Two fetal antigens (FA-1 and FA-2) and endometrial proteins (PP12 and PP14) isolated from amniotic fluid: localisation in the fetus and adult female genital tract

Glycoprotein and carbohydrate binding protein expression in the placenta in early pregnancy loss

Glycoproteins expressed at the fetal-maternal interface have been shown to exert immunomodulating effects. Glycodelin, hCG and transferrin have been used in in vitro experiments as ligands to block E-selectin-mediated cell adhesion. We found that glycodelin is a strong inhibitor of the E-selectin-mediated cell adhesion with a 10(3)-fold increase in potency compared to the monovalent tetrasaccharide sialyl Lewis X. HCG with distinct carbohydrate expression is also an effective selectin antagonist, whereas the potency of transferrin is low. This could indicate a possible role of glycodelin, hCG and transferrin in preventing leukocyte adhesion to the fetal trophoblast. In decidual tissue of abortion patients, glycodelin expression was significantly reduced compared to normal gestation. These results were confirmed by in situ hybridization. Moreover, glycodelin expression in endometrial cells in vitro could be stimulated by addition of hCG. Because hCG is down-regulated in women with abortion, we speculate that hCG could be one of the factors regulating glycodelin expression. Galectins are structurally related proteins with the ability to bind beta-galactosides through a conserved carbohydrate recognition domain. Galectin-1 (gal-1) expression in the syncytiotrophoblast is down-regulated in early pregnancy loss. Gal-1 recognizes the Thomsen-Friedenreich disaccharide (Galbeta1-3GalNAc-) on the syncytiotrophoblast and extravillous trophoblast. Gal-1 also inhibited trophoblast cell proliferation but did not induce apoptosis in BeWo cells. Ligation of Gal-1 on trophoblast cells may have regulatory effects on trophoblast cell differentiation. Decreased expression of Gal-1 may partly explain disturbed trophoblast differentiation during early placentation leading to early pregnancy loss.

Endometrial protein PP14: a new test of endometrial function?

The human endometrium produces a number of proteins which are at least partly specific to that tissue. Two of these proteins have been the subject of much recent work. They were originally called ‘placental protein 12’ and ‘placental protein 14’ (PP12 and PP14) because they were isolated by Hans Bohn from extracts of whole placentae. However, it is now clear that they arise from the maternal endometrium (decidua) rather than the fetal trophoblast. Placental protein 12 has been shown to be identical to the insulin-like growth factor binding protein-1 (IGFBP-1). It is produced in many normal tissues and its measurement probably does not provide a specific index of endometrial function. By contrast, PP14 is detectable only in ‘reproductive’ tissues and, in theory, might be an excellent clinical test of endometrial function.

Changes in T-plastin expression with human trophoblast differentiation

During the first trimester of pregnancy, the human placenta is an actively dividing and highly invasive tumour-like tissue, while near term, it represents a fully developed, non-invasive unit. In order to understand the molecular basis of this marked difference in the placental phenotypes, an approach based on a differential display-reverse transcription-polymerase chain reaction (DD-RT-PCR) was adopted to analyse changes in gene expression, using total RNA isolated from first-trimester and term placental villi. Using this approach, T-plastin was initially identified as being differentially expressed in the human first-trimester placenta. T-plastin is an actin-bundling protein and is known to be highly expressed in actively dividing cells and up-regulated in several carcinomas. Using a homogenous population of cytotrophoblasts and syncytiotrophoblasts isolated from human placentae, the present authors demonstrate the differential expression of T-plastin in cytotrophoblasts compared with the terminally differentiated syncytiotrophoblasts. The down-regulation of T-plastin expression is further demonstrated in human trophoblastic BeWo cells induced to differentiate using transforming growth factor (TGF)beta1, a growth factor known for its anti-proliferative and anti-invasive response in placental cells. These studies suggest that expression of T-plastin in the placental context may indeed be associated with the enhanced replicative potential of placental trophoblasts.

