11 months (range 1-60 months). A single ovulation was observed out of a total of 61 combined months of testosterone use; however, several transient rises in pregnanediol-3-glucoronide followed by bleeding episodes were suggestive of 7 dysfunctional ovulatory cycles among 7 individuals. There was no difference in antimüllerian hormone from baseline to 12 weeks between participants initiating testosterone and continuing users of testosterone. We did not have the power to examine our intended predictors given the low numbers of ovulatory events, but found that longer time on testosterone and presence of vaginal bleeding over 12 weeks were associated with transient rises in pregnanediol-3-glucoronide.

CONCLUSION

This study suggests that testosterone rapidly induces hypothalamic-pituitary-gonadal suppression, resulting in anovulation in a proportion of new users. Importantly, these data also suggest that some long-term testosterone users break through the hormonal suppression and experience an ovulatory event, thereby raising concerns pertaining to the need for contraception in transmasculine individuals engaged in sexual intercourse with sperm-producing partners. Given the small number of overall participants, this work is hypothesis generating. Larger studies are needed to confirm and to clarify these findings.

A Survey of Midwives' Attitudes Toward Men in Midwifery

INTRODUCTION

The midwifery profession in the United States demonstrates a significant lack of diversity. The critical need to address the lack of racial and ethnic diversity in the midwifery workforce is well recognized; little attention, however, has been given to gender diversity. This study focused on gender diversity within midwifery, specifically with regard to men who are midwives. Nearly 99% of midwives in the United States are women. No research has previously explored the attitudes of the predominantly female midwifery workforce toward its male members.

METHODS

An invitation to an internet survey was sent to the American College of Nurse-Midwives (ACNM) membership. Quantitative and open-ended questions assessed attitudes toward and experiences with male midwives, whether members thought men belong in the profession, whether gender impacts quality of care, if ACNM should facilitate gender diversification, and whether exposure to male midwives impacts attitudes toward gender diversification. Data analysis of qualitative responses used a qualitative description methodology to identify common themes.

RESULTS

Six thousand, nine hundred sixty-five surveys were distributed, and 864 participants completed the survey. Respondents reported beliefs that men belong in midwifery (71.4%), that gender does not affect quality of care (74%), and that ACNM should support gender diversity (72%). Respondents' perspectives revealed 3 dichotomous themes pertaining to the core nature of midwifery and how men fit within the profession: 1) inclusion versus exclusion, 2) empowerment versus protection, and 3) sharing with versus taking from. Often, the same respondent expressed both aspects of the dichotomy simultaneously.

DISCUSSION

This study contributes new information about midwives' attitudes and beliefs toward gender diversity in midwifery in the United States. The values of professionalism, tradition, feminism, protection, and diversification inform participant responses. Findings support efforts toward gender diversification and have implications for implementation in education and practice.

Placental expression of major histocompatibility complex class I in bovine somatic clones

Abnormally increased placental expression of major histocompatibility complex class I (MHC-I) molecules at the trophoblastic surface has been suggested previously to be the cause of early fetal loss in nuclear transfer (NT) bovine pregnancies. Here, we report the lack of expression of MHC-I at the trophoblastic surface at D30 and D60 and in placentomes from D60 to term in placentas obtained by NT from three different genotypes and by artificial insemination, whatever the outcome of the pregnancy. MHC-I expression was assessed by immunohistochemistry using four different antibodies, including a novel beta2-microglobulin antibody. The MHC-I type of the clones was established using reference strand-mediated conformation analysis (RSCA); however, since it proved problematic to type the recipient animals in the same way, outcome of pregnancy could not be related to MHC compatibility. In conclusion, the present study provides no evidence to support abnormal expression of MHC-I on the trophoblastic surface in clones as a major cause of fetal loss during pregnancy after NT.

The E5 oncoprotein of BPV-4 does not interfere with the biosynthetic pathway of non-classical MHC class I

The major histocompatibility complex (MHC) class I region in mammals contains both classical and non-classical MHC class I genes. Classical MHC class I molecules present antigenic peptides to cytotoxic T lymphocytes, whereas non-classical MHC class I molecules have a variety of functions. Both classical and non-classical MHC molecules interact with natural killer cell receptors and may under some circumstances prevent cell death by natural killer cytotoxicity. The E5 oncoprotein of BPV-4 down-regulates the expression of classical MHC class I on the cell surface and retains the complex in the Golgi apparatus. The inhibition of classical MHC class I to the cell surface results from both the impaired acidification of the Golgi, due to the interaction of E5 with subunit c of the H+ V-ATPase, and to the physical binding of E5 to the heavy chain of MHC class I. Despite the profound effect of E5 on classical MHC class I, E5 does not retain a non-classical MHC class I in the Golgi, does not inhibit its transport to the cell surface and does not bind its heavy chain. We conclude that, as is the case for HPV-16 E5, BPV-4 E5 does not down-regulate certain non-classical MHC class I, potentially providing a mechanism for the escape of the infected cell from attack by both cytotoxic T lymphocytes and NK cells.

