Radioimmunoassay of maternal serum alpha fetoprotein during pregnancy and delivery

The postresection alpha-fetoprotein in cirrhotic patients with hepatocellular carcinoma. An independent predictor of outcome

BACKGROUND

The postresection alpha-fetoprotein (AFP) in cirrhotic patients with hepatocellular carcinoma (HCC) may predict overall survival (OS) and recurrence beyond Milan criteria (MC) among the subgroup of initially transplantable patients.

METHODS

All patients with cirrhosis resected for HCC between January 1990 and December 2010 in a single institution and presenting a serum AFP value > 15 ng/ml at diagnosis were included. The postresection AFP was analyzed as a dichotomized variable: normalization (norm + group) or not (norm - group) within the 90-day postresection period.

RESULTS

Among 271 resected patients, 141 patients (52%) had a level of serum AFP ≥ 15 ng/ml at diagnosis. Five-year OS and median survival were 42% and 52 months in group norm + versus 20% and 23 months in the group norm - (P = 0.009). On multivariate analysis, the absence of AFP normalization was an independent factor of poor OS as well as microvascular invasion, and satellites nodules. Among theoretically transplantable patients, independent predictors of recurrence beyond MC were the absence of AFP normalization (risk ratio (RR) 5.02 [1.53-16.34]) and microvascular invasion (RR 4.76 [1.42-15.34]).

CONCLUSION

The postresection AFP has an independent prognostic value. Transplantable patients resected for HCC without 90-day AFP normalization should be discussed for early liver transplantation.

A study of oligosaccharide variants of alpha-fetoproteins produced by normal fetuses and fetuses with trisomy 21

BACKGROUND

The mechanisms of the increase in the percentage of alpha-fetoproteins (AFPs) that strongly binds to Lens culinaris agglutinin (AFP-L3) in pregnancies with a trisomy 21 fetus have not been analyzed. To investigate the oligosaccharide variants of AFP produced by normal fetuses and fetuses with trisomy 21, the lectin reactivity of AFP was analyzed.

METHODS

Fetal liver tissue, amniotic fluid, and maternal serum were obtained from five normal pregnancies and five pregnancies with a trisomy 21 fetus. The percentages of AFP reactive to lectins were determined by lectin-affinity electrophoresis coupled with antibody-affinity blotting.

RESULTS

The percentages of AFP-L3 in the fetal liver and the maternal serum were 23.9 and 27.0%, respectively, in normal pregnancies, and 28.7 and 38.5%, respectively, in pregnancies with a trisomy 21 fetus. There was no statistically significant difference between the percentage in the fetal liver and the percentage in the maternal serum in normal pregnancies; however, a significant difference (P < 0.01) was found in pregnancies with a trisomy 21 fetus. In regard to the percentage of AFP-L3 in the fetal liver, there was no significant difference; however, a significant difference (P < 0.05) was found in the maternal serum between normal pregnancies and pregnancies with a trisomy 21 fetus.

CONCLUSIONS

The transference of the AFP-L3 fraction might be relatively high in the placentas of women carrying a trisomy 21 fetus, and this could be the one of the reasons for the increase in the percentage of AFP-L3 in the maternal serum in pregnancies with a trisomy 21 fetus.

Blood-based screening and light based imaging for the early detection and monitoring of ovarian cancer xenografts