High Prevalence of Human Anti‐bovine IgG Antibodies as the Major Cause of False Positive Reactions in Two‐Site Immunoassays Based on Monoclonal Antibodies

A sandwich ELISA for quantification of the endometrial protein PP14 revealed false positive reactions in 81% of male sera (n = 54). The PP14 ELISA was based on two monoclonal antibodies (Mabs) with different epitope specificities--a catcher and a biotinylated indicator. The monoclonal antibodies were purified by protein G affinity chromatography from culture supernatant containing 10% (v/v) fetal calf serum (FCS). Human anti-animal IgG (bovine, mouse, horse, and swine) antibodies and human anti-bovine serum albumin antibodies were measured using an ELISA design, with direct bridging of the solid phase and biotinylated antigens. The false positive reactions were abolished by addition of 1% (v/v) bovine serum to the dilution buffer (DB). Human anti-bovine IgG antibodies (HABIA) were detected in 99 out of 104 sera from blood donors (50 females; 54 males). HABIA levels in male sera (n = 54) were positively correlated to the false positive signals in the PP14 ELISA (r = 0.923; p < 0.0001). Antibodies to IgG from other mammalian species (mouse, horse, and swine) were also detected in the donor sera, but levels and frequencies were lower compared to that of HABIA. Furthermore, HABIA were positively correlated to human anti-bovine serum albumin antibodies in the donor sera (r = 0.639; p < 0.0001; n = 103). HABIA (prevalence 95%) cause false positive reactions due to crossbinding of contaminating bovine IgG and/or crossreaction with mouse IgG in two-site immunoassays. The apparent presence of human anti-mouse IgG antibodies (HAMA), described to create false positive results, may be due to a crossreacting fraction of the polyclonal circulating antibodies against bovine IgG.

Extracellular matrix building marked by the N-terminal propeptide of procollagen type I reflect aggressiveness of recurrent breast cancer

The purpose of our study was to examine the association between extracellular matrix homeostasis and aggressive breast cancer as reflected by the synthesis of type I collagen marked by circulating concentration of the aminoterminal propeptide of type I procollagen (PINP). Pre-therapeutic serum PINP concentrations were measured in 154 healthy women and 100 patients referred with their first metastatic manifestation of breast cancer and correlated to the metastatic pattern, response to therapy, time to progression and survival with a minimal follow-up of 5 years. Fifty-four percent of the patients had serum PINP concentrations greater than the 95th percentile of the healthy controls and 38% were high PINP level patients with values clearly outside normal range (>125 ng/ml). Patients with high PINP levels were more sick (p = 0.002), had a higher tumor burden (p = 0.013) and revealed a lower responsiveness to anthracycline-based therapy (p = 0.0002) as well as an accelerated time to disease progression (p = 0.00001) and death (p = 0.0006). Median survival in the high serum PINP level group was less than half of that in the group with low PINP level (14.5 vs. 32 months). The lowest PINP levels were seen when the cancer was restricted to the lymph node and skin and increasing PINP levels were found if the cancer had spread to the lungs, the bones, the bone marrow and the liver. High PINP level at recurrence and lack of estrogen receptors (ER) independently reflected aggressive tumor behavior after recurrence with an equal great impact on time to progression and survival. Patients with a high PINP level and primarily ER-negative tumors survived a median of only 6 months with no one alive after 22 months. By contrast patients with a low PINP level and ER-positive tumors had a median survival of 37 months and 23% were still alive after 5 years. Aggressive breast cancer induces a strong fibroproliferative response with synthesis of type I collagen. Serum PINP levels may be a diagnostic and prognostic tool that indicate breast cancer activity, aggressiveness, expansion and metastasis and a predictor of outcome after anthracycline-based chemotherapy.

IGFBP-1 and glycodelin serum levels before and after hysterectomy with and without bilateral oophorectomy in premenopausal women

OBJECTIVES

The aim of our study was to investigate the role of the intact endometrium and ovaries for serum levels of insulin-like growth factor binding protein-1 (IGFBP-1) and glycodelin.

STUDY DESIGN

In 35 premenopausal patients with a planned hysterectomy, serum measurements of IGFBP-1 and glycodelin were done before surgery and 1, 3, 5, and 10 days after surgery. Patients were divided into three groups according to the kind and time of operation: (1) hysterectomy with bilateral adnexectomy in the luteal phase and (2) hysterectomy without adnexectomy in the follicular phase or (3) the luteal phase.

RESULTS

IGFBP-1-we could not show any differences in IGFBP-1 serum levels before and after hysterectomy with or without bilateral oophorectomy. Glycodelin-hysterectomized and oophorectomized patients showed decreasing serum levels up to day 3. After day 5, circulating concentrations of glycodelin increased continuously but remained below pre-operative levels. In both non-adnexectomized groups we saw a reduction up to day 5 but a rise at day 10. None of the results reached statistical significance.

CONCLUSION

The results indicate that endometrium and ovary are not the only sources of IGFBP-1 and glycodelin.

