H-Y antigens

Fetal-origin cells in maternal circulation correlate with placental dysfunction, fetal sex, and severe hypertension during pregnancy

Fetal microchimerism (FMc) arises when fetal cells enter maternal circulation, potentially persisting for decades. Increased FMc is associated with fetal growth restriction, preeclampsia, and anti-angiogenic shift in placenta-associated proteins in diabetic and normotensive term pregnancies. The two-stage model of preeclampsia postulates that placental dysfunction causes such shift in placental growth factor (PlGF) and soluble fms-like tyrosine kinase-1 (sFLt-1), triggering maternal vascular inflammation and endothelial dysfunction. We investigated whether anti-angiogenic shift, fetal sex, fetal growth restriction, and severe maternal hypertension correlate with FMc in hypertensive disorders of pregnancy with new-onset features (n = 125). Maternal blood was drawn pre-delivery at > 25 weeks' gestation. FMc was detected by quantitative polymerase chain reaction targeting paternally inherited unique fetal alleles. PlGF and sFlt-1 were measured by immunoassay. We estimated odds ratios (ORs) by logistic regression and detection rate ratios (DRRs) by negative binomial regression. PlGF correlated negatively with FMc quantity (DRR = 0.2, p = 0.005) and female fetal sex correlated positively with FMc prevalence (OR = 5.0, p < 0.001) and quantity (DRR = 4.5, p < 0.001). Fetal growth restriction no longer correlated with increased FMc quantity after adjustment for correlates of placental dysfunction (DRR = 1.5, p = 0.272), whereas severe hypertension remained correlated with both FMc measures (OR = 5.5, p = 0.006; DRR = 6.3, p = 0.001). Our findings suggest that increased FMc is independently associated with both stages of the two-stage preeclampsia model. The association with female fetal sex has implications for microchimerism detection methodology. Future studies should target both male and female-origin FMc and focus on clarifying which placental mechanisms impact fetal cell transfer and how FMc impacts the maternal vasculature.

Effects of biological sex mismatch on neural progenitor cell transplantation for spinal cord injury in mice

Despite advancement of neural progenitor cell transplantation to spinal cord injury clinical trials, there remains a lack of understanding of how biological sex of transplanted cells influences outcomes after transplantation. To address this, we transplanted GFP-expressing sex-matched, sex-mismatched, or mixed donor cells into sites of spinal cord injury in adult male and female mice. Biological sex of the donor cells does not influence graft neuron density, glial differentiation, formation of the reactive glial cell border, or graft axon outgrowth. However, male grafts in female hosts feature extensive hypervascularization accompanied by increased vascular diameter and perivascular cell density. We show greater T-cell infiltration within male-to-female grafts than other graft types. Together, these findings indicate a biological sex-specific immune response of female mice to male donor cells. Our work suggests that biological sex should be considered in the design of future clinical trials for cell transplantation in human injury.

In this study, Pitonak et al. report that transplantation of neural progenitor cells derived from male donors trigger an immune rejection response following transplantation into sites of spinal cord injury in female mice.

Characteristics of preeclampsia in donor cell gestations

Pregnancies conceived through donor oocytes or sperm show increased risk for preeclampsia. We studied this issue in a preeclampsia case-control cohort (n = 2778), and found overrepresentation of donor cell gestations among women with preeclampsia (14/1627, 0.86%; OR 1.81; 95% CI: 1.07-3.08; P = 0.025) compared to the population data. Moreover, we observed excess of male births from donor cell pregnancies (male-to-female ratio 2.5 vs. 0.97; OR 2.57; 95% CI 1.02-6.36; P = 0.043). Maternal age (36.7 vs. 30.2; P < 0.0001) and preterm deliveries (64% vs. 38%; P = 0.046) distinguished donor cell gestations from other pregnancies with preeclampsia. These results support foreign fetal antigens as modulators of preeclampsia.

Fetal HLA-G mediated immune tolerance and interferon response in preeclampsia

BACKGROUND

Fetal immune tolerance is crucial for pregnancy success. We studied the link between preeclampsia, a severe pregnancy disorder with uncertain pathogenesis, and fetal human leukocyte antigen G (HLA-G) and other genes regulating maternal immune responses.