The E5 protein of BPV-4 interacts with the heavy chain of MHC class I and irreversibly retains the MHC complex in the Golgi apparatus

BPV-4 E5 inhibits transcription of the bovine MHC class I heavy chain (HC) gene, increases degradation of HC and downregulates surface expression of MHC class I by retaining the complex in the Golgi apparatus (GA). Here we report that transcription inhibition can be alleviated by interferon treatment and the degradation of HC can be reversed by treatment with inhibitors of proteasomes and lysosomes. However, the inhibition of transport of MHC class I to the cell surface is irreversible. We show that E5 is capable of physically interacting with HC. Together with the inhibition of the vacuolar ATPase (due to the interaction between E5 and 16k subunit c), the interaction between E5 and HC is likely to be responsible for retention of MHC class I in the GA. C-terminus deletion mutants of E5 are incapable of either downregulating surface MHC class I or interacting with HC, establishing that the C-terminus domain of E5 is important in the inhibition of MHC class I.

Characterisation of CTL and IFN-γ synthesis in ponies following vaccination with a NYVAC-based construct coding for EHV-1 immediate early gene, followed by challenge infection

Equine herpesvirus-1 (EHV-1) is a ubiquitous pathogen of horses, which continues to cause respiratory and neurological disease and abortion, despite the widespread use of vaccines. Cell mediated immunity (CMI) is thought to play a major role in protection against infection with EHV-1. The aim of this study was to characterise the virus-specific CMI response in ponies vaccinated with vP1014, a vaccinia-based construct (NYVAC) coding for the immediate early gene (gene 64) of EHV-1. This gene product is a CTL target protein for an equine MHC class I allele expressed on the A3 haplotype. EHV-primed yearling ponies expressing this haplotype were vaccinated once (n = 1), three (n = 1), or four times (n = 2), and one pony was kept as an unvaccinated control. Cytotoxic T lymphocyte (CTL) activity and interferon gamma (IFN-gamma) synthesis were measured before and after vaccination and challenge infection with EHV-1. Multiple immunisations with vP1014 resulted in increased CTL activity and IFN-gamma synthesis specific for EHV-1 compared with unvaccinated or singly vaccinated ponies. The phenotype of EHV-1 specific T-cells synthesising IFN-gamma was also modified by immunisation. In the unvaccinated pony, the predominant population synthesising IFN-gamma after EHV-1 stimulation was CD8alpha+. In contrast, multiply vaccinated ponies demonstrated an increased proportion of CD8alpha- T-cells synthesising IFN-gamma. The results demonstrated that vaccination with a NYVAC-based construct coding for gene 64 stimulated CMI. This immune response alone did not protect against challenge infection. However, the study does illustrate that vaccinia-based vaccines can stimulate CMI in the horse and may therefore contribute to protection against disease caused by EHV-1.

Novel classical MHC class I alleles identified in horses by sequencing clones of reverse transcription-PCR products

Improved typing of horse classical MHC class I is required to more accurately define these molecules and to extend the number identified further than current serological assays. Defining classical MHC class I alleleic polymorphism is important in evaluating cytotoxic T lymphocyte (CTL) responses in horses. In this study, horse classical MHC class I genes were analyzed based on reverse transcription (RT)-PCR amplification of sequences encoding the polymorphic peptide binding region and the more conserved alpha 3, transmembrane and cytoplasmic regions followed by cloning and sequencing. Primer sets included a horse classical MHC class I-specific reverse primer and a forward primer conserved in all known horse MHC class I genes. Sequencing at least 25 clones containing MHC class I sequences from each of 13 horses identified 25 novel sequences and three others which had been described. Of these, nine alleles were identified from different horses or different RT-PCR and 19 putative alleles were identified in multiple clones from the same RT-PCR. The primer pairs did not amplify putative non-classical MHC class I genes as only classical MHC class I and related pseudogenes were found in 462 clones. This method also identified classical MHC class I alleles shared between horses by descent, and defined differences in alleles between horses varying in equine leukocyte antigen (ELA)-A haplotype as determined by serology. However, horses sharing ELA-A haplotypes defined by serotyping did not always share cDNA sequences, suggesting subhaplotypic variations within serologically defined ELA-A haplotypes. The 13 horses in this study had two to five classical MHC class I sequences, indicating that multiple loci code for these genes. Sequencing clones from RT-PCR with classical MHC class I-specific primers should be useful for selection of haplotype matched and mismatched horses for CTL studies, and provides sequence information needed to develop easier and more discriminating typing procedures.