Fetal antigen 1 in healthy adults and patients with pituitary disease: relation to physiological, pathological, and pharmacological GH levels

Immunohistochemical analysis of the distribution of human fetal antigen 1 (FA1) in adult human tissues has demonstrated a strong association between FA1 and (neuro)endocrine structures. In the anterior pituitary gland FA1 was colocalized with GH, and the present study was performed to evaluate a possible relationship between GH and FA1. FA1 and GH levels were measured during a 24-h period at 20-min intervals. In contrast to the known GH peaks during 24-h sampling, there was no detectable FA1 peak. The FA1 responses to placebo were not significantly different from the responses to the combination of pyridostigmine and GHRH. No significant difference was found between basal FA1 (nanograms per ml) levels [median (minimum-maximum)] in healthy adults [n = 40; 28.6 ng/ml (12.5-72.0)], acromegalic patients [n = 11; 31.0 ng/ml (21.6-56.3)], and patients with GH deficiency [n = 22; 32.1 ng/ml (13.4-108.7)]. FA1 levels were significantly reduced, in the six of seven acromegalic GH responders to octreotide, from [median (minimum-maximum)] 30.6 ng/ml (20.0-43.1) to 20.3 (13.9-30.2; P < 0.02). There was no significant change during placebo. FA1 levels were significantly increased compared with placebo values during 3 months of GH therapy. The increase in FA1 levels was significantly higher than the change during placebo (P < 0.003). In conclusion, a common secretory and stimulatory pathway for FA1 and GH in healthy adults has been ruled out. However, we found that pharmacologically induced changes in GH levels during weeks to months had a corresponding direct or indirect effect on FA1 levels in patients with GH deficiency or acromegaly. However, a direct effect of octreotide on FA1 levels, independent of GH levels, has not been ruled out.

Does fetal antigen 1 (FA1) identify cells with regenerative, endocrine and neuroendocrine potentials? A study of FA1 in embryonic, fetal, and placental tissue and in maternal circulation

Fetal antigen 1 (FA1) is a circulating EGF multidomain glycoprotein. FA1 and its membrane-associated precursor is defined by the mRNAs referred to as delta-like (dlk), preadipocyte factor 1 (pref-1) or zona glomerulosa-specific factor (ZOG). Using a polyclonal antibody recognising both forms, the localisation of FA1/dlk was analysed in embryonic and fetal tissues between week 5 to 25 of gestation and related to germinal origin and development. FA1 was observed in endodermally derived hepatocytes, glandular cells of the pancreas anlage, and in respiratory epithelial cells. FA1 was also present in mesodermally derived cells of the renal proximal tubules, adrenal cortex, Leydig and Hilus cells of the testes and ovaries, fetal chondroblasts, and skeletal myotubes. Ectodermally derived neuro- and adenohypophysial cells, cells in the floor of the 3rd ventricle and plexus choroideus were also FA1 positive. The number of cells expressing FA1 decreased during fetal development where the expression became restricted to specific functional cells. Epidermis, gut epithelium, gall bladder, blood cells, spleen, thyroid gland, salivary glands, and smooth muscle cells were FA1 negative. Analysis of extra-embryonic tissues from normal and pathological pregnancies revealed FA1 in stromal cells surrounding the blood islands of the yolk sac as well as in placental fibroblasts where the expression was most pronounced in diploid, androgenic complete hydatidiform moles. However, as measured by ELISA, the circulating maternal FA1 levels in complete moles were not different from normal pregnancies. The results presented suggest that FA1 is a growth and/or differentiation factor extensively expressed in immature cells and down-regulated during fetal development. FA1 down-regulation was associated with a shift in the subcellular localisation indicating differential post-translational/post-transcriptional modifications during fetal development. FA1 may be a new marker of cellular subtypes with a regenerative potential and of specific cells with endocrine or neuroendocrine functions.

Purification, characterization, and biological compartmentalization of rat fetal antigen 1

This study has established the rat as an animal model for the analysis of the biological role of fetal antigen 1 (FA1), a protein previously described in humans and mice. FA1 was purified from rat amniotic fluid by immunospecific affinity chromatography. Immunochemical identity between mouse and rat FA1 was established by crossed tandem immunoelectrophoresis. Molecular size was analyzed by mass spectrometry (33 kDa). The amino acid composition was determined, and the amino acid sequence was analyzed. The overall amino acid composition and sequence of the 28 first N-terminal amino acids were identical to the corresponding parts of rat preadipocyte factor 1 and rat adrenal zona glomerulosa protein. Extensive sequence similarity was found between rat and mouse FA1 (86%) and between rat and human FA1 (82%). The concentration of FA1 in fetal serum, maternal serum, urine, and amniotic fluid in rats was determined using an ELISA. The highest concentrations were found in fetal serum and amniotic fluid around Day 18 of pregnancy. This is the first report on the physicochemical characteristics and compartmentalization of rat FA1.

