Immunoadsorbent isolation of pregnancy-specific beta 1-glycoprotein from maternal serum

A three-step procedure for the purification of pregnancy-specific beta 1-glycoprotein (PS beta 1G) on a milligram scale from maternal serum has been developed. The principal purification was achieved by the use of an immunoadsorbent and the remaining impurities were removed by hydroxylapatite chromatography and negative affinity chromatography. The overall procedure resulted in the purification of approximately 10 mg of PS beta 1G which represented about 21% of PS beta 1G in 300 mL, of serum. The PS beta 1G was of high purity as shown by analytical polyacrylamide gel electrophoresis, sodium dodecyl sulfate--polyacrylamide gel electrophoresis, and immunochemical tests. Experiments by immunoelectrophoresis and gel chromatography indicate that the electrophoretic mobility and relative mass of the purified PS beta 1G are very similar to those of the native serum protein. Structural analysis of PS beta 1G suggests that it is composed of two identical subunit chains bonded noncovalently. However, a trimeric structure for PS beta 1G cannot be ruled out based on the uncertainty of relative mass estimates by gel chromatography in nondenaturing solvent. The anomalous characteristics of a previous purified polymeric form of PS beta 1G (PS beta 1G-I) are discussed in relation to the new findings presented here.

[Isolation from a pregnant woman of a serum protein responsible for inhibiting an in vitro cytotoxicity reaction]

A non specific immunosupressive factor able to block an in vitro cytotoxicity reaction is demonstrated in the serum of pregnant women. A solution containing this blocking factor is obtained by gel filtration and precipitation of plasma by polyethylene glycol 4 000. Then after immunisation of rabbits the immune serum can be used for affinity chromatography. An alpha 2 glycoprotein has been separated which inhibits the in vitro cytotoxicity reaction and whose molecular weight determined by gel filtration and polyacrylamide gel is about 200 000 daltons.

Immunochemical demonstration of a new pregnancy protein in the mare

An antiserum against the serum of a pregnant mare was absorbed with stallion serum. This antiserum then gave two precipitates in crossed immunoelectrophoresis with serum from pregnant mares as the antigen. The two precipitates exhibited beta-1 and alpha-2 electrophoretic mobility. Identity was demonstrated between the alpha-2 mobile protein and PMSG. The absorbed antiserum inhibited the biological action of the PMSG preparation when tested in mouse ovarian weight assays. The beta-1 mobile protein was not detected in the serum from non-pregnant mares, stallions or geldings and was detected earlier in pregnancy (Day 30) than was PMSG (Day 42).

Molecular heterogeneity of pregnancy-specific beta 1-glycoprotein (SP1)

Ion-exchange chromatography has been used to isolate three separate forms of Pregnancy-Specific beta 1-Glycoprotein (SP1) from pooled, late-pregnancy human sera. Each of the three components was immunochemically identifiable as SP1, yet distinguishable from each other on the basis of rocket morphology resulting from rocket immunoelectrophoresis (RIE). The elution profile from DEAE Sephacel indicated that each component has an isoelectric point below pH 8.6, but suggested a different charge for each molecular species. Crossed immunoelectrophoresis (XIE) of pooled, late pregnancy serum suggested the presence of each component prior to physico-chemical treatment and showed the components to be characterised by alpha, beta or gamma electrophoretic mobility. The differences in rocket morphology suggested differing affinities for the antiserum, and a difference in molecular size, which was confirmed by gel filtration.

Detection and partial characterization of two bovine pregnancy-specific proteins

Two pregnancy-specific proteins were detected by immunoelectrophoresis using antisera developed to homogenates of bovine extraembryonic membranes. Antisera also reacted to extracts of endometrium from pregnant cows and extraembryonic fluids. However, antisera did not react with a preparation presumed to be bovine placental lactogen, fetuin, extracts of various somatic tissues from pregnant cows or extracts of endometrium from nonpregnant cows. One of the proteins had an estimated molecular weight of 65,000-70,000, an isoelectric point of 4.6-4.8 and yielded a reaction of identity with bovine alpha 1-fetoprotein by immunodiffusion. The second protein yielded a reaction of identity with bovine alpha 1-fetoprotein by immunodiffusion. The second protein had no immunological cross-reactivity with the known proteins or organ extracts which were tested. The molecular weight and isoelectric point was 47,000-53,000 and 4.0-4.4, respectively. These data demonstrate the presence of at least 2 pregnancy-specific proteins in cattle.

Heterogeneity of the pregnancy-specific beta 1-glycoprotein (SP1)

The pregnancy-specific beta 1-glycoprotein (SP1) in pregnant serum fractionated by ammonium sulfate precipitation and anion exchange chromatography was investigated by various electrophoretic methods. From these investigations it appears that in addition to the major component SP1(beta) three other components are present, termed SP1(gamma), SP1 (alpha 2(2)) and SP1 (alpha 2(1) on the basis of their electrophoretic mobilities. The isoelectric point (pI), estimated by isoelectric focusing, and the relative molecular mass (Mr), estimated by Sephadex G-200 gel filtration chromatography are for SP1(gamma): pI 2.9--4.9, Mr approximately 80000; SP1(beta): pI 2.5--4.5, Mr approximately 80000; SP1(alpha 2(2)): pI less than or equal to 6, Mr greater than or equal to 200000; SP1(alpha 2(1)): pI less than 3, Mr approximately 30000. Based on the interaction with phenyl-Sepharose and concanavalin A all four species of SP1 are amphiphilic glycoproteins.