We report a novel technology for in vivo early detection, identification, and monitoring of ovarian cancer in live mice leading to better treatment outcome. A genetic dualistic reporter system that uses an adenoviral (Ad) vector to transfer the genetic reporters to the ovarian cancer is described. Infection of the cancer cells leads to expression of one reporter that is detected in blood, namely, secreted human placental alkaline phosphatase (SEAP). A second reporter, namely, enhanced green fluorescent protein (GFP) is also delivered by the Ad, leading to expression at the site of ovarian cancer. The SEAP gene under control of the cytomegalovirus (CMV) promoter element is linked to the GFP gene with an IRES element. A diagnostic adenoviral vector (Ad) encoding the SEAP and GFP (Ad5-SEAP-GFP) is produced. Efficacy of newly developed diagnostic vector is tested in cell culture and animal models. SKOV3ip.1 cells are infected with Ad5-SEAP-GFP. Over time the cells are monitored for fluorescence and SEAP is also measured in the growth media supernatant. For animal experiments, SKOV3ip.1 cells are implanted first in nude mice either subcutaneously (SC) or intraperitoneally (IP) separately. After 4-7 days, the Ad5-SEAP-GFP is administered. Control mice do not receive any Ad vector. All mice are imaged with a fluorescent stereomicroscope after 24 h, and blood is collected for SEAP analyses. Increasing green fluorescence is detected in all SKOV3ip.1 cells infected with Ad5-SEAP-GFP, while SEAP levels in growth media increase over monitoring period. Expression of GFP in both SC and IP tumors is detected by 24 h in the live mice. At this time, the SEAP blood levels are more than 2-3 fold greater than blood levels of control group. GFP fluorescence and SEAP levels continue to increase in all mice that are injected with Ad5-SEAP-GFP until termination. Control mice (both SC and IP) do not express GFP or SEAP throughout the experiment. GFP contrast is necessary to differentiate between micro-sized early stage non-palpable ovarian tumor nodules and surrounding normal tissue. While the studies are conducted in mice, it is envisioned that the dual-based approach will eventually be translated into human applications for routine diagnosis and monitoring of ovarian cancer when an ovarian cancer specific promoter will be available. Due to the thickness of the abdominal wall in human laparoscopy or laparotomy will be necessary. This system will provide gynecologic oncologists with a more effective tool for treating patients. The blood-based screening assay provides a quick test to determine the presence of the ovarian cancer at its earliest stage. The location of the ovarian cancer is afforded by the light-based imaging component, which represents a new and improving technology with tremendous advantages of sensitivity and spatial resolution to localize micro-sized tumor nodules. The novelty of the dualistic system is the linkage of blood-based reporter screening as a selection criteria for subsequent light-based imaging procedures. This combination will lead to an accurate and widely applicable method for the early detection and monitoring of ovarian cancer, especially in high-risk women

Multiple advantages of alpha-fetoprotein as a marker for in vivo gene transfer

The development of improved gene transfer vectors has been hampered by the lack of a nonimmunogenic reporter gene that can be serially quantified in the serum or from other sites. In response to the need to develop a new reporter protein, we have evaluated alpha-fetoprotein (AFP) as a potential candidate. A first-generation E1/E3-deleted adenoviral vector expressing human AFP (hAFP) was generated as a preliminary tool to evaluate AFP as a reporter. Using both mouse and baboon models, hAFP expression was evaluated in serum after intravenous delivery and in serum and bronchioalveolar lavage (BAL) fluid after delivery to the lung. In immunocompetent animals, intravenous delivery of the hAFP adenoviral vector resulted in hAFP expression in the serum early after injection, which declined rapidly over time. Disappearance of hAFP from the serum was complete by 3-4 weeks after administration and was accompanied by robust antibody responses to hAFP and loss of infected cells. After lung delivery, hAFP could be detected in both serum and BAL. This allowed the analysis of the kinetics of gene expression in the lung without sacrificing the animals. In both liver and lung, immunohistochemical analysis correlated well with hAFP levels as detected in serum or BAL, indicating that serum levels were a reliable marker of tissue expression. Preliminary results with a mouse AFP expressed in a helper-dependent adenoviral vector indicate that use of a species-specific version of AFP will eliminate the complication of antibody development. These initial evaluations suggest that AFP is useful as a reporter gene to evaluate gene expression of therapeutic cassettes in multiple tissues, and it should be considered for use in human subjects.