Fetal antigen 1 (FA1), a circulating member of the epidermal growth factor (EGF) superfamily: ELISA development, physiology and metabolism in relation to renal function

We describe an ELISA technique for quantification of fetal antigen 1 (FA1), a glycoprotein belonging to the EGF-superfamily. The ELISA is based on immunospecifically purified polyclonal antibodies and has a dynamic range of 0.7-5.3 ng/ml, intra- and inter-assay C.V.s of less than 3.2% and an average recovery of 105% in serum and 98% in urine. Comparison of FA1 in amniotic fluid, serum and urine revealed parallel titration curves, identical elution volumes following size chromatography, immunological identity and similar profiles when analysed by MALDI-MS. The reference interval for serum FA1 was 12.3-46.6 ng/ml and the levels were 10 times higher in patients with renal failure. FA1 showed no diurnal variation, no variation during the menstrual cycle and was not influenced by the acute phase reaction. In humans (n = 10) the renal clearance of FA1 was 11 ml/min and an identical high renal clearance was found in rats when expressed per 100 g body weight. In rats the initial increase in serum FA1 was 10 ng/ml/h following bilateral nephrectomy, explaining the increased serum concentrations of FA1 observed in patients with renal failure.

Growth hormone and prolactin stimulate the expression of rat preadipocyte factor-1/delta-like protein in pancreatic islets: molecular cloning and expression pattern during development and growth of the endocrine pancreas

GH and PRL have been shown to stimulate proliferation and insulin production in islets of Langerhans. To identify genes regulated by GH/PRL in islets, we performed differential screening of a complementary DNA library from neonatal rat islets cultured for 24 h with human GH (hGH). One hGH-induced clone had 96% identity with mouse preadipocyte factor-1 (Pref-1, or delta-like protein (Dlk)]. The size of Pref-1 messenger RNA (mRNA) in islets was 1.6 kilobases, with two less abundant mRNAs of 3.7 and 6.2 kilobases. The Pref-1 mRNA content of islets from adult rats was only 1% of that in neonatal islets. Pref-1 mRNA was markedly up-regulated in islets from pregnant rats from day 12 to term compared with those from age-matched female rats. Two peaks in mRNA expression were observed during gestation, one on day 14 and the other at term, whereafter it decreased to nonpregnant levels. Pref-1 mRNA was up-regulated 3- to 4-fold in neonatal rat islets of Langerhans after 48-h culture with hGH, as found also with bovine GH or ovine PRL. During the development of pancreas from embryonic day 12 (E12) to postnatal day 4, we observed a 2-fold increase in Pref-1 mRNA on E17 and a 5-fold increase at birth, followed by a rapid decline on postnatal day 4. Pref-1 immunoreactivity was found in a subpopulation of insulin cells of neonatal islets of Langerhans. At an early embryonal stage (E13), most cells of the pancreatic anlage were Pref-1 positive, becoming predominantly restricted to the insulin-producing cells during development. In conclusion, these findings suggest that Pref-1 is involved in both differentiation and growth of beta-cells.

Zona glomerulosa-specific factor: cloning and function

The rat adrenal cortex is composed of three zones: the zona glomerulosa, the zona fasciculata, and the zona reticularis. Several investigators have claimed the presence of a zona intermedia between the zonae glomerulosa and fasciculata. The cells of zona glomerulosa, a few layers of cells just beneath the adrenal capsule, synthesize and secrete aldosterone, whereas those of zonae fasciculata and reticularis secrete glucocorticoids and androgens, respectively. The function of the cells in zona intermedia is unclear, because they express neither aldosterone synthase nor 11 beta-hydroxylase. To investigate the mechanism underlying the zonal differentiation of adrenocortical steroidogenesis, attempts have been made to isolate and characterize zone-specifically expressed proteins such as steroidogenic enzymes and putative regulatory factors. Having subtracted the mRNAs present in the decapsulated adrenal gland from those in the adrenal capsule, we successfully isolated three distinct clones, each specifically expressed in the zona glomerulosa. One clone encoded a protein named zona glomerulosa-specific factor (ZOG), which had a putative signal peptide at the N-terminus, six tandem epidermal growth factor (EGF)-like repeats, and a transmembrane domain in the central portion and a short cytosolic stretch at the C-terminus. Immunohistochemical studies using the antibody raised against ZOG confirmed the presence of the protein in all layers of cells in the zona glomerulosa. In contrast, cells possessing aldosterone synthase were present only in the periphery of zona glomerulosa, just beneath the capsule. These findings suggest that there are at least two kinds of zona glomerulosa cells in the rat adrenal cortex, one expressing aldosterone synthase as well as ZOG, and another expressing only ZOG. The cells in the zona intermedia did not express ZOG, aldosterone synthase, or 11 beta-hydroxylase, but did express Ad4BP. ZOG was not detected in zonae fasciculata and reticularis where 11 beta-hydroxylase was present.