METHODS

We assessed sex ratios and regulatory HLA-G haplotypes in population cohorts and series of preeclampsia and stillbirth. We studied placental mRNA expression of 136 genes by sequencing and HLA-G and interferon alpha (IFNα) protein expression by immunohistochemistry.

FINDINGS

We found underrepresentation of males in preeclamptic births, especially those delivered preterm or small for gestational age. Balancing selection at HLA-G associated with the sex ratio, stillbirth, and preeclampsia. We observed downregulation of HLA-G, its receptors, and many other tolerogenic genes, and marked upregulation of IFNA1 in preeclamptic placentas.

INTERPRETATION

These findings indicate that an evolutionary trade-off between immune tolerance and protection against infections at the maternal-fetal interface promotes genetic diversity in fetal HLA-G, thereby affecting survival, preeclampsia, and sex ratio. We highlight IFNA1 as a potential mediator of preeclampsia and a target for therapeutic trials.

FUNDING

Finnish Medical Foundation, Päivikki and Sakari Sohlberg Foundation, Karolinska Institutet Research Foundation, Scandinavia-Japan Sasakawa Foundation, Japan Eye Bank Association, Astellas Foundation for Research on Metabolic Disorders, Japan Society for the Promotion of Science, Knut and Alice Wallenberg Foundation, Swedish Research Council, Medical Society Liv och Hälsa, Sigrid Jusélius Foundation, Helsinki University Hospital and University of Helsinki, Jane and Aatos Erkko Foundation, Academy of Finland, Finska Läkaresällskapet, Novo Nordisk Foundation, Finnish Foundation for Pediatric Research, and Emil Aaltonen Foundation.

Applying real-time quantitative PCR to diagnosis of freemartin in Holstein cattle by quantifying SRY gene: a comparison experiment

BACKGROUND

Freemartinism generally occurs in female offspring of dizygotic twins in a mixed-sex pregnancy. Most bovine heterosexual twin females are freemartins. However, about 10% of bovine heterosexual twin females are fertile. Farmers mostly cull bovine fertile heterosexual twin females due to the lack of a practical diagnostic approach. Culling of such animals results in economic and genetic-material losses both for dairy and beef industry.

METHODS

In this study, a comparative test, including qualitative detection of SRY gene by polymerase chain reaction (PCR), quantitative detection of relative content of SRY by real-time quantitative polymerase chain reaction (qPCR), and quantitative detection of H-Y antigen, was performed to establish the most accurate diagnosis for freemartin. Twelve Holstein heterosexual twin females were used in this study, while three normal Holstein bulls and three normal Holstein cows were used as a positive and negative control, respectively.

RESULTS

Polymerase chain reaction results revealed that SRY gene were absent in three heterosexual twin females and only two of them were verified as fertile in later age. The qPCR results showed that relative content of SRY was more than 14.2% in freemartins and below 0.41% in fertile heterosexual twin females. The H-Y antigen test showed no significant numerical difference between freemartin and fertile heterosexual twin female.

DISCUSSION

Our results show that relative content of SRY quantified by qPCR is a better detection method for diagnosis of freemartin in Holstein cattle as compare to qualitative detection of SRY gene by PCR or quantitative detection of H-Y antigen. To the authors' knowledge, this is the first time we applied qPCR to diagnosing freemartin by quantifying SRY gene and got relative SRY content of each freemartin and fertile heterosexual twin female. We concluded that low-level of SRY would not influence fertility of bovine heterosexual twin female.

Facets of Clinical Appearance and Aetiology in an Unusual Bovine Amorphus Globosus

Amorphus globosus is a rare entity, more common in the cow but also reported in mares, buffaloes and goats. In respect of both development and clinical presentation, this abnormity can be evolved very variably. Previously, it has been discussed whether it is a form of twin pregnancy or placental teratoma. This case report deals with morphology and genetic observations in an unusual bovine amorphus globosus exhibiting a rudimentary clitoris and vulva, gut-like structures and rudimentary bones. The amorphus globosus was shown to be dizygotic to the normal male twin using the BovineSNP50 v2 BeadChip and had a genetical female sex. Aspects of aetiology and pathogenesis as well as the possible impact of amorphus globosus in the emergence of freemartinism are discussed.

