Purified human early pregnancy factor from preimplantation embryo possesses immunosuppresive properties

Comparison of immune modulatory properties of human multipotent mesenchymal stromal cells derived from bone marrow and placenta

Multipotent mesenchymal stromal cells (MSC) can be isolated from many tissues, including bone marrow (BM) and placenta (PL). Human placenta can be obtained readily without invasive procedures. There may be differences, however, in differentiation capacity and immunomodulation by MSC isolated from BM or PL. The early pregnancy factor (heat shock protein 10; EPF/Hsp10) is a small protein that exhibits immunomodulatory properties. We compared BM- and PL-MSC, and assessed their efficacy for suppressing T-cell proliferation in vitro and the role of EPF/Hsp10 in this process. PL-MSC were collected from whole placenta after removal of the amniotic and chorionic membranes followed by serial enzymatic digestions. The PL-MSC were compared to BM-MSC, obtained from healthy donors. Differentiation capacity, cytokine secretion, expression and secretion of immunomodulatory molecules, immunophenotype and real time proliferation were assessed using cytokine arrays, ELISA assays, flow cytometry, immunohistochemical staining and western blotting. Whereas BM-MSC consisted of a homogeneous cell population with strong expression of mesenchymal markers, PL-MSC consisted of a mixed population of cells with variable CD73, CD90 and CD105 expression. PL-MSC exhibited a significantly greater proliferation rate than BM-MSC. The presence of both stem cells and more mature cells in the PL-MSC cultures resulted in decreased differentiation capacity and reduced efficacy of immune suppression in co-cultures with T-cells. Although robust intracellular expression of EPF/Hsp10 in both BM- and PL-MSC was observed, secretion of the protein in response to immune activating stimuli remained below detectable levels. Secretion of pro-inflammatory cytokines was significantly greater in BM-MSC than PL-MSC, whereas no difference was observed in the secretion of hematopoiesis supporting growth factors. Development of culture methods for isolation of pure populations of PL-MSC may improve the quality of the product and reproducibility of results.

Identification of heat shock protein 10 within the equine embryo, endometrium, and maternal peripheral blood mononuclear cells

Early pregnancy factor has been identified as a 10-kDa extracellular homolog of heat shock protein 10 (Hsp10). Hsp10 has been detected during early pregnancy in serum of mice, sheep, pigs, horses, cows, and humans by the rosette inhibition test. Hsp10 has also been associated with several neoplastic and autoimmune diseases. The goal of the present study was to determine if Hsp10 could be detected in the early equine embryo through the use of immunohistochemistry and quantitative real-time PCR. Additionally, analysis of systemically harvested peripheral blood mononuclear cells (PBMCs) from both pregnant and nonpregnant mares was evaluated to determine expression levels of HSP10. Embryos were collected from Quarter Horse mares by uterine lavage at either 8 or 25 days after ovulation. Collection and separation of PBMCs occurred on Day 8 for both pregnant and nonpregnant mares. Immunohistochemistry revealed cytoplasmic localization of HSP10 throughout the single layer of ectodermal cells forming the trophoblast in Day-8 embryos. Day-25 embryos demonstrated intense localization focally along the apical border of ectodermal cells forming the trophoblast layer of the developing chorion. There was no nuclear staining in either embryonic population. Quantitative real-time PCR detected the presence of mRNA for HSP10 in both 8- and 25-day equine embryos. Day-25 embryos exhibited an elevated degree of expression (P = 0.006) compared with the 8-day embryos for HSP10. Endometrial samples did not display any significant difference in degree of expression for HSP10 (P = 0.10). Finally, PBMCs from pregnant mares demonstrated elevated (P = 0.03) expression of HSP10 compared to the nonpregnant mares on Day 8 of the estrous cycle. This study confirmed the presence of HSP10 protein and mRNA expression of HSP10 in equine embryos at two maturation stages. Additionally, the presence of increased gene expression within PBMCs of pregnant mares suggests communication, possibly leading to necessary immunomodulatory effects between the embryo and mare.