FA1 immunoreactivity in endocrine tumours and during development of the human fetal pancreas; negative correlation with glucagon expression

Fetal antigen 1 (FA1) is a glycoprotein containing six epidermal growth factor (EGF)-like repeats. It is closely similar to the protein translated from the human delta-like (dlk) cDNA and probably constitutes a proteolytically processed form of dlk. dlk is homologous to the Drosophila homeotic proteins delta and notch and to the murine preadipocyte differentiation factor Pref-1. These proteins participate in determining cell fate choices during differentiation. We now report that FA1 immunoreactivity is present in a number of neuroectodermally derived tumours as well as in pancreatic endocrine tumours. A negative correlation between FA1 and glucagon immunoreactants in these tumours prompted a reexamination of FA1 immunoreactants during fetal pancreatic development. At the earliest stages of development, FA1 was expressed by most of the non-endocrine parenchymal cells and, with ensuing development, gradually disappeared from these cells and became restricted to insulin-producing beta cells. Throughout development FA1 was not detected in endocrine glucagon, somatostatin or pancreatic polypeptide cells. Moreover, developing insulin cells that coexpressed glucagon were negative for FA1. Thus, there was a negative correlation between FA1 and glucagon both in tumours and during development. These results, together with FA1/dlk's similarity with homeotic proteins, point to a role of FA1 in islet cell differentiation.

Procollagen type I N-terminal propeptide (PINP) as an indicator of type I collagen metabolism: ELISA development, reference interval, and hypovitaminosis D induced hyperparathyroidism

A sandwich enzyme-linked immunosorbent assay (ELISA) for quantification of the N-terminal propeptide of human procollagen type I (PINP) utilizing purified alpha 1-chain specific rabbit antibodies is described. The ELISA measured the content of the alpha 1-chain of PINP independent of the molecular form of the molecule. A parallelism was found between amniotic fluid (calibrator), normal and patient serum, and purified PINP (alpha 1), as well as the high and low molecular weight forms of PINP (alpha 1). The concentration of PINP in the calibrator (second trimester amniotic fluid) was determined to 25 micrograms/mL and the detection limit was 62 pg/mL measured in amniotic fluid, and 41 pg/mL measured in serum. The interassay coefficients of variation were 4.6% (low control) and 5.3% (high control), and the corresponding intraassay parameters were 2.9% and 4.9%. Recovery studies revealed an accuracy between 93% and 105%. The normal range (n = 57) for PINP was 56 ng/mL (median) the 10th and 90th centiles being 30 and 82 ng/mL, respectively. Patients with hyperparathyroidism due to hypovitaminosis D had median serum level of 168 ng/mL with a 10th centile of 44 ng/mL and a 90th centile of 450 ng/mL, these values being significantly different from the normal range (p < 0.001). The PINP-ELISA was superior to commercially available assays for PICP and osteocalcin in separation between healthy controls and patients with osteomalaci.

The typing of fetal antigen 2 in human amniotic fluid

Fetal antigen 2 (FA-2) has been identified in amniotic fluid and shown to be of fetal origin. In this study we have extended previous observations on FA-2 heterogeneity with respect to both size and charge using gel filtration, ion-exchange chromatography, non-dissociating polyacrylamide gel electrophoresis and sodium dodecyl sulphate polyacrylamide gel electrophoresis. From the diversity of forms we have been able to define two principal FA-2 types, type A and type B. Type A has a high molecular mass (140 kDa), has subunits of 33 kDa and 29 kDa, and elutes at approximately 0.27 mol/l sodium chloride from diethylaminoethyl (DEAE)-Sephacel. Type B has the same mass and subunits as type A, but elutes at approximately 0.24 mol/l sodium chloride from DEAE-Sephacel. Other low molecular mass forms of FA-2 have also been identified. All FA-2 forms described were shown to be common to all amniotic fluid samples studied and were not attributable to artefacts of collection or storage. It was also demonstrated that the recently described FA-2 RIA is specific for FA-2 types A and B and the conversion of arbitrary units FA-2 into micrograms applies to type A. The typing is discussed with respect to (i) the aminopropeptide of the alpha 1 chain of human procollagen type I, (ii) the 24 kDa phosphoprotein in developing bone and (iii) fetal calf ligament protein 1 (FCL-1), suggesting that they are the same protein.