How Do CD4(+) T Cells Detect and Eliminate Tumor Cells That Either Lack or Express MHC Class II Molecules?

CD4⁺ T cells contribute to tumor eradication, even in the absence of CD8⁺ T cells. Cytotoxic CD4⁺ T cells can directly kill MHC class II positive tumor cells. More surprisingly, CD4⁺ T cells can indirectly eliminate tumor cells that lack MHC class II expression. Here, we review the mechanisms of direct and indirect CD4⁺ T cell-mediated elimination of tumor cells. An emphasis is put on T cell receptor (TCR) transgenic models, where anti-tumor responses of naïve CD4⁺ T cells of defined specificity can be tracked. Some generalizations can tentatively be made. For both MHCII^POS and MHCII^NEG tumors, presentation of tumor-specific antigen by host antigen-presenting cells (APCs) appears to be required for CD4⁺ T cell priming. This has been extensively studied in a myeloma model (MOPC315), where host APCs in tumor-draining lymph nodes are primed with secreted tumor antigen. Upon antigen recognition, naïve CD4⁺ T cells differentiate into Th1 cells and migrate to the tumor. At the tumor site, the mechanisms for elimination of MHCII^POS and MHCII^NEG tumor cells differ. In a TCR-transgenic B16 melanoma model, MHCII^POS melanoma cells are directly killed by cytotoxic CD4⁺ T cells in a perforin/granzyme B-dependent manner. By contrast, MHCII^NEG myeloma cells are killed by IFN-γ stimulated M1-like macrophages. In summary, while the priming phase of CD4⁺ T cells appears similar for MHCII^POS and MHCII^NEG tumors, the killing mechanisms are different. Unresolved issues and directions for future research are addressed.

Engineering the male-specificity of Fab against SDM antigen by chain shuffling

High-titer serologically detected male (SDM) antibody fragments are essential for specific binding to the SDM antigen and promoting its application. The A8 clone previously obtained from an original phage antibody library was further affinity-matured by light- and high-chain shuffling respectively, to generate the end product B9 clone. The binding capacity of B9 phage Fabs to male splenocytes doubled the value of its parental A8 clone (determined using ELISA). Based on immunofluorescent staining, B9-Fabs mainly bound to the surface antigen of male splenocytes and recognized testicular cells. The resulting B9-Fabs detected a single protein (approximately 40 kDa determined using Western blot analysis of male splenocytes and testis); its high SDM antigen binding ability might have been because of mutation sites and varied lengths of the amino acid sequences in the complementarity determining regions-3 of the κ and Fd chains. The new recombinant clones of Fab that were phage-enhanced using chain shuffling were candidate molecules for investigating molecular mechanisms of SDM antigens specific binding and applications.

Prenatal Influences on Sexual Orientation: Digit Ratio (2D:4D) and Number of Older Siblings

Prenatal androgen levels are suggested to influence sexual orientation in both sexes. The 2D:4D digit ratio has been found to associate with sexual orientation, but published findings have often been contradictory, which may partly be due to the large ethnic diversity between and within studied populations. In men, number of older brothers has been found to correlate positively with homosexuality. This phenomenon has been explained with a maternal immune reaction, which is provoked only by male fetuses and which gets stronger after each pregnancy. Here we assessed the relationship of sexual orientation to 2D:4D ratios and number of older siblings in Finland, where the population is found to be genetically relatively homogeneous. As in many previous studies, heterosexual men had lower 2D:4D than non-heterosexual men, which supports the notion that non-heterosexual men experience higher androgen levels in utero than population norms. Contrary to previous reports, non-heterosexual women had higher 2D:4D than heterosexual women. Non-heterosexual men had more older brothers and older sisters than heterosexual men. The greater number of older sisters in non-heterosexual men indicates that there are other factors that contribute to the higher birth order of homosexual men than the maternal immunization.