Extracts of pregnancy urine contain a mitogen for human peripheral blood lymphocytes (PBL)

A mitogen for human peripheral blood lymphocytes (PBL) has been found in commercial batches of crude human chorionic gonadotropin (hCG), which is obtained from pregnancy urine. These crude hCG preparations, as well as column eluates free of hCG and a previously noted immunosuppressive factor, are mitogen for normal human PBL cultured in fetal calf serum. This mitogen is designated pregnancy-associated growth factor (PAGF) because of its source. PAGF induces 3H-thymidine incorporation of mixed Ia+ non-T cells and T cells, probably confined to the helper subclass; proliferation is abolished by complement-mediated lysis using monoclonal antisera to Ia, mature T cells (OKT3), and the Th (OKT4) subset, but not by antisera to the Ts (OKT8) subset. The proliferating cell is a T cell because irradiation of these cells, but not the non-T cells, abolished PAGF mitogenicity. In addition, PAGF augments the autologus mixed lymphocyte reaction. Preliminary experiments indicate that its m.w., in the range of 18,000 to 22,000, is different from epidermal growth factor, the only previously described growth factor found in crude hCG preparations. In addition epidermal growth factor failed to stimulate PBL under similar conditions.

Identification and characterization of a calcium-binding protein from human placenta

The human placenta has been found to contain a specific calcium-binding protein (HCaBP) which increases in amount as a function of gestation. A procedure is described for the purification of the HCaBP to chromatographic and electrophoretic homogeneity. The HCaBP is (a) a high molecular weight protein with a native Mr of 150 000 and appears to be a dimer of subunits of Mr = 70 000; and (b) an acidic protein with a pI of 4.6. Amino acid analysis of the HCaBP revealed an abundance of acidic amino acid residues (27 per cent = Asp and Glu). A specific antiserum has been prepared against purified HCaBP. With Ouchterlony double immunodiffusion, the HCaBP appears to be specific for the human placenta, and is not cross-immunoreactive with the CaBP of the chick embryonic chorio-allantoic membrane.

Purification of placental anemia inducing factor (PAIF) and its clinical application by radioimmunoassay

Human Placental Anemia Inducing Factor (PAIF) was purified from crude placental preparation called P- 62, which had common biological and immunological natures with the same preparation from gastric juice, gastric tissues, serum and urine of patients with malignant neoplasma, especially gastric cancer. The obtained PAIF was homogeneous on polyacrylamide gel electrophoresis and gave a specific band in the region of gamma-A and/or gamma-M globulin on immunoelectrophoresis. The purified PAIF induced anemia in rabbits by intravenous administration at a dose of 2.7 micrograms/Kg of body weight. No cross antigenicity of PAIF was observed with alpha-Fetoprotein. HBs antigen and CEA. Serum AIF of patients was measured using PAIF as a standard by radioimmunoassay. AIF levels in sera of patients with malignant neoplasma were significant high compared with those of control groups.

Observations on the separation of SP1 alpha and SP1 beta by affinity chromatography

SP1 antigens in late pregnancy blood, in placental extracts and in acidified plasma have been purified on positive affinity chromatography columns with immobilized SP1 antiserum and on negative affinity columns with immobilized antihuman non-pregnancy serum. Both SP1 alpha and SP1 beta are bound by the positive column but only SP1 alpha is bound by the negative column. This is adduced as further support for the view that SP1 alpha is formed by the combination of SP1 beta with a protein present in non-pregnancy serum.

Purification of pregnancy-associated plasma protein-A by a two step affinity chromatographic procedure

A high molecular weight pregnancy specific protein (PAPP-A) was purified by immunospecific affinity chromatography. The purification procedure was based on a new method for affinity chromatography using direct coupling of precipitable immune complexes to the gel matrix. The procedure was performed in two steps: a positive immunospecific affinity chromatography followed by a negative affinity chromatography in which balanced amounts of anti-contaminant antibodies were used as ligant. The purified material at a concentration of 300 microgram/ml was tested by immunoelectrophoretic methods and no contaminants were detectable. WHO beta-1 SP1 reference material 78610 contained 45 microgram PAPP-A/ml.

Separation of two pregnancy-associated proteins with SP1 determinants and the conversion of SP1 beta to SP1 alpha

The alpha and beta forms of the pregnancy-associated protein, SP1 which have been previously identified in late pregnancy serum were found to be also present in the placenta. The alpha form was somewhat more difficult to extract, requiring the use of detergents in the extracting buffer. The two variants can be separated by ion exchange chromatography or by gel filtration and distinguished by the different shapes of the precipitation rockets on immunoelectrophoresis. The alpha variant appears to be the larger molecule on gel filtration. When solutions of SP1 are acidified to pH 2.5 the beta form is rapidly converted to the alpha form and the latter is slowly destroyed. It is suggested that SP1 alpha represents the combination of SP1 beta with some other protein present in the placenta and in the serum.

[New placental protein (PP15) with immunosuppressive properties (author's transl)]

The isolation and characterization of a new placental protein (PP15) which has immunosuppressive properties are described. The protein was purified from extracts of human term placentae by rivanol and ammonium sulfate fractionation, gel filtration, ion exchange chromatography, preparative zone electrophoresis, and chromatography on hydroxyapatite. PP15 was found to have a sedimentation coèfficient of 2.9 S and a molecular weight of 30,700 daltons as determined by