Protein structure of fetal antigen 1 (FA1). A novel circulating human epidermal-growth-factor-like protein expressed in neuroendocrine tumors and its relation to the gene products of dlk and pG2

The present paper describes the primary structure, glycosylation and tissue localization of fetal antigen 1 (FA1) isolated from second-trimester human amniotic fluid. FA1 is a single-chained, heterogeneous glycoprotein of 225-262 amino acid residues. FA1 has six well conserved epidermal-growth-factor motifs and contains up to ten O-glycosylation and N-glycosylation sites, six of which are differentially glycosylated. Alignment to the translated sequences of Mus. musculus dlk and human dlk revealed 86% and 99% identity, respectively, to a 259-amino-acid residue overlap, and this high similarity extends with minor corrections to the human adrenal-specific mRNA, pG2 as well. Immunohistochemical analysis demonstrated the presence of FA1 in 10 out of 14 lung tumors containing neuroendocrine elements, and in the placental villi where FA1 was exclusively seen in stromal cells in close contact to the vascular structure. In the pancreas, FA1 co-localized with insulin in the insulin secretory granules of the beta cells within the islets of Langerhans. Our findings suggest that FA1 is synthesized as a membrane anchored protein and released into the circulation after enzymic cleavage, and that circulating FA1 represents the post-translationally modified gene product of human dlk which, in turn, is identical to human adrenal-specific mRNA pG2.

Immunohistochemical localization of two endometrial proteins in the early days of human pregnancy

Insulin-like growth factor binding protein-1 (IGFBP-1) [also known as placental protein 12(PP12)] and placental protein 14 (PP14) have been identified by specific immunostaining in early pregnancy specimens obtained 13-35 days of gestation. PP12 was evident in a discrete number of stromal decidual cells at the deciduotrophoblastic interface and under the endometrial surface epithelium. These cells did not have the rounded appearance of classic decidual cells but most often displayed cytoplasmic expansions. Staining for PP14 was strictly localized to the glandular epithelium of the endometrium. Implantation of the conceptus may be an important mechanism in the early expression of PP12 but not PP14.

Immunohistochemical markers of uterine receptivity in the human endometrium

The factors responsible for the initial interaction between maternal and fetal epithelium leading to the establishment of pregnancy remain poorly understood. Temporal and spatial expression of specific endometrial peptides in response to ovarian steroids is thought to contribute to the development of a period of uterine receptivity, whereby the endometrium becomes hospitable to the implanting blastocyst. The failure to establish receptivity may account for a significant percentage of the cases of infertility in the female, especially affecting women with luteal phase deficiency, leiomyomata uteri, endometriosis, habitual abortion, and unexplained infertility. In addition, despite increasing global experience with advanced reproductive technologies, the majority of In Vitro Fertilization (IVF) attempts remain unsuccessful, most likely on the basis of implantation failure. In this article, we review the concepts involved in the study of uterine receptivity in the human, highlight potential immunohistochemical (IHC) markers that have recently been discovered, and discuss how IHC assessment of the endometrium is a potentially valuable method for the evaluation of the receptive endometrial state. Using this approach we have examined several new potential markers of uterine receptivity. Endometrial progesterone receptors and one of the integrin cell adhesion molecules appear to undergo changes in expression around the time of implantation, and may be sensitive indicators of the receptive state. Further, these markers are delayed in women with infertility and luteal phase deficiency. These studies illustrate the utility of IHC diagnosis for the evaluation of endometrial function.