Construction and characterization of phage display library: Recognition of mouse serologically detected male (SDM) antigen

Improvement of animal embryo sexing depends upon high-titer serologically detected male (SDM) antibody fragments. SDM sera collected from isogenic C57BL/7 female mice after inoculation with male spleen cells were characterized and used for construction of a recombinant Fab antibody library against SDM antigen, and used for analysis of the binding capacity and specificity to SDM antigen. The heavy-chain Fd and full-length light-chain kappa were amplified by RT-PCR from a mouse (#6) that'ed high-titer antiserum. The amplified product was inserted into the pComb3 vector followed by co-infections with the help phage VCSM 13 for construction of the phage library, which gave 1.5x10(7) colonies with the titer of 3.2x10(11) pfu/ml by a recombination rate of 80%. Sequence analysis of the PCR products of plasmid DNA of E5 clones showed that V(H) and V(kappa) had common characteristics shared by other known variable region of antibodies. The Fab antibody libraries against SDM antigen were enriched by three cycles of affinity enrichment with male spleen cells, and two cycles of non-specific absorption with female spleen cells. The ELISA results showed that 9 of 15 clones had binding capacity to the SDM antigen. This is the first report on a phage display library of SDM antigen. The mouse Fab antibody library could be used for identifying SDM antigen, and for the development of sex determination of early embryos in mammals.

Quantitative and theoretical analyses of the relation between older brothers and homosexuality in men

Meta-analysis of aggregate data from 14 samples representing 10,143 male subjects shows that homosexuality in human males is predicted by higher numbers of older brothers, but not by higher numbers of older sisters, younger brothers, or younger sisters. The relation between number of older brothers and sexual orientation holds only for males. This phenomenon has therefore been called the fraternal birth order effect. Research on birth order, birth weight, and sexual orientation suggests that the developmental pathway to homosexuality initiated by older brothers operates during prenatal life. Calculations assuming a causal relation between older brothers and sexual orientation have estimated the proportion of homosexual men who owe their sexual orientation to fraternal birth order at 15% in one study and 29% in another. The maternal immune hypothesis proposes that the fraternal birth order effect reflects the progressive immunization of some mothers to male-specific antigens by each succeeding male fetus and the increasing effects of such immunization on sexual differentiation of the brain in each succeeding male fetus. There are at least three possible mechanisms by which the mother's immune response could influence the fetus: the transfer of anti-male antibodies across the placenta from the maternal into the fetal compartment, the transfer of maternal cytokines across the placenta, and maternal immune reactions affecting the placenta itself. This hypothesis is consistent with recent studies showing that the quantity of fetal cells that enter the maternal circulation is greater than previously thought, and that the number of male-specific proteins encoded by Y-chromosome genes is greater than previously thought.

Fraternal birth order and birth weight in probably prehomosexual feminine boys

The purpose of this study was to confirm a previous finding that homosexual males with older brothers weigh less at birth than do heterosexual males with older brothers. The subjects comprised 250 feminine boys referred to a child psychiatry service because of extreme cross-gender wishes or behavior and assumed, on the basis of previous research, to be prehomosexual, plus 739 control boys and 261 control girls referred to the same service for reasons unrelated to sexual orientation or gender identity disorder and assumed, from base-rate probabilities, to be preheterosexual. The feminine boys with two or more older brothers weighed 385 g less at birth than did the control boys with two or more older brothers (P = 0.005). In contrast, the feminine and control boys with fewer than two older brothers did not differ in birth weight. This finding suggests that the mechanism by which older brothers increase the odds of homosexuality in later-born males operates prior to the individual's birth. We hypothesize that this mechanism may be immunologic, that antimale antibodies produced by human mothers in response to immunization by male fetuses could decrease the birth weight of subsequent male fetuses as well as increase their odds of homosexuality.