Copper-T intrauterine device and levonorgestrel intrauterine system: biological bases of their mechanism of action

All intrauterine devices (IUDs) that have been tested experimentally or clinically induce a local inflammatory reaction of the endometrium whose cellular and humoral components are expressed in the tissue and the fluid filling the uterine cavity. Depending on the reproductive strategy of the species considered and the anatomical features and physiologic mechanisms that characterize their reproductive system, the secondary consequences of this foreign body reaction can be very localized within the uterus, as in the rabbit, or widespread throughout the entire genital tract as in women or even systemic as in some farm animals. Levonorgestrel released from an IUD causes some systemic effects, but local effects such as glandular atrophy and stromal decidualization, in addition to the foreign body reaction, are dominant. Copper ions released from an IUD enhance the inflammatory response and reach concentrations in the luminal fluids of the genital tract that are toxic for spermatozoa. In the human, the entire genital tract appears affected due to luminal transmission of the noxa that accumulates in the uterine lumen. This affects the function and viability of gametes, decreasing the rate of fertilization and lowering the chances of survival of any embryo that may be formed, before it reaches the uterus. The bulk of the data indicate that if any embryos are formed in the chronic presence of an IUD, it happens at a much lower rate than in non-IUD users. The common belief that the usual mechanism of action of IUDs in women is destruction of embryos in the uterus is not supported by empirical evidence.

Early pregnancy factor: an extracellular chaperonin 10 homologue

Early pregnancy factor (EPF) has been identified as a homologue of chaperonin 10 (cpn10) with immunosuppressive and growth factor properties. As a homologue of cpn10, it belongs to the heat shock family of proteins (hsp) but, unlike other members of this family, EPF is detected extracellularly. Early pregnancy factor was first discovered in pregnancy serum by the rosette inhibition test, and the novelty of its discovery was that its presence could diagnose pregnancy within 6-24 h of a fertile mating. As well as being a monitor of the presence of a viable embryo, it is necessary for embryonic survival. In this capacity it acts as both an immunosuppressant and growth factor. Early pregnancy factor is also a product of proliferating primary and neoplastic cells and functions as an autocrine growth factor both in vivo and in vitro. It has a modifying effect on the outcome of experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis. Early pregnancy factor is considered to be one of the major factors involved in the modification of multiple sclerosis observed during pregnancy.

Supplementation effect of early pregnancy factor-positive serum into bovine in vitro fertilization culture medium

PROBLEM

Early pregnancy factor (EPF) has been detected in pregnant bovine serum, and its activity appeared from 24 to 48 hr after insemination. However, in bovine in vitro fertilization (IVF), an EPF-like substance(s) had been detected in the culture medium of fertilized ovum. Therefore, we think that EPF and EPF-like substance(s) are very important materials for the development of the embryo. In this study, we examined the development of the embryo when fertilized bovine ova were cultured with IVF culture medium supplemented with EPF-positive or -negative serum.

METHOD OF STUDY

EPF activity of each serum (fetal calf serum [FCS], calf serum [CS], estrus bovine serum, and pregnant bovine serum) was assessed by the bovine-rosette inhibition test. The sera were supplemented in TCM-199 culture medium, and IVF bovine ova were cultured with the media for 6 or 7 days, respectively. The culture media of each group were evaluated for EPF activity by the bovine-rosette inhibition test 48 hr after IVF. The cleavage rate of each group was calculated at 48 hr, and 6 or 7 days after IVF. The culture medium of cumulus cells was also tested for EPF activity.

RESULTS

Only the pregnant bovine sera were EPF positive. All the culture media 48 hr after IVF became EPF positive. Additionally, the culture medium of cumulus cells did not have EPF activity. There was no significant difference in the cleavage rate of the EPF-positive and -negative sera 48 hr after IVF. However, the cleavage rate of EPF-positive sera tended to be higher than the negative sera. In contrast, the blastocyst development rates of EPF-positive sera were significantly higher than those of the negative sera 6 to 7 days after IVF (P < 0.05).

CONCLUSIONS

The data suggest that an EPF-like substance(s) may be secreted from the in vitro fertilized bovine ovum but not from the cumulus cell, and that the EPF in the pregnant serum may accelerate the development of the bovine embryo in IVF.