Control of expression of major histocompatibility complex genes in horse trophoblast

In most mammals, the fetus limits its presentation of paternal antigens to the mother by suppressing the cell-surface expression of proteins of the major histocompatibility complex (MHC) on trophoblast. In the horse, however, functional, polymorphic MHC class I antigens are expressed at high levels on the invasive trophoblast cells of the chorionic girdle between Days 32 and 36 of pregnancy, although not on the adjacent noninvasive trophoblast of the chorion and allantochorion membranes. In this study, the control of MHC class I gene expression was investigated in invasive and noninvasive horse trophoblast, and the MHC class I loci expressed by invasive trophoblast were identified. Northern blot hybridization of Day 33-34 conceptus tissue revealed both transcriptional and posttranscriptional regulation of cell-surface MHC class I expression in horse trophoblast. The invasive MHC class I-positive trophoblast showed levels of steady-state mRNA nearly as high as those in lymphoid tissues from adult horses, whereas noninvasive MHC class I-negative trophoblast also contained transcripts for MHC class I, but at lower levels similar to those present in adult horse nonlymphoid tissue. We also cloned and sequenced polymerase chain reaction products from the transmembrane and cytoplasmic regions of MHC class I transcripts in chorionic girdle and lymphocytes, and determined that horse invasive trophoblast appears to transcribe the same MHC class I loci transcribed in lymphocytes, including both polymorphic and nonpolymorphic loci. These data from the horse demonstrate that functional alloantigen presentation by trophoblast can be a normal part of early pregnancy.

A BAC contig of approximately 400 kb contains the classical class I major histocompatibility complex (MHC) genes of cattle

A cattle BAC library derived from an MHC homozygous animal was screened for MHC class I genes. This revealed at least nine class I-related genes in a contig spanning approximately 400 kb, and several additional genes on other clones. The three classical class I genes expressed on this haplotype (A14) were shown to be distributed over a region at most 212 kb apart.

Increased expression of major histocompatibility complex (MHC) class I transplantation antigens in bovine trophoblast cells before fusion with maternal cells

The mammalian fetus is potentially at risk from maternal immune attack because it can express paternally inherited polymorphic antigens, including those encoded by the major histocompatibility complex (MHC). The aim of this study was to investigate in more detail MHC class I upregulation by binucleate trophoblast cells in the bovine placenta. A method was developed to isolate binucleate cells by enzymatic disaggregation and density gradient centrifugation of bovine placental cotyledons. In cytospin preparations, 25-30% of purified binucleate cells stained positively with antibodies that recognize bovine MHC class I. The same antibodies were used to immunoprecipitate radiolabelled class I molecules from lysates of binucleate cells and fetal peripheral blood mononuclear cells. The protein species isolated from the two types of cell were similar in size and degree of glycosylation. PCR amplification of cDNA generated from binucleate cells and subsequent sequence analysis demonstrated transcription of MHC class I mRNA species similar to those found in fetal peripheral blood mononuclear cells, and there was no evidence of genetic imprinting of paternally inherited alleles. These results indicate that binucleate cells upregulate expression of MHC class I as they differentiate from MHC-negative uninucleate trophoblast cells. This finding has important implications for the immunological status of the fetus, as binucleate trophoblast cells are destined to cross to the maternal side of the placenta where they fuse with maternal cells. The immunological function of the resulting antigenically mixed fetomaternal hybrid minisyncytia is unknown.

Molecular and functional characterization of genes encoding horse MHC class I antigens

Sequence and functional analyses were undertaken on two cDNAs and a genomic clone encoding horse major histocompatibility complex (MHC) class I molecules. All of the clones were isolated from a single horse that is homozygous for all known horse MHC class I and class II antigens. The two cDNAs (clones 8-9 and 1-29) were isolated from a lymphocyte library and encode polymorphic MHC antigens from two loci. The genomic cosmid clone, isolated from a sperm library, contains the 8-9 gene. All three genes were expressed in mouse L-cells and were recognized by alloantisera and, for the cDNAs, by alloreactive cytotoxic T lymphocytes. A total of 3815 bp of the genomic clone were sequenced, extending from 429 bp upstream (5') of the leader peptide through the 3' untranslated region. Promoter region motifs and an intron-exon structure characteristic of MHC class I genes of other species were found. A subclone containing 407 bp of the promoter region was inserted into a chloramphenicol acetyl transferase reporter plasmid, tested in transient transfection assays, and found to have promoter activity in heterologous cells. This genomic clone will enable detailed studies of MHC class I gene regulation in horse trophoblasts, and in horse retroviral infections.