Immuno-suppressive effect of human alphafetoprotein: a cross species study

Alphafetoprotein (AFP) is the major serum protein of fetal life in human and other mammalian species. The phylogenetical conservatism of AFP demonstrated by extensive immunological cross reaction between human AFP and AFP of a number of species, suggest that AFP plays a general role in the successful pregnancy of all mammalian species. The present work clearly demonstrates the antiproliferative effect of human AFP on lymphocytes, harvested from normal human donors. The inhibitory effect of human AFP is quite significant in the same dose during blastic transformations of the lymphocytes. In this study, peripheral blood mononuclear cells were induced to blastic transformations with phytohaemagglutinin (PHA-M) and the effect of AFP was quantified by the incorporation of [3H]-thymidine into newly synthesized DNA during 24 hrs pulse. Moreover, human AFP shows similar immuno-suppressive effect to other species of lymphocytes also. In all the three species (mouse, rat and hamster) studied, a parallelism was noted in their respective percentage of thymidine incorporation values at the comparable doses. These results establish a cross species inhibitory effect of human AFP and it may be stated that this effect is directly targeted on T-helper cells and has no interaction with interleukin-2 (IL-2).

Biphasic reduction and concanavalin A binding properties of serum alpha-fetoprotein in preterm and term infants

Reference values for postnatal serum alpha-fetoprotein (AFP) and concanavalin A (ConA) binding subfractions of AFP in preterm and term infants are presented. Preterm infants had 10-fold higher serum concentrations of AFP than did term infants at birth. The reduction of serum values of AFP was biphasic in both groups and differed significantly between the two groups. The first declining phase continued for approximately 4 months in preterm and for 2 months in term infants, and was related to the degree of prematurity. The AFP values reached adult levels by 12 months in preterm and by 9 months in term infants. The developmental pattern of the carbohydrate moiety of AFP was determined by ConA fractioning. The proportion of the ConA nonreactive subfraction of AFP in preterm and term infants at birth was 6% and 13%, respectively; it increased more rapidly in term than in preterm infants but reached 85% to 95% by the age of 6 months in both infant groups. Our results indicate that the postnatal maturation of AFP synthesis is dependent on gestational age. Malignant recurrences of neonatal sacrococcygeal teratomas were associated with an increase in serum concentration of AFP and a decrease in the proportion of the ConA nonreactive subfraction of AFP.

Maternal serum AFP levels in the first trimester of pregnancy

Maternal serum alphafetoprotein was assayed in 436 women presenting for termination of pregnancy at 6 to 12 weeks. The normal range for each week is presented. There was a progressive rise of AFP levels from week 7 onwards, but a clear separation from non-pregnant values was only apparent after 8 weeks. The definition of a 'low normal' range for the identification of cases at risk of Down's syndrome will probably only be possible at 11 weeks or later.

Rise in maternal serum alpha-fetoprotein concentration after chorionic villus sampling and the possibility of isoimmunization

Maternal serum alpha-fetoprotein concentrations were determined by radioimmunoassay in 72 patients immediately before and after chorionic villus sampling for prenatal diagnosis. Fifty percent showed a rise of greater than or equal to 5 ng/ml. Assuming such rises represent fetal blood crossing the intervillous space, in 14% of the cases greater than or equal to 60 microliters of fetal blood was transferred at the time of chorionic villus sampling. A positive correlation was found between the magnitude of rise in maternal serum alpha-fetoprotein levels and the amount of villi removed (r = 0.39, p less than 0.001). When cases were examined by number of passes, a greater rise in maternal serum alpha-fetoprotein levels was noted with multiple passes than with single passes for a given sample size. The transfer of greater than or equal to 60 microliters of fetal blood suggests that maternal sensitization to fetal antigens may occur after chorionic villus sampling. During biopsy, as small a sample of villi as necessary for diagnosis should be taken with as few catheter passes as possible.

Evaluation of serum CA125 values in healthy individuals and pregnant women

CA125 is an antigenic determinant associated with human epithelial ovarian carcinoma. This study was undertaken to evaluate the distribution of serum CA125 levels and the effect of smoking on these levels among healthy individuals and clarify the relation of maternal serum CA125 level and pregnancy. Among 552 healthy individuals, the distribution of serum CA125 values was demonstrated to resemble logarithmic normal distribution. Analysis of variance about age and sex revealed apparent elevation of values for women under 49 years of age in comparison with those for women over 50 years of age and men. Values for these two groups were 143 units/ml for the former and 32 units/ml for the latter, with a 99.7% confidence limit. These values exclude 99.3% of the former and 99.7% of the latter. Serum CA125 values were not affected by smoking. The measurement of serum CA125 levels in 71 pregnant women disclosed a significant elevation during the first trimester in comparison with nonpregnant women under 49 years of age. These results indicate that CA125 values must be deliberatively evaluated in young women, especially during first trimester of pregnancy.