Embryo associated immunosuppressor factor (EASF) and serum estradiol synergism in pre-embryonic development after in vitro fertilization

The aim of this study was to test whether the level of serum immunosuppressor factor (EASF) and serum estradiol (E2) play a cooperative role in the pre-implantation early embryonic development in IVF-patients. Serum samples were collected from 80 patients undergoing IVF-ET and the level of EASF in patient's sera was assayed using a two-site sandwich enzyme linked immunosorbent assay (ELISA) system. Two-hundred fifty-one IVF-culture media were obtained from these patients and the EASF activity was measured using concanavalin A-induced lymphocyte proliferation assay. EASF activity in embryo growth media, quality of ova, number of cells in each pre-embryo at the time of embryo transfer, cycle day 3 serum E2 and peak E2 levels were correlated with pregnancy outcome. Thirty-three out of 80 patients had detectable levels of serum EASF. The number of pre-embryos with > 4 cell stage at the time of embryo transfer correlated with the total number of ova retrieved in patients positive for serum EASF (P = 0.01) and patients that had an ongoing pregnancy at 7-8 weeks (P < 0.01). Ratio of the number of pre-embryos with > 4 cell stage at the time of embryo transfer and total number of ova retrieved correlated with cycle day 3 serum E2 (P < 0.01) and peak E2 (P = 0.01) levels only in patients positive for EASF. The EASF activity of embryo growth media correlated with cycle day 3 serum E2 (P = 0.0001) and peak E2 (P = 0.007) levels only in patients that were positive for EASF and got pregnant after IVF-ET. This study suggests that the levels of serum EASF and E2 may act synergistically in the development of early embryo.

High levels of spermine in IVF medium as a negative predictor of subsequent success of embryo transfer

PURPOSE

Our purpose was to test the prediction that spermine levels in IVF culture supernatants measure by rapid ELISA assay correlate with subsequent success or failure to establish a pregnancy.

RESULTS

Forty-nine patients undergoing gonadotropin-stimulated ovulation after LHRH analogue treatment in the current study succeeded and 57 failed. With the exception of the first 4 hr of culture, where polyamine levels were slightly (but not significantly) higher in supernatants associated with subsequent success, higher levels of polyamines were predictive of failure.

CONCLUSIONS

The result in this study differs from previous data obtained with women ovulated using clomiphene where low spermine levels (assayed in an immunosuppression assay in vitro) correlated with failure to establish pregnancy, and detectable levels correlated with success. Supplementation of IVF culture medium with spermine and/or spermidine appears unlikely to improve IVF success rates, where the success rate is already very good, and may possibly do harm. The possibility that different methods of ovulation affect subsequent polyamine production in vitro by fertilized oocytes merits further study.

Embryo-associated immunosuppressor factor is produced at the maternal-fetal interface in human pregnancy

PROBLEM

To study whether embryo associated immunosuppressor factor (EASF) is synthesized at the maternal-fetal interface.

METHOD

Anti-EASF monoclonal antibody H5D12 was used to identify EASF. Paraffin-embedded sections were prepared from placental and fetal tissues and immunohistochemistry was done by the avidin-biotin-peroxidase technique. EASF was affinity purified using H5D12-Sepharose 4B from culture media of placental villi and analyzed for immunosuppressive activity (by Concanavalin A-induced lymphocyte proliferation assay) and molecular weight identity (by metabolic labeling studies with 35S-methionine followed by immunoprecipitation and SDS-PAGE).

RESULTS

Immunohistochemical studies demonstrates intense immunostaining of villous syncytiotrophoblast and cytotrophoblast cells of first trimester placental tissues. Hoffbauer cells and decidual cells stained positive. The same cells in second and third trimester placental tissues stained weakly. However, the endothelium and smooth muscle cells of fetal blood vessels, fetal ovarian stroma and primordial follicles, kidney epithelium, cerebral neurons, and glial cells all stained negative. The affinity-purified EASF from the conditioned media of placental villi (less than 12 wk gestational age) was identified as a 37-kDa molecule with immunosuppressive activity. Metabolic labeling studies revealed that placental villi from early gestational age secretes a major factor of 37-kDa and minor factors of 41-kDa and 47-kDa molecular weight.

CONCLUSIONS

Monoclonal antibody H5D12 identifies a factor that is produced by the pre-implantation embryo and also synthesized by decidua and trophoblast cells.

A novel bioassay for detection of preimplantation factor (PIF)

PROBLEM

To identify the presence of vital preimplantation embryos in vivo in humans, a newly observed phenomenon based on autorosette formation between lymphocytes and platelets, when treated with pregnant sera, was used as a marker.