Increased expression of major histocompatibility complex (MHC) class I transplantation antigens in bovine trophoblast cells before fusion with maternal cells

The mammalian fetus is potentially at risk from maternal immune attack because it can express paternally inherited polymorphic antigens, including those encoded by the major histocompatibility complex (MHC). The aim of this study was to investigate in more detail MHC class I upregulation by binucleate trophoblast cells in the bovine placenta. A method was developed to isolate binucleate cells by enzymatic disaggregation and density gradient centrifugation of bovine placental cotyledons. In cytospin preparations, 25-30% of purified binucleate cells stained positively with antibodies that recognize bovine MHC class I. The same antibodies were used to immunoprecipitate radiolabelled class I molecules from lysates of binucleate cells and fetal peripheral blood mononuclear cells. The protein species isolated from the two types of cell were similar in size and degree of glycosylation. PCR amplification of cDNA generated from binucleate cells and subsequent sequence analysis demonstrated transcription of MHC class I mRNA species similar to those found in fetal peripheral blood mononuclear cells, and there was no evidence of genetic imprinting of paternally inherited alleles. These results indicate that binucleate cells upregulate expression of MHC class I as they differentiate from MHC-negative uninucleate trophoblast cells. This finding has important implications for the immunological status of the fetus, as binucleate trophoblast cells are destined to cross to the maternal side of the placenta where they fuse with maternal cells. The immunological function of the resulting antigenically mixed fetomaternal hybrid minisyncytia is unknown.

HLA-G suppresses proliferation of CD4(+) T-lymphocytes

HLA-G is a non-classical MHC class 1 molecule, expressed primarily on human foetal trophoblast cells, which exhibits almost no genetic polymorphism. Because of these unusual features, HLA-G has been suggested to help prevent maternal immune attack of the semi-allogeneic foetus. The aim of these experiments was to investigate the effects of HLA-G on T-lymphocyte responses by using MHC class II-bearing HLA-G transfectants as stimulators of a mixed lymphocyte reaction. The presence of HLA-G, but not classical HLA class I, on the surface of stimulator cells markedly suppressed thymidine incorporation by peripheral blood mononuclear responder cells from a class I-similar, class II-dissimilar male. The suppressive effect of HLA-G on the mixed lymphocyte reaction persisted after depletion of phagocytes and CD8(+) T-cells from the responder population, but the mixed lymphocyte reaction was entirely abolished by depletion of CD4(+) T-cells. These results suggest that HLA-G exerts a direct suppressive effect on CD4(+) T-lymphocytes, even in the absence of the CD8(+) cells with which other human MHC class I molecules are thought to interact. Thus, HLA-G may allow the foetus to escape maternal immune attack by modulating CD4(+) T-cell activity.

The short forms of HLA-G are unlikely to play a role in pregnancy because they are not expressed at the cell surface

HLA-G is a nonclassical class I MHC molecule of unknown function expressed on human invasive trophoblast. In trophoblast cells, HLA-G mRNA is alternatively spliced into a variety of forms which are predicted to encode a full length membrane-bound form, three short membrane-bound isoforms and two soluble isoforms. The aim of this study was to determine which of these protein isoforms are translated, which are expressed on the cell surface and which are secreted. Artificial cDNAs encoding the isoforms were generated by PCR mutagenesis, ligated to an epitope tag and transfected into a human cell line capable of expressing MHC class I. Protein products of appropriate sizes were detected in cells transfected with cDNAs encoding all membrane-bound forms, but surface biotinylation studies indicated that only full length membrane-bound HLA-G was present at the cell surface. Full length HLA-G was also detected by surface antibody binding and flow cytometry. Soluble HLA-G1 was detected in cells transfected with the appropriate cDNA only after treatment with monensin, which inhibits transport of glycoproteins through the Golgi apparatus. These results suggest that full length HLA-G, but not short HLA-G isoforms can be expressed on the surface of human cells and that soluble HLA-G is rapidly secreted. Thus, it is likely that the full length membrane-bound and soluble forms of HLA-G are the only biologically active forms to which the mother is exposed.

Variation in the number of expressed MHC genes in different cattle class I haplotypes

Analysis of cattle major histocompatibility complex (MHC) (BoLA) class I gene expression using serological and biochemical methods has demonstrated a high level of polymorphism. However, analysis of class I cDNA sequences has failed to produce conclusive evidence concerning the number and nature of expressed genes. Such information is essential for detailed studies of cattle immune responses, and to increase our understanding of the mechanisms of MHC evolution. In this study a selective breeding programme has been used to generate a number of MHC homozygous cattle expressing common serologically defined class I specificities. Detailed analysis of five class I haplotypes was carried out, with transcribed class I genes identified and characterized by cDNA cloning, sequence analysis, and transfection/expression studies. Surface expression of the gene products (on lymphocytes) was confirmed using monoclonal antibodies of defined BoLA specificity. Phylogenetic analysis of available transcribed cattle MHC class I sequences revealed complex evolutionary relationships including possible evidence for recombination. The study of individual haplotypes suggests that certain groupings of related sequences may correlate with loci, but overall it was not possible to define the origin of individual alleles using this approach. The most striking finding of this study is that none of the cattle class I genes is consistently expressed, and that in contrast to human, haplotypes differ from one another in both the number and composition of expressed classical class I genes.