Mechanisms of fetal demise in pregnant mice immunized to murine alpha-fetoprotein

Nya: NYLAR mice were immunized to murine alpha-fetoprotein (AFP) by active immunization with rat AFP in Freund's adjuvant emulsion before mating or by passive immunization with a high or low dose of whole rabbit antimouse AFP serum or rabbit anti-AFP IgG at 8-20 days of gestation. In the passively immunized group, anti-AFP serum or purified anti-AFP IgG administered at the end of the second week of gestation produced abortion after 24 hours of 41 and 48% of fetuses, respectively. Although abortion did not occur in the low-dose group, the anti-AFP serum produced fetal death in 32%, as did anti-AFP IgG in 26%, in 72 hours. In the actively immunized group rat AFP produced developmental arrest, but not abortion, in mothers bearing autologous antibodies to mouse AFP. Histopathologic analysis revealed that fetal death resulted from separation of fetal and maternal tissues of the placenta due to subplacental hemorrhages. Immunofluorescent localization of the rabbit IgG implicated both the chorioallontois and yolk sac placenta as target tissues.

A comparison of acid-elution techniques and alpha-fetoprotein levels for the detection of fetomaternal bleeding

Practical and reliable methods to identify and/or quantitate fetal blood are becoming more important in the modern practice of obstetrics. In this study, two commercially available acid-elution techniques were compared with plasma -alpha-fetoprotein (AFP) by simultaneously testing samples of fetal blood mixed with adult blood in fixed ratios. Thirty-one samples representing a range of amounts of fetomaternal hemorrhage, from 0.024 to 48 ml, were analyzed. The acid-elution techniques were equally effective in detecting fetomaternal hemorrhage greater than 15 ml, but the bmc Reagent set was the most accurate for detection of small numbers of fetal erythrocytes. The accuracy of AFP was greater than that of either acid-elution technique, but its clinical usefulness is limited by the necessity for a prehemorrhage sample.

Alpha-fetoprotein: a review

Alpha fetoprotein (AFP) is the major protein of fetal serum and most resembles albumen, which replaces it shortly after birth. It is produced by fetal liver and passes into the amniotic fluid (AF) via fetal urine. A small amount crosses the membranes into the maternal circulation. Excluding fetal blood contamination, elevated AF/AFP levels indicate fetal demise or one of several abnormalities. Maternal serum (MS) AFP measurement can be used as a screening procedure to identify neural tube defects providing a rigorous protocol is followed. This requires that a laboratory establish its normal range of MS/AFP levels between 15 and 20 weeks gestation, employ a reliable assay with adequate controls, and has recourse to genetic counseling as well as expert sonography, amniocentesis and amniography if necessary. Pregnancy is the only normal situation in which AFP is present after birth. It may be present in high levels in certain malignancies and has been useful in monitoring their recurrence. This article will review the history, biochemistry, and different assays of AFP in AF and blood as well as the indications and limitations for their use.

Direct analysis of the lectin reactivity of alpha-fetoprotein in maternal serum by crossed affinity radio-immunoelectrophoresis

Affinity experiments with the lentil (Lens culinaris) lectin have revealed the existence of two distinct molecular populations of alpha-fetoprotein: lectin reactive and lectin non-reactive. Using a combination of crossed lectin immunoelectrophoresis and radio-immunoelectrophoresis, it has been possible to obtain directly the lentil lectin affinity patterns of alpha-fetoprotein present in maternal sera. The lentil lectin reactivity of maternal alpha-fetoprotein decreases almost linearly with the gestational age from week 15 to 35.