METHOD

Serum samples were obtained from 65 patients on the fourth day after embryo transfer (ET). Sera from 10 healthy males and 47 nonpregnant women were used as controls. The preimplantation factor (PIF) was detected by using blood group O+ donor lymphocytes and platelets incubated with blinded serum in the presence of anti-CD2 antibody and rabbit complement. Human chorion gonadotropin (hCG) concentrations were determined 7 days later and compared with results of the lymphocyte-platelets assay. Implantation was confirmed by ultrasonographic evidence of presence of an intrauterine gestational sac. The role of platelet activating factor (PAF) in the observed phenomena was studied experimentally.

RESULTS

Significantly more lymphocyte-platelet rosette formations were observed when sera from women who successfully implanted were compared to sera from women who failed to implant. This assay yielded a specificity of 95%, sensitivity of 88%, positive predictive value of 94%, and negative predictability of 90%. PAF added directly to the cell suspension and tested sera controls did not influence the percentage of lymphocyte/platelets rosettes.

CONCLUSION

The application of PIF assay will enable the identification and study of early pregnancy events before the implantation occur. PAF by itself is not responsible for the rosette formation.

H5D12 monoclonal antibody identifies a 24-kD immunosuppressor factor produced by human chorio carcinoma cells

PROBLEM

The purpose of this study was to identify and characterize embryo-associated immunosuppressor factor (EASF) secreted by chorio carcinoma cells with the help of EASF-specific monoclonal antibody H5D12 (raised against EASF purified from embryo growth media of in vitro fertilized human ova).

METHOD

Paraffin-embedded slides of human chorio carcinoma as well as control cell lines were prepared, and immunohistochemistry was done by the avidin-biotin-peroxidase technique. EASF was affinity purified using H5D12-Sepharose 4B from culture media of cell lines and analyzed for immunosuppressive activity (by Concanavalin-A-induced lymphocyte proliferation assay) and molecular weight identity (by metabolic-labelling studies with 35S-methionine followed by immunoprecipitation and SDS-PAGE).

RESULTS

H5D12 showed intense immunostaining of BeWo chorio carcinoma cells. Biosynthetic labeling studies identifies this factor as a 24-kD molecule, and EASF bioassay indicates that this factor possesses immunosuppressive activity. No such immunosuppressive activity or similar molecules were identified when control cell lines were analyzed.

CONCLUSIONS

Monoclonal antibody H5D12 recognizes a 24-kD factor with immunosuppressive activity that is secreted by chorio carcinoma cells, which suggests that this is a unique factor and may be one of the key regulators of reproductive functions.

The purification of early-pregnancy factor to homogeneity from human platelets and identification as chaperonin 10

Early-pregnancy factor (EPF), first discovered in the early stages of gestation, is associated with and necessary for cell proliferation in a wide variety of biological situations. Like many other growth factors, EPF is present in platelets, and, by titration studies with a neutralising anti-EPF monoclonal antibody, platelets were identified as an extremely rich source of this growth factor. EPF has been purified from clinically outdated human platelets by heat extraction, ion-exchange and affinity chromatographies on SP-Sephadex and heparin-Sepharose respectively, high-performance hydrophobic interaction chromatography and three reverse-phase HPLC steps, with an average yield of 15 micrograms/100 platelet units (equivalent to approximately 50 1 blood). Using SDS/PAGE, EPF migrated as a single band with approximate M(r) 8500, coincident with biological activity. Mass spectrometry provided an accurate and precise determination of the molecular mass as M(r) 10843.5 +/- 2, along with definitive evidence of the homogeneity of the preparation. Attempts at Edman degradation indicated that the molecule was blocked at the N-terminus and sequencing of proteolytic fragments was undertaken. The amino acid sequence of approximately 70% of the molecule was determined which, with a single exception, is identical with rat chaperonin 10. This structural relationship was shown to extend to functional identity by studies using chaperonin 10 and its functional associate chaperonin 60. Investigations with the latter confirmed that chaperonin 10 is the moiety in pregnancy serum which initiates response in the EPF bioassay. Our studies identify EPF as a member of the highly conserved heat-shock family of molecules and demonstrate a molecular chaperone performing an extracellular role.

Human embryo associated immunosuppressor factor and serum estradiol synergism in ovarian follicle development

PROBLEM

The purpose of this study was to test whether the level of serum immunosuppressor factor (EASF) correlates with ovarian follicle development and with serum hormones during the ovarian cycle.