Evolutionary history of MHC class I genes in the mammalian order Perissodactyla

We carried out an analysis of partial sequences from expressed major histocompatibility complex (MHC) class I genes isolated from a range of equid species and more distantly related members of the mammalian order Perissodactyla. Phylogenetic analysis revealed a minimum of six groups, five of which contained genes and alleles that are found in equid species and one group specific to the rhinoceros. Four of the groups contained only one, or very few sequences, indicating the presence of relatively nonpolymorphic loci, while another group contained the majority of the equid sequences identified. These data suggest that a diversification of MHC genes took place after the split between the Equidae and the Rhinocerotidae yet before the speciation events within the genus Equus.

Standardisation of a procedure for quantifying surface antigens by indirect immunofluorescence

Quantitative indirect immunofluorescence (QIIF) methods used to measure absolute numbers of surface-expressed antigens have produced conflicting results [Marchant, A., Duchow, J., Delville, J., Goldman, M., 1992. Lipopolysaccharide induces up-regulation of CD14 molecule on monocytes in human whole blood. European Journal of Immunology 22, 1663-1665; Antal-Szalmas, P., van Strijp, J.A.G., Weersink, A.J.L., Verhoef, J., van Kessel, K.P.M., 1997. Quantitation of surface CD14 on human monocytes and neutrophils. Journal of Leukocyte Biology 61, 721-728.]. The aim of this study was to standardise a flow cytometric method using the quantitative indirect immunofluorescence kit (QIFIkit, Dako, Denmark) for quantifying surface-expressed bovine classical major histocompatibility complex (MHC) class I molecules. The importance of accurately titrating antibodies in this procedure and using live cell gates is already accepted. However, little work has been carried out in optimising cell washes to remove excess antibody, or to study the influence of cell numbers used in the assay. In addition, information on the binding properties of each antibody is required in order to make accurate measurements. This study demonstrates that a number of critical parameters must be established prior to using this method for accurate numerical assessment of cell surface-expressed molecules.

Little evidence of HLA-G mRNA polymorphism in Caucasian or Afro-Caribbean populations

HLA-G is a nonclassical class I MHC molecule of unknown function expressed on human trophoblast. The level of polymorphism at the HLA-G locus is of considerable importance, since the paternally inherited gene product is exposed to the maternal immune system during pregnancy. However, previous studies of HLA-G polymorphism using genomic DNA samples have produced conflicting results. Our aim was to investigate polymorphism in trophoblast HLA-G mRNA from pregnancies in ten Caucasian and twelve Afro-Caribbean women by RT-PCR. A similar PCR protocol was also applied to umbilical cord blood genomic DNA from two Caucasian and two Afro-Caribbean neonates. Caucasian cDNA yielded only two different sequences: G*01011, and one containing a previously reported synonymous substitution. Afro-Caribbean samples yielded these sequences as well as one previously reported conservative (leucine-to-isoleucine) substitution. PCR amplification from genomic DNA samples from both populations using previously published primer pairs generated sequences containing multiple substitutions, many of which were nonsynonymous. More than two sequences were produced from genomic DNA from each individual. In contrast, amplification from the same genomic DNA using new primers complementary to exons of the HLA-G gene yielded the same few sequences generated from cDNA. These results suggest that polymorphism at the HLA-G locus is extremely limited in Caucasian and Afro-Caribbean populations. This suggests that spurious polymorphism has been reported in African Americans due to the use of intron-complementary PCR primers on genomic DNA samples. The monomorphic nature of HLA-G may allow trophoblast to carry out the immunological functions of class I-bearing tissues without compromising successful pregnancy.

Tetrameric complexes of human histocompatibility leukocyte antigen (HLA)-G bind to peripheral blood myelomonocytic cells

The nonclassical MHC class I molecule human histocompatibility leukocyte antigen (HLA)-G is selectively expressed on fetal trophoblast tissue at the maternal-fetal interface in pregnancy. It has long been suggested that HLA-G may inhibit maternal natural killer (NK) cells through interaction with particular NK cell receptors (KIRs). To investigate interactions of HLA-G, we constructed phycoerythrin-labeled tetrameric complexes of HLA-G refolded with a self-peptide. These HLA-G tetramers failed to bind to NK cells and cells transfected with CD94/NKG2 and killer immunoglobulin-like NK receptors. In contrast, HLA-G tetramers did bind to peripheral blood monocytes, staining a CD16(+)CD14(mid) subset with greater intensity. On transfectants, HLA-G tetramers bound to inhibitory immunoglobulin-like transcript (ILT)2 and ILT4 receptors. However, staining in the presence of antibodies reactive with ILT receptors revealed that the interaction of HLA-G tetramers with blood monocytes was largely due to binding to ILT4. These results suggest that the primary role of HLA-G may be the modulation of myelomonocytic cell behavior in pregnancy.