Antigen-specific modulation of an immune response by in vivo administration of soluble MHC class I tetramers

Soluble MHC/peptide tetramers that can directly bind the TCR allow the direct visualization and quantitation of Ag-specific T cells in vitro and in vivo. We used HY-D(b) tetramers to assess the numbers of HY-reactive CD8+ T cells in HYTCR-transgenic mice and in naive, wild-type C57BL/6 (B6) mice. As expected, tetramer staining showed the majority of T cells were male-specific CD8+ T cells in female HY-TCR mice. Staining of B6 mice showed a small population of male-specific CD8+ T cells in female mice. The effect of administration of soluble MHC class I tetramers on CD8+ T cell activation in vivo was unknown. Injection of HY-D(b) tetramer in vivo effectively primed female mice for a more rapid proliferative response to both HY peptide and male splenocytes. Furthermore, wild-type B6 female mice injected with a single dose of HY-D(b) tetramer rejected B6 male skin grafts more rapidly than female littermates treated with irrelevant tetramer. In contrast, multiple doses of HY-D(b) tetramer did not further decrease graft survival. Rather, female B6 mice injected with multiple doses of HY-D(b) tetramer rejected male skin grafts more slowly than mice primed with a single injection of tetramer or irradiated male spleen cells, suggesting clonal exhaustion or anergy. Our data highlight the ability of soluble MHC tetramers to identify scarce alloreactive T cell populations and the use of such tetramers to directly modulate an Ag-specific T cell response in vivo.

Fraternal birth order and the maternal immune hypothesis of male homosexuality

In men, sexual orientation correlates with an individual's number of older brothers, each additional older brother increasing the odds of homosexuality by approximately 33%. It has been hypothesized that this fraternal birth order effect reflects the progressive immunization of some mothers to Y-linked minor histocompatibility antigens (H-Y antigens) by each succeeding male fetus and the concomitantly increasing effects of such maternal immunization on the future sexual orientation of each succeeding male fetus. According to this hypothesis, anti-H-Y antibodies produced by the mother pass through the placental barrier to the fetus and affect aspects of sexual differentiation in the fetal brain. This explanation is consistent with a variety of evidence, including the apparent irrelevance of older sisters to the sexual orientation of later born males, the probable involvement of H-Y antigen in the development of sex-typical traits, and the detrimental effects of immunization of female mice to H-Y antigen on the reproductive performance of subsequent male offspring. The maternal immune hypothesis might also explain the recent finding that heterosexual males with older brothers weigh less at birth than heterosexual males with older sisters and homosexual males with older brothers weigh even less than heterosexual males with older brothers.

H-Y antigen expression patterns in human X- and Y-chromosome-bearing spermatozoa

PROBLEM

Restricted expression of H-Y antigen on Y-chromosome-bearing sperm has been reported in some species, although such preferential expression for H-Y antigen in human sperm has yet to be described. In this study, an immunomagnetic approach was used to characterize antigen expression patterns as a function of sex-chromosome content.

METHOD OF STUDY

Human sperm was treated with monoclonal immunoglobulin (Ig) M antibodies directed against H-Y antigen. This preparation then was incubated with sheep antimouse IgM antibody affixed to paramagnetic beads, which then were exposed to a magnetic field and sorted. X- and Y-chromosome frequencies in the two subgroups of sperm were assayed by multiprobe fluorescent in situ hybridization (FISH).

RESULTS

Sperm were immunomagnetically separated into two populations: a reactive group (presumably, H-Y Ag+); and a nonreactive group (presumably, H-Y Ag-). Triple-color FISH analysis of 1,600 spermatozoa (800 in each group) showed the antigen's expression to be somewhat more prevalent among Y-chromosome-bearing sperm (54.1%), but a large proportion of Y-chromosome-bearing sperm (49.0%) did not express this antigen. The difference was not significant (P = 0.43).

CONCLUSIONS

The expression of H-Y antigen has a slightly higher frequency in human sperm containing the Y-chromosome, but its expression among X-chromosome-bearing sperm also is considerable. Current immunologic techniques relying on this antigen are unlikely to effect the sex selection of human sperm.