METHOD

One hundred seventy-three serum samples were collected starting at the time of ovulation and 1 wk after insemination from 29 women attempting pregnancy by ovarian hyperstimulation and intrauterine insemination. After ovarian stimulation, the patients were given human chorionic gonadotropin (hCG) 38 h before insemination. Number and size of follicles were measured by ultrasound. Serum samples were tested for hCG, estradiol (E2), luteinizing hormone, follicle-stimulating hormone (FSH), and progesterone levels. The level of EASF in patients' sera was assayed using a two-site sandwich enzyme-linked immunosorbent assay system. The levels of different hormones and EASF were then correlated among themselves and with the number of ovarian follicles.

RESULTS

Eleven out of 29 patients had detectable levels of serum EASF-Patients positive for EASF had a significantly higher number ovarian follicles > or = 13 mm and E2 levels after hCG treatment as compared to patients with no detectable EASF. The levels of EASF correlated with number of follicles (P = .001), blood E2 (P < .02) and FSH levels (P < .02). Number of follicles > or = 13 mm correlated with E2 (P = .01) and FSH levels (P < .01) only in patients positive for EASF.

CONCLUSIONS

The levels of EASF, E2; and FSH may act synergistically in the development of ovarian follicles.

Production and characterization of monoclonal antibodies to embryo-associated immunosuppressor factor (EASF) produced by human pre-implantation embryo

Balb/c mice were immunized with pre-implantation embryo-associated immunosuppressor factor (EASF) (purified from embryo growth media of in vitro fertilized human ova). Hybridoma clones were produced by fusing their spleen cells with NS1 and P3X653 myeloma cell lines. The presence of specific anti-EASF monoclonal antibodies (mAb) in the hybridoma culture supernatants were tested by enzyme-linked immunosorbent assay. A total of 15 hybridoma clones were selected, and their products were purified and characterized. Each mAb bound specifically to its antigen in a dose-dependent manner. The affinity-purified EASF from embryo growth media demonstrated immunosuppressive activity on Concanavalin A-induced lymphocytes and the presence of 14 kDa, 24 kDa and 37 kDa factors. No such activity or similar molecules were identified when control growth media were analyzed. This clearly demonstrates that these mAb are indeed EASF-specific and are able to recognize biologically active immunosuppressive components in embryo growth media. These mAbs are presently being tested for the development of EASF-specific assay system.

Immunosuppressive 30-kDa protein in urine of pregnant women and patients with trophoblastic diseases

Urine samples obtained from normal pregnant women and patients with trophoblastic diseases contain 30-kDa protein that suppresses phytohemagglutinin-induced T cell proliferation. The immunosuppressive protein was measured by a newly developed radioimmunoassay. The 30-kDa protein was demonstrated in almost all urine samples examined, fluid from hydatid vesicles and chorionic extracts, but not in any serum samples except at low levels in some sera from patients with choriocarcinoma. During pregnancy, the level of urinary 30-kDa protein was higher in the first (1625.5 +/- 1212.0 ng/ml, mean +/- S.D.) and second (1457.4 +/- 1332.4 ng/ml) trimesters than in the third trimester (460.6 +/- 419.0 ng/ml). The urinary 30-kDa protein/hCG ratios in patients with choriocarcinoma (8.3 +/- 10.9) were significantly higher than those in patients with hydatidiform mole (0.67 +/- 1.00, P < 0.01) and in all trimesters than those of normal pregnant women (0.54 +/- 0.44 in first trimester, P < 0.05; 0.63 +/- 0.46 in the second trimester, P < 0.05; 0.24 +/- 0.17 in the third trimester, P < 0.01). There is no significant difference between the ratios in hydatidiform mole and normal pregnancy. These findings and the fast disappearance of the 30-kDa protein from the circulation suggest that the 30-kDa protein plays a part in proliferation of trophoblastic cells in, or their invasion into the host by locally suppressing the immune reaction of the host and that the increase in the urinary 30-kDa protein level, in cases of choriocarcinoma, may be due to the malignant transformation of trophoblastic cells resulting in their rapid invasion.