Maternal plasma, human placental lactogen, alpha-fetoprotein, prolactin and growth hormone in early pregnancy

Human placental lactogen (HPL), alpha-fetoprotein, prolactin and growth hormones were assayed simultaneously twice weekly in 21 women from 4--16 weeks' gestation. Mean levels were established from 15 of the women for comparison with one woman with a twin pregnancy, two who aborted and three who received progestogen supplements. There was wide interpatient variation in all hormone levels excepting HPL. The mean levels of all except growth hormone showed an upward trend. Mean growth hormone levels were higher initially but remained within a 2--4 ng/ml range throughout. In the twin pregnancy, only HPL and alpha-fetoprotein levels were significantly raised. HPL was detected in one of the two women who aborted, whereas growth hormone was initially extremely high, falling precipitously prior to abortion in both women. Treatment with progestogen supplements did not appear to influence any of the hormones measured. This study suggests that serial estimations of HPL appear to be the most cost-effective guide to early fetal well-being of the four hormones measured.

Alpha fetoprotein levels in neonatal hyperbilirubinaemia

Serum alpha fetoprotein (AFP) levels were studied in 15 neonatally hyperbilirubinaemic children and 15 controls matched for sex and gestational age. All children were born between 38 and 40 weeks of gestation. During the first seven weeks of postnatal life hyperbilirubinaemic children had serum AFP concentrations over twice as high as controls. At the age of 5-7 days the mean (+/- S.E.M.) serum AFP values were 52.4 +/- 5.8 mg/l for hyperbilirubinaemic children and 24.8 +/- 4.3 mg/l for controls (p less than 0.001). At 20-25 days of age they were 7.28 +/- 1.10 and 2.75 +/- 0.45 mg/l, respectively (p less than 0.001), and at 40-49 days 1.39 +/- 0.21 and 0.46 +/- 0.07 mg/l (p less than 0.001). However, no correlation was found between serum bilirubin and AFP concentrations in hyperbilirubinaemic children.

A comparison of maternal serum levels of alpha-fetoprotein in normal and pre-eclamptic pregnancies

Alpha-fetoprotein (AFP) concentrations were measured by radioimmunoassay in serum from women with normal and pre-eclamptic pregnancies. An analysis of the results obtained in normal pregnancy was made using arithmetic and semi-logarithmic scales, and a statistical conversion of the AFP values in relation to gestational age was introduced to allow an easier interpretation of results. In pre-eclampsia, significantly lower mean AFP values were obtained, with the majority of individual values being lower than the mean for normal pregnancy. These low levels were not associated with fetal death, but appeared to be related to the severity of disease. The significance of these findings remains to be evaluated.

Neural tube defects: maternal serum screening and prenatal diagnosis

Neural tube defects represent some of the most common and serious of the congenital malformations. Although elevation of alpha-fetoprotein in amniotic fluid is not diagnostic, it does indicate an abnormality of the fetus in a very high proportion of cases. A normal level, however, does not exclude the possibility of a closed neural tube defect. It is therefore recommended that all amniocenteses performed between 15 and 20 weeks of gestation include measurement of alpha-fetoprotein. Maternal serum alpha-fetoprotein assay is a screening test and pilot studies will be necessary to determine its value as a routine prenatal blood test.

Immunochemical properties of alpha-fetoprotein (AFP) and antibodies to autologous AFP

Alpha-fetoprotein (AFP) is a strong immunogen when injected into another species, but does not elicit an immune response in the species of origin of the AFP. AFPs from different mammalian species are crossreactive. AFP and albumin show sequence homology. They do not crossreact in their native state, but their unfolded (reduced and carboxamidomethylated) forms are immunologically crossreactive. Antibodies to autologous AFP can be induced in animals by immunization with heterologous or modified homologous AFP. These antibodies eliminate the AFP normally measurable in the serum and delay the elevation of serum AFP caused by hepatomas, but do not protect against such tumors.