Cattle MHC: evolution in action?

Because major histocompatibility complex (MHC) genes play a major role in the development of acquired immune responses, it is essential to obtain comparative information on their organisation, expression and possible functional dichotomies in different species. In human, three classical, polymorphic class I genes (HLA-A, B- and -C) and four expressed A/B class II gene pairs (HLA-DM, -DP, -DQ and -DR) are each present on all haplotypes. With the exception of the HLA-DRB loci, it has been assumed that a similar rigid organisational situation exists in other mammalian species. However, extensive analysis of the bovine MHC (BoLA) at both the genomic and transcriptional levels has revealed a degree of genetic fluidity not described in other species. None of the four (or more) classical class I genes identified is consistently expressed, and haplotypes differ from one another in both the number and composition of expressed class I genes. Similarly, in the class II region, the number of DQ genes varies between haplotypes in both number and composition. These variations in both class I and II (which appear to reflect differences at the genomic level) are likely to play an important role in cattle immune responses. The observed phenotypic differences in cattle demonstrate very clearly the dynamic nature of the MHC region. This review addresses the functional impact of such variation in different breeds and populations, and its significance in terms of MHC evolution.

Contribution of advances in immunology to vaccine development

During the last 10 years, investigation of the bovine immune system has generated knowledge and reagents that can now be applied to study the mechanisms of immunity to disease and the identity of antigens recognized by protective immune responses. Such studies can indicate which antigens are likely to be effective in subunit vaccines and also highlight the type of antigen delivery system that will be required for a vaccine to induce a protective immune response. In the case of bovine RSV, studies of immune responses in the target host have demonstrated that both antibody and CTL responses play an important role in immunity. Both the F and G glycoproteins have been identified as targets of protective antibodies, and systems have been established that will allow the identification of the viral antigens recognized by CTL. Further studies of CD4+ T-cell responses to the virus are required to determine whether or not components of the response have the potential to enhance disease and, therefore, need to be avoided in vaccination strategies.

DNA typing for BoLA class I using sequence-specific primers (PCR-SSP)

The analysis of cattle MHC (BoLA) class I gene expression is an essential component of studies on immune responses and susceptibility to disease. International BoLA workshops have generated data and reagents that allow discrimination of class I molecules at the haplotype level, but progress has been limited by difficulties encountered in defining single alleles. Our aim in this study was to develop a DNA-based system for improved identification of expressed class I alleles, utilizing available cDNA sequences derived from cattle carrying a series of serologically defined class I specificities. This method has allowed more accurate typing of animals for expression of the class I genes present within a small number of haplotypes. The method has also reliably differentiated between allelic variants (identified by prior sequence analysis) and has split existing serological specificities. The data show that MHC class I genes in cattle are more polymorphic than demonstrated by serology and biochemical analysis.

Regulation of MHC class I gene expression is at transcriptional and post-transcriptional level in bovine placenta

A previous study of MHC in cattle trophoblast demonstrated low or absent class I expression, using a broad specificity monoclonal antibody. The study reported here uses MHC-defined cattle and embryo transfer to ensure MHC incompatibility between dam and calf. Transcription and expression of defined class I genes was examined in placentomes taken at term, using monoclonal antibodies to bovine class I, a gene-specific DNA-based typing system, and in situ hybridisation. Results demonstrate intermediate levels of fetal MHC class I mRNA in trophoblast, but no detectable fetal class I protein. This suggests a level of transcriptional down-regulation, and a post-transcriptional block which might involve other gene products, such as beta2-microglobulin (beta 2m), or proteins involved in generation/transport of peptides.

Identification of potential CTL epitopes of bovine RSV using allele-specific peptide motifs from bovine MHC class I molecules

Respiratory syncytial virus (RSV) is a major cause of lower respiratory tract infection in young infants and housed calves. Depletion of CD8+ lymphocytes from calves inhibited their ability to clear the virus from the nasopharynx and lungs. To study these cells further, a cytotoxic T lymphocyte (CTL) assay was established. CTL could be demonstrated in the peripheral blood of gnotobiotic calves 7-10 days post infection (p.i.) with RSV and in lungs 10 days p.i. This response was both MHC-restricted and virus-specific. Following separation of the lung lymphocytes by magnetic activated cell sorting, it was shown that the cytolytic activity was mediated by cells of the CD8+ phenotype. To identify epitopes recognised by bovine CTL, the consensus motifs from MHC class I alleles found in the herd at Compton were identified. cDNA libraries were constructed and screened for full length class I sequences. The isolated cDNA clones were then transfected into mouse P815 cells and the expressed product immunoprecipitated and matched with a serological specificity. The bovine MHC class I molecules were isolated from lysed transfected cells by affinity chromatography, using a monoclonal antibody specific for bovine MHC class I, and bound peptides were separated by reverse-phase HPLC. Analysis of the protein sequences of bovine RSV for the defined motifs has identified potential CTL epitopes.