A study of early pregnancy factor activity in the sera of patients with unexplained spontaneous abortion

PROBLEM

Seventy-seven sera samples obtained from 51 patients (6-20 wk gestation) with unexplained spontaneous abortions including 20 threatened abortions (TA), 13 inevitable abortions (IA), and 18 intrauterine fetal growth retardation (IFGR), as well as 9 sera from 9 patients (6-20 wk gestation) with hydatidiform mole (HM), were detected for early pregnancy factor (EPF) by rosette inhibition assay. Rosette inhibition titer (RIT) was used to express EPF activity.

RESULTS

The RIT value of EPF was 5.95 +/- 0.69 (mean +/- SD) in the TA group; 4.06 +/- 0.93 in the IA group; 3.50 +/- 0.71 in the IFGR group, and 4.00 +/- 0.71 in the HM group. Except for the TA group, in which the mean RIT was in normal pregnancy range, the RIT in the other three groups was significantly lower (P < 0.01) then that of the normal pregnancy group (5.81 +/- 0.68).

CONCLUSIONS

These results suggest that measurement of EPF is a sensitive method for judging survival of the embryo. It may be used to predict the prognosis of the patient with unexplained spontaneous abortion.

Embryo associated immunosuppressor factor(s) secreted by preembryo and serum estradiol levels are predictive of pregnancy outcome: effect of gonadotropin releasing hormone agonist (GnRHa) treatment of patients undergoing in vitro fertilization and embryo transfer (IVF-ET)

The aim of the present study was to determine whether (i) the secretion of embryo associated immunosuppressor factor (EASF) by preimplantation embryo and serum estradiol (E2) play a cooperative role in pregnancy outcome and (ii) whether this association was affected by gonadotropin releasing hormone agonist (GnRHa) pretreatment of IVF-patients for ovarian stimulation. EASF activity was measured using concanavalin A-induced lymphocyte proliferation assay in 251 IVF-culture media obtained from 59 patients undergoing IVF-ET. EASF activity in embryo growth media, cycle day 3 serum E2 level and peak E2 levels were correlated with pregnancy outcome. Results indicate that in GnRHa non-treated patients (i) the immunosuppressive activity of embryo growth media significantly (p less than 0.05) differed between the patients with varying concentration of day 3 serum E2, (ii) the presence of immunosuppressive activity in the embryo growth media was associated with success of pregnancy in patients with day 3 serum E2 level of 21-40 pg/ml (p less than 0.005) and in patients with peak E2 level in serum of less than = 1500 pg/ml (p less than 0.05). No association in immunosuppressive activity, serum E2 level and successful pregnancy was seen in GnRHa treated patients. This preliminary study suggests that the concentration of serum hormones and factors that are altered due to GnRHa pretreatment of IVF-patients may affect the cooperative role played by EASF, E2 and other factors in the success of pregnancy.

Properties of human pre- and post-implantation embryo-associated immunosuppressor factor(s)

Embryo-associated immunosuppressor factor (EASF), a factor detected by its suppressive property on the concanavalin A (ConA) stimulated lymphocyte proliferation assay, was purified from human embryo growth media of in vitro fertilized ova (pre-implantation source) and from pregnancy sera (post-implantation source) as 3 fractions, CM-1, CM-3 and CM-6, the immunosuppressive properties of which were studied. The results show that, (i) the 3 fractions of EASF from both sources suppressed ConA- and pokeweed mitogen (PWM)-induced lymphocyte proliferation, suggesting that they have suppressive effects on both T and B cells; (ii) all 3 EASFs were suppressive when added at the early phase of ConA-supplemented cultures; (iii) CM-1 of both sources were suppressive when added to PWM-supplemented cultures between 24 and 48 h; and (iv) CM-6 of both sources showed an irreversible immunosuppressive effect on PWM-induced lymphocyte proliferation, demonstrating that some similarities exist in the immunosuppressive property of EASF from the 2 sources. On the other hand, (i) CM-6 of pre- and post-implantation EASF were immunosuppressive when added to the PWM-supplemented cultures at 24-48 h and 0-16 h, respectively; and (ii) the CM-6 fraction of pregnancy sera, but not the CM-6 fraction of embryo growth media, possessed an irreversible immunosuppressive effect on ConA-supplemented cultures. This active process by which EASF affects T cell and B cell functions directly may be one of several responses by which the maternal immune response against the fetus is prevented.