The effect of heterologous antisera on embryonic development. XIII. Lack of effect of antisera to alpha fetoprotein

This investigation was carried out to determine whether heterologous antisera to alpha fetoprotein (AFP) are embryotoxic to developing rat embryos. Homogeneous rat AFP was isolated and antisera directed against this glycoprotein were produced in rabbits, horse and goat. The effect of the antisera on embryonic development was examined by injecting the antisera intraperitoneally into pregnant rats on the ninth, eleventh and thirteenth days of gestation. The results demonstrated that there was no evidence of increased incidence of fetal abnormalities in 472 surviving fetuses of 42 injected rats. There was no evidence of increase embryonic death or retardation of intrauterine growth following administration of the antisera on the ninth, eleventh and thirteenth days of gestation. The localization of the injected antisera was examined by the indirect immunofluorescent method. The results showed that the heterologous AFP antibodies localized specifically in the visceral yolk sac placenta. No antibody localization was observed in the embryo proper or the chorioallantoic placenta. It is speculated that the localization of AFP antibodies in the visceral yolk sac does not interfere with the embryotrophic function of the visceral yolk sac placenta.

False positive amniotic fluid alpha fetoprotein levels resulting from contamination with fetal blood: results of an experiment

The finding of an elevated level of alpha fetoprotein (AFP) in amniotic fluid is of value in the prenatal diagnosis of open neural tube defects. The present study was done to determine the amount of fetal blood required in amniotic fluid to produce a significant and misleading increase in AFP. Fetal blood was obtained at hysterotomy, and measured volumes were added to amniotic fluid samples. Bethe-Kleihauer tests, red cell counts, and AFP determinations were done. On the average, at 16 weeks' gestation, contamination of 5 ml. of amniotic fluid with 22 mul of fetal blood will results in an increase in AFP of 1.6 mg. per deciliter. Fetal cells in a much lower concentration can readily be detected by the Bethe-Kleihauer technique. A Bethe-Kleihauer test and red cell count should be done on all blood-stained amniotic fluid samples to determine the amount of fetal blood present. The contribution of the fetal blood AFP can then be estimated and must be considered in the interpretation of the total amniotic fluid AFP result.

Serum alpha-fetoprotein in adults, in women during pregnancy, in children at birth, and during the first week of life: a sex difference

In order to investigate whether a sex difference exists in alpha-fetoprotein serum concentration, blood samples were collected from 133 adult men, 52 adult women, 239 pregnant women at different ages of gestation, 16 girls and 18 boys at birth, and seven girls and seven boys during the first week of life. In the case of 15 boys and 10 girls, blood samples were also collected from their mothers at the time of delivery. Serum AFP was measured by a radioimmunoassay method. In all neonates the mean value was 625 times higher than in all mothers at the time of delivery and 13,000 times higher than in adults. No difference was found between mothers of girls and those of boys both during pregnancy and at the time of delivery. However, at birth, the fetal AFP serum concentration was 1.8 (p less than 0.001) times higher in boys than in girls. This sex difference was maintained during the first week of life. The half-life of serum AFP was 5 to 6 days in the neonate. The origin and the possible physiologic significance of such sex difference in AFP deserve further investigations.

Toxemia of pregnancy: assessment of fetal distress by urinary estriol and circulating human placental lactogen and alpha-fetoprotein levels

The efficacy of three biochemical methods for the detection of fetal distress was assessed in a prospective study of 224 singleton pregnancies complicated by toxemia. Fetal distress was diagnosed in 65 cases (29 per cent). Abnormally low urinary estriol (E3) excretion pointed out 63 per cent, low serum levels of human placental lactogen (HPL) 27 per cent, and elevated maternal serum alpha fetoprotein (AFP) 10 per cent of distressed fetuses. The efficacy of each test increased with the severity of maternal disease. The frequencies of false pathologic levels were: E3 19 per cent, HPL 0 per cent, and AFP 1 per cent of the cases with a normal fetal outcome. Although E3 was by far the most effective marker, abnormal levels of HPL and AFP provided supportive evidence for fetal distress by pointing out those cases in which E3 reading was not a false positive.

Alpha fetoprotein in the antenatal diagnosis of the congenital nephrotic syndrome

In the congenital nephrotic syndrome (Finnish type), concentrations of alpha fetoprotein in the amniotic fluid and maternal serum are markedly elevated in the second trimester of pregancncy. Demonstration of this alteration allows early prenatal diagnosis of this fatal condition and elective termination of the pregnancy before 20 week's gestation.