Fetal antigen 2: an amniotic protein identified as the aminopropeptide of the alpha 1 chain of human procollagen type I

Fetal antigen (FA2) was purified from second trimester human amniotic fluid by immunospecific chromatography, gel filtration and reversed-phase chromatography. Gel filtration revealed two molecular forms of FA2 eluting at volumes corresponding to an M(r) of approximately 100 kDa and 30 kDa. SDS-PAGE analysis gave an M(r) = 27 kDa under reducing and non-reducing conditions for both forms, whereas the exact M(r) determined by mass spectrometry was 14,343 +/- 3 Da. FA2 was N-terminally blocked and after tryptic digestion the amino acid composition and sequences of the peptides showed identity with the aminopropeptide of the alpha 1 chain of human procollagen type I as determined by nucleotide sequences. After oxidative procedures normally employed for radio-iodination (iodogen and chloramine-T), FA2 lost its immunoreactivity. An antigen which cross-reacted with polyclonal rabbit anti-human FA2 was demonstrated in fetal calf serum. Gel filtration with analysis of fractions by inhibition ELISA showed that the bovine homologue was present in the same molecular forms as those in human amniotic fluid, and immunohistochemical analysis with anti-human FA2 showed that its distribution in bovine skin was identical to that of FA2 in human skin. FA2 is a circulating form of the aminopropeptide of the alpha 1 chain of procollagen type I, and this is the first description of its isolation and structural characterization in humans.

Serum levels of fetal antigen 2 in hyperthyroidism and primary hyperparathyroidism

Serum concentration of fetal antigen 2 (FA2) in patients with hyperthyroidism (n = 18) (median: 12.9 mAU/l; range: 3.2-22.4 mAU/l) was significantly (p < 0.002) higher than in age- and sex-matched healthy controls (median: 4.1 mAU FA2/l; range: 2.4-10.0 mAU FA2/l). Serum FA2 was positively correlated with thyroxine (T4) (Rs = 0.51; p < 0.05), triiodothyronine (T3) (Rs = 0.64; p < 0.01), bone-Gla protein (BGP) (Rs = 0.70; p < 0.01), total alkaline phosphatase (total-AP) (Rs = 0.62; p < 0.01), bone isoenzyme alkaline phosphatase (bone-AP) (Rs = 0.63; p < 0.01), N-terminal procollagen type III (PIIINP) (Rs = 0.65; p < 0.01) and urine OH-proline (OHP) (Rs = 0.79; p < 0.01). In patients with hyperparathyroidism the pretreatment levels of FA2 (n = 8) (median: 17.6 mAU/l; range: 5.2-35.0 mAU/l) were significantly (p < 0.001) higher than those of age- and sex-matched controls (median: 3.7 mAU FA2/l; range: 3.4-9.0 mAU/l). The pretreatment level of FA2 was positively correlated with the parathyroid hormone (PTH) (Rs = 0.80; p < 0.05). Following surgical treatment the serum concentrations of FA2, PTH, and BGP decreased compared to pretreatment levels and the fall in these three parameters revealed parallelism. These data indicate that serum FA2 can be used as a marker in the evaluation of metabolic bone diseases.

Foetal antigen 2 (FA2) in the stromal reaction induced by breast carcinoma

An indirect immunoperoxidase technique was used to examine the distribution of foetal antigen 2 (FA2), a recently described basement membrane (BM)-associated antigen, in invasive breast carcinoma (n = 34), fibroadenoma (n = 5) and normal breast tissue (n = 5), and to compare its distribution with that of laminin and collagen type IV. In normal breast tissue, FA2 was detected in the intralobular stroma as a broad band around acini and ducts, but was not present in the interlobular stroma. In areas of carcinoma in situ, FA2 was present diffusely around and in close contact with the glandular elements, the staining being more intense than that found around normal glandular structures. Two distinct patterns of FA2 distribution were found in adenocarcinomas of the breast. In the fibroblast reaction type, fibroblast staining dominated, whilst in the stromal reaction type, intense and extensive staining of the surrounding stroma dominated. Significant correlation was found between the degree of fibroblast activity and the degree of anaplasia (p = 0.005). FA2 extracted from breast carcinoma tissue was shown to be immunologically identical to FA2 fractions extracted from second trimester amniotic fluid (AF). The Mr of FA2 isolated from AF was estimated to be 26 kD, whereas the Mr of FA2 extracted from breast carcinoma tissue was slightly higher. The apparent Mr under reducing conditions were higher and three bands ranging from 26 to 29 kD were seen. FA2 was found to be immunologically distinct from collagen types I, III and IV, laminin, fibronectin and fibrinogen. The increased production and widespread distribution of FA2 in breast carcinomas suggest that FA2 is involved in the stromal changes which occur in response to tumour growth and/or invasion.