At least four MHC class I genes are transcribed in the horse: phylogenetic analysis suggests an unusual evolutionary history for the MHC in this species

Nineteen horse MHC class I specificities have been serologically identified previously at a single locus (ELA-A), and two other specificities appear to be coded at other loci. Biochemical studies indicate that there are at least two expressed loci. In order to establish the number of transcribed horse MHC class I genes, we made a cDNA library from a heterozygous animal (ELA-A3/A7), and screened for positive clones using a bovine class I probe. More than 200 class I clones were isolated in this way, and so far seven unique full length sequences have been identified. All of the sequences are predicted to code for surface expressed, functional molecules. The number of different sequences identified demonstrate that at least four genes are transcribed, although variations in transmembrane length (which is generally conserved in class I loci) suggest that five genes could be represented. Evolutionary analysis of these sequences (and two additional sequences known to represent different horse class I loci) reveals no firm relationships, such that the division between the different loci cannot be discerned. These results suggest an unusual evolutionary history for the horse MHC, the precise nature of which may be revealed only following further cross-species comparisons.

Methylation status and transcriptional expression of the MHC class I loci in human trophoblast cells from term placenta

Of the various molecular regulatory mechanisms that may be used by human trophoblast cells to down-regulate expression of HLA class I genes, we chose to investigate the methylation of DNA, generally associated with inhibition of transcription. We analyzed the methylation status of different HLA class I loci in villous and extravillous cytotrophoblast cells and in vitro-differentiated syncytiotrophoblast, purified from human term placenta, as well as in the human trophoblast-derived JAR and JEG-3 cell lines. We then compared methylation status and transcriptional activity. An inverse relationship was established between JAR and JEG-3: HLA-A, -B, and -G are methylated and repressed in JAR, whereas in JEG-3, HLA-A is methylated and repressed but HLA-B and -G are partially methylated and transcribed. HLA-E is unmethylated and transcribed in both cell lines. Apart from HLA-E, which is always unmethylated and transcribed, no such relationship exists for the other class I loci in trophoblast cells. Whereas nonclassical HLA-G and classical HLA-A and -B class I genes are undermethylated in both cytotrophoblast and syncytiotrophoblast, they are clearly transcribed in the former but minimally transcribed in the latter subpopulation. Thus, the down-regulation of class I gene expression in the in vitro-differentiated syncytiotrophoblast is unlikely to be caused by DNA methylation. Furthermore, there is no detectable expression of any class I molecule at the cell surface of either trophoblast cell subpopulation, suggesting a negative control on translation and/or on the secretory pathway to the plasma membrane.

Methylation status and transcriptional expression of the MHC class I loci in human trophoblast cells from term placenta

Of the various molecular regulatory mechanisms that may be used by human trophoblast cells to down-regulate expression of HLA class I genes, we chose to investigate the methylation of DNA, generally associated with inhibition of transcription. We analyzed the methylation status of different HLA class I loci in villous and extravillous cytotrophoblast cells and in vitro-differentiated syncytiotrophoblast, purified from human term placenta, as well as in the human trophoblast-derived JAR and JEG-3 cell lines. We then compared methylation status and transcriptional activity. An inverse relationship was established between JAR and JEG-3: HLA-A, -B, and -G are methylated and repressed in JAR, whereas in JEG-3, HLA-A is methylated and repressed but HLA-B and -G are partially methylated and transcribed. HLA-E is unmethylated and transcribed in both cell lines. Apart from HLA-E, which is always unmethylated and transcribed, no such relationship exists for the other class I loci in trophoblast cells. Whereas nonclassical HLA-G and classical HLA-A and -B class I genes are undermethylated in both cytotrophoblast and syncytiotrophoblast, they are clearly transcribed in the former but minimally transcribed in the latter subpopulation. Thus, the down-regulation of class I gene expression in the in vitro-differentiated syncytiotrophoblast is unlikely to be caused by DNA methylation. Furthermore, there is no detectable expression of any class I molecule at the cell surface of either trophoblast cell subpopulation, suggesting a negative control on translation and/or on the secretory pathway to the plasma membrane.

Transmembrane and cytoplasmic domain sequences demonstrate at least two expressed bovine MHC class I loci

We have used the polymerase chain reaction to amplify cDNA from expressed bovine major histocompatibility complex class I genes. Sequences obtained from transmembrane and cytoplasmic domains were used to identify the number of expressed alleles. Data from three animals suggest that there are four major expressed alleles, representing the products of two (or more) loci. We have also demonstrated the presence of an alternatively spliced mRNA, which has been observed in five animals. The alternative splicing removes exon 7 (the major site of class I phosphorylation), which predicts a truncated molecule with a cytoplasmic portion 16 amino acids shorter than usual. This phenomenon was detected for only a single class I allele within each individual.