Serum alpha1-fetoprotein in cystic fibrosis

In 38 children and adolescents with cystic fibrosis, in 19 normal children and 62 healthy adults the serum alpha1-fetoprotein concentrations were measured by radioimmunoassay. In cystic fibrosis patients 97.5% and in normal children 95% of the alpha1-fetoprotein values were within the normal range for healthy adults (1--9 ng/ml). Critical judgement of the reported findings in literature and our own results demonstrate that the investigation of alpha1-fetoprotein in the serum cannot serve for detecting homozygotes of cystic fibrosis genes or heterozygote carriers.

Alpha-fetoprotein

Despite all the information about AFP presented, a great deal still needs to be discovered especially in pregnancy. Geographical and racial differences remain to be elucidated. Similarly, differences in obstetric population in Helsinki and Baltimore, for example, are only now being studied. Sex differences may exist; Lardinois and associates195 cited a higher level of AFP in male than female fetuses. The important questions that need to be answered are whether AFP assays can help improve the other half of prenatal care- that directed to the fetus- and whether the AFP model can help enhance our understanding of the similarities and differences of fetal and cancer cells.

Characterization of homologous anti-alpha-fetoprotein antibodies produced in rabbits

The natural tolerance to alpha-fetoprotein (AFP) was broken in rabbits by immunizations with purified AFP from different species and homologous AFP chemically modified by haptenation. Some of the rabbits were boostered with rabbit AFP. The highest titers were obtained with human AFP, which shows a strong cross-reaction with rabbit AFP. The homologous antibodies were of lower avidity than heterologous (sheep) antisera. Injections with rabbit AFP did not alter the avidity or titer. All antibodies produced by injections with human AFP could be absorbed with the original immunogen, and no reactivity against determinants unique to rabbit AFP could be found. These results indicate that the antibody activity against autologous AFP is based on cross-reactivity and that the immunizations did not make the autologous AFP immunogenic. These findings may be important in view of the possible use of AFP as a target antigen in tumor immunotherapy.

[Variations of the concentrations of certain glycoproteins in maternal serum, fetal serum and amniotic fluid during pregnancy (author's transl)]

The authors investigated systematically the variations during normal pregnancies of the concentrations of alpha-1-antitrypsin, orosomucoid, transferrin and alpha-fetoprotein simultaneously in maternal serum, fetal serum and amniotic fluid. The role of certain factors such as the gestational age birth weight, placental weight and pairty were studied with regard to variations in the concentrations of each of these proteins. This research permitted the definition during pregnancy of the normal concentrations for these four proteins and allowed us to learn more about protein exchanges between fetal blood, maternal blood and amniotic fluid. There exists a difference between the concentrations of alpha-1-antitrypsin and of orosomucoid found for primigravidae and for multigravidae. The role of these glycoproteins in preventing the mother from rejecting the fetus (insofar as the fetus may be considered as an allograft) is discussed.

A rapid method for the purification and radioimmunoassay of human alpha-fetoprotein

Human alpha-fetoprotein (AFP) was isolated from cord serum on an immunoadsorbent column obtained by covalently linking rabbit anti AFP to cyanogen bromide activated Sepharose. Bound AFP was eluted with 8 M urea with better than 50% recovery. The purified AFP was iodinated prior to its use in a double antibody radioimmunoassay. The purification and radioimmunoassay employ commercially available materials. A standard inhibition curve was obtained which allowed determination of AFP levels between 50 and 100 ng/ml in human serum. The assay was verified by measureing AFP levels in normal female serum, pregnancy serum, cord serum, hepatoma ascitic fluid and a standardized AFP solution.

Maternal plasma alphafetoprotein levels in the second half of normal pregnancy: relationship to fetal weight, and maternal age and parity

A semi-automated radioimmunoassay for plasma alphafetoprotein has been developed, suitable for routine clinical use. Several hundred samples can be assayed in a working week, with results available within 24 hours. The use of extensive quality controls ensures that good precision is maintained both within and between assays. The range of plasma concentrations of alphafetoprotein in the second half of pregnancy has been established in 100 normal subjects. The levels rise progressively to reach a peak at 32 weeks, and thereafter fall until term. No relationship between circulating alphafetoprotein levels and birth weight was observed.