Immunohistochemical studies on the localization of fetal antigen 2 (FA2), laminin, and collagen type 4 in basal cell carcinoma

The localization of fetal antigen 2 (FA2), a recently described basement membrane (BM) associated antigen, was studied by immunohistochemical techniques in 21 basal cell carcinomas (BCC). In both superficial and infiltrating BCC, FA2 was located in a broad diffuse band around the tumor elements and in close contact with the BM. Compared to normal skin, a more extensive distribution of FA2 was seen in BCC. In the infiltrating BCC, FA2 staining was also present in the interstitial stroma between the tumor islands. FA2 was absent in areas with inflammatory cell infiltrates and elastoid degeneration. Epithelial and tumor cells were FA2 negative. The distribution of FA2 was clearly different from that of laminin and collagen type 4. Collagen type 4 and laminin were present as a continuous linear band corresponding to the BM surrounding the tumors. The close contact to the BM and the increased content of FA2 in the reactive stroma around BCC suggest that FA2 is involved in the matrix and/or BM changes taking place during tumor growth and invasion.

Epithelial glycoprotein is a member of a family of epithelial cell surface antigens homologous to nidogen, a matrix adhesion protein

The cell surface antigen, epithelial glycoprotein, defined by the monoclonal antibody HEA 125, is expressed on virtually all epithelial cell membranes but not on mesodermal or neural cell membranes. The cDNA encoding epithelial glycoprotein was isolated by HEA 125 antibody enrichment of colon tumor cDNA expressed transiently in COS cells. The sequence of the epithelial glycoprotein antigen is identical to the cell membrane protein recognized by the monoclonal antibody KS 1/4 and is homologous to the tumor-associated antigen GA733. These proteins share sequence homology to nidogen, an extracellular matrix component that appears to participate in cell-matrix adhesion. These proteins also share a homologous domain found in the B1 chain of laminin, a matrix adhesion protein, and placental protein 12, an insulin-like growth factor I binding protein secreted during pregnancy that has been implicated in regulation of fetal growth. This common domain is also repeated multiple times within the thyroglobulin precursor. These findings suggest epithelial glycoprotein is a cell surface molecule involved in cell-cell or cell-matrix interaction.

Simultaneous autoradiography and line immunoelectrophoresis (ARLIE): a novel combination to identify de novo protein synthesis by pregnancy tissues

A novel combination of two conventional techniques (autoradiography, AR and line immunoelectrophoresis, LIE; ARLIE) for identification of specific proteins synthesized de novo by explants is described. The incorporation rate of [35S]-methionine was linear in proteins derived from cytosol fractions and supernatants of first trimester human trophoblast and gestational endometrium for up to 18 h. SDS-PAGE analysis of these fractions provided further evidence of the protein synthesis and secretion by the tissue explants. The ARLIE system was evaluated by investigating the synthesis and secretion of five test proteins (PP12, PP14, hPL, FA-1 and FA-2) by trophoblast and gestational endometrium. The synthesis P12 and PP14 could be demonstrated by gestational endometrium only. Similarly the synthesis of hPL could be demonstrated by the trophoblast alone. The synthesis of the fetal proteins (FA-1 and FA-2) could not be demonstrated by either tissue. The control procedure, Protein A assisted immunoprecipitation, yielded similar results for PP14 but not hPL. This novel combination (ARLIE) provides a simple technique with which to study the de novo synthesis of several proteins simultaneously which is independent of the subclass and species of origin of antibodies.

Localization of foetal antigen 2 (FA-2) in foetal and adult human skin

Foetal antigen 2 (FA-2) is a connective-tissue-associated antigen isolated from second trimester human amniotic fluid. FA-2 has an alpha-electrophoretic mobility and is a single-chain molecule with a molecular weight of 26 kDa as determined by polyacrylamide gel electrophoresis (PAGE). Using indirect immunofluorescence and the immunoperoxidase technique, FA-2 was found to be in the lamina densa/sublamina densa region of the basement membrane zone (BMZ) in adult as well as in foetal skin. FA-2 was found throughout the dermis in foetal skin, whereas in adult skin it was found to be associated with the BMZ and around the blood vessels, hair follicles and eccrine glands. Intracellular FA-2 antigen was demonstrated in proliferating fibroblasts by the indirect immunoperoxidase technique and immunoelectron microscopy of the fibroblasts revealed staining of the antigen in the cisternae of the rough endoplasmatic reticulum at the trans-side of the Golgi complex as well as in vesicles close to the plasma membranes. FA-2, a hitherto undescribed antigen associated with human BMZ, is probably being synthesized by proliferating fibroblasts.