Human trophoblast and the choriocarcinoma cell line BeWo express a truncated HLA Class I molecule

Extravillous trophoblast from normal human placenta has been shown previously to express an unusual form of HLA class I molecule, as does a choriocarcinoma cell line, BeWo. This molecule has a H chain of approximately 40 kDa and appears to be nonpolymorphic. We have isolated and sequenced a HLA class I cDNA clone, which probably corresponds to this molecule, from a library derived from BeWo. The nucleotide sequence shows a high degree of homology with the published sequence of a genomic clone, HLA 6.0, which is the product of a class I locus other than A, B, or C, (provisionally designated "HLA G"). The expressed product of this locus has not previously been localized. We have used the polymerase chain reaction to demonstrate the presence of similar HLA class I sequences in cDNA from normal extravillous trophoblast. Although there is some nucleotide sequence polymorphism the amino acid sequence of this molecule is conserved. It is therefore unlikely to provoke immune responses even though it is found at the fetal-maternal interface.

Human trophoblast and the choriocarcinoma cell line BeWo express a truncated HLA Class I molecule

Extravillous trophoblast from normal human placenta has been shown previously to express an unusual form of HLA class I molecule, as does a choriocarcinoma cell line, BeWo. This molecule has a H chain of approximately 40 kDa and appears to be nonpolymorphic. We have isolated and sequenced a HLA class I cDNA clone, which probably corresponds to this molecule, from a library derived from BeWo. The nucleotide sequence shows a high degree of homology with the published sequence of a genomic clone, HLA 6.0, which is the product of a class I locus other than A, B, or C, (provisionally designated "HLA G"). The expressed product of this locus has not previously been localized. We have used the polymerase chain reaction to demonstrate the presence of similar HLA class I sequences in cDNA from normal extravillous trophoblast. Although there is some nucleotide sequence polymorphism the amino acid sequence of this molecule is conserved. It is therefore unlikely to provoke immune responses even though it is found at the fetal-maternal interface.

Structural homologies between two HLA B27-restricted peptides suggest residues important for interaction with HLA B27

Recently we described an HLA B27-restricted peptide derived from HIV gag p24 protein. In this study we have isolated an HLA B27-restricted peptide from the nucleoprotein (NP) of influenza A virus. The shortest fragment recognized by cytotoxic T lymphocyte (CTL) is eight amino acids long, residues 384-391. Comparison of the sequence of these two HLA B27 restricted peptides reveals homologies which can be aligned from one peptide to the other. Of the eight residues, two are identical: tryptophan and isoleucine. Both peptides have a positively charged residue at the N terminus, lysine at position 265 of gag and arginine at position 384 of NP. Using modified peptides we have shown that lysine or arginine is crucial for the interaction with HLA B27. The wild-type gag peptide blocked CTL recognition of NP peptide by influenza-specific CTL, but removal of the lysine prevented inhibition of NP peptide recognition. The importance of these charged residues was confirmed by the observation that truncated NP and gag peptides where the lysine or arginine was removed were not recognized by specific CTL. Further studies showed that the tryptophan residue influenced the association of the gag peptide with HLA B27, because the affinity of the gag peptide for B27 was strongly increased after replacing this residue with a leucine or a tyrosine. However, these peptides were not recognized by gag-specific CTL, suggesting that the tryptophan may interact with both HLA B27 and T cell receptor. These observations should help in the identification of HLA B27-restricted peptides from other viruses or organisms.

Complete nucleotide sequence of a unique HLA class I C locus product expressed on the human choriocarcinoma cell line BeWo

We have used Northern blot analysis to detect mRNA from class I HLA genes in the human choriocarcinoma cell line BeWo, which has been previously shown to express an atypical HLA class I molecule, in the absence of HLA A and B. Hybridization was seen with three class I DNA probes, the strongest being seen with the probe pC800, which corresponds to an 800-bp section of the Cw3 gene. We have made cDNA libraries from BeWo cells and screened for positive clones by using class I DNA probes. Of the clones isolated, we determined the complete sequence of one and partial sequence of five shorter clones. They all code for an identical C locus-related product, which does not correspond to published C locus sequences.

Complete nucleotide sequence of a unique HLA class I C locus product expressed on the human choriocarcinoma cell line BeWo

We have used Northern blot analysis to detect mRNA from class I HLA genes in the human choriocarcinoma cell line BeWo, which has been previously shown to express an atypical HLA class I molecule, in the absence of HLA A and B. Hybridization was seen with three class I DNA probes, the strongest being seen with the probe pC800, which corresponds to an 800-bp section of the Cw3 gene. We have made cDNA libraries from BeWo cells and screened for positive clones by using class I DNA probes. Of the clones isolated, we determined the complete sequence of one and partial sequence of five shorter clones. They all code for an identical C locus-related product, which does not correspond to published C locus sequences.