Role of embryonic factors in implantation: recent developments

The embryonic factors influencing implantation have been studied extensively in laboratory and domestic animals, but not in primates, including humans. Species differences make extrapolation inadvisable. Embryonic factors affecting implantation include intrinsic features of the embryo, such as its genetic constitution, morphology and hatching. Abnormal genetic constitutions or unsuccessful transitions from maternal to embryonic transcription could account for many failures of early embryonic growth and implantation. Morphology per se does not greatly influence implantation, except when it reflects an abnormal genetic constitution, e.g. in severe fragmentation, although subtle effects may be detected as experimental techniques are refined. The initiation of differentiation and intraembryonic communication between cells and cell types has been studied in animal embryos. Signals must be exchanged between the embryo and the mother to ensure satisfactory implantation. These could include platelet activating factor, prostaglandins, histamine related factors, steroids, proteins, metabolic products and immune-active factors. No one factor seems to be totally responsible for alerting the mother to the presence of an embryo, and a concerted action of these and other agents is probably responsible. The process of implantation itself is poorly understood because of a lack of adequate experimental models. The expression of complementary proteins and the role of specific enzymes and markers of endometrial and embryonic competence are factors well worthy of further study. Knowledge about human implantation is increasing because of recent developments in assisted reproductive technology, and concepts arising from many years of research in animals should find clinical applications in understanding and controlling human reproduction.

The partially purified pre-implantation suppressor factor may be one of several factors to play a role in successful pregnancy

Embryo-associated immunosuppressor factor (EASF) is detected by its suppressive properties in the concanavalin A (ConA)-induced lymphocyte proliferation assay. EASF was partially purified from human embryo growth media of in vitro fertilized ova (pre-implantation EASF) as three fractions. The aim of the present study was to determine whether the EASF isolated from human embryo growth media is similar to the EASF secreted by the pre-embryo, which has been shown to be associated with successful pregnancy. EASF activity was measured in the purified pre-implantation EASF fractions and in a total of 24 individual embryo growth media obtained from 10 patients undergoing in vitro fertilization and embryo transfer, where 6 patients achieved successful pregnancy and 4 did not. The results show that: (i) all three EASF fractions and the individual embryo growth media from patients who became pregnant were suppressive when added to the early phase of ConA-supplemented cultures; this was not seen with the embryo growth media from patients who failed to become pregnant, suggesting that the purified pre-implantation EASF may be one of several factors responsible for successful pregnancy; and (ii) some embryo growth media, irrespective of the pregnancy outcome of the patient, showed an irreversible immunosuppressive effect on ConA-induced lymphocyte proliferation, whereas none of the purified EASF fractions did; this could be due to the loss of activity during purification.

Blood constituents during the estrous cycle and early pregnancy in dairy cows

The objective of this study was to determine if maternal platelet count, white blood cell count or other blood constituents undergo sustained alterations in concentration following fertilization. Blood samples from 17 Holstein females were collected over an 18-d period starting at estrus. Blood was analyzed for levels of platelets, white blood cells, red blood cells, hemoglobin and hematocrit. Results were analyzed for differences between nonpregnant and pregnant groups. Analysis of variance revealed a day-by-group interaction in the platelet count (P<0.01). White blood cell count showed both a day-by-group interaction and a difference between days (P<0.01). Red blood cell count, hematocrit and hemoglobin levels resulted in no significant difference between the two groups (P>0.05). While statistically significant differences were observed in platelet and white blood cell count, neither of these were sustained over a period longer than 2 d.

Immunosuppressive activity in human embryo growth media is associated with successful pregnancy: effect of gonadotropin releasing hormone agonist (GnRHa) treatment of patients undergoing in vitro fertilization and embryo transfer (IVF-ET)

The aim of the present study was to determine whether the secretion of embryo-associated immunosuppressor factor (EASF) by preimplantation embryo correlates with pregnancy outcome and whether this relationship is influenced by pretreatment of gonadotropin releasing hormone agonist (GnRHa) in patients undergoing in vitro fertilization and embryo transfer (IVF-ET). EASF activity was measured using concanavalin A-induced human lymphocyte proliferation assay in 256 embryo growth media obtained from 61 patients undergoing IVF-ET. EASF activity was then correlated with GnRHa treatment and pregnancy outcome in these IVF patients. Results indicate that (i) the presence of immunosuppressive activity in human embryo growth media is associated with success of pregnancy in GnRHa nontreated patients and (ii) serum factors present in GnRHa-treated patients may affect the EASF secretion by preembryos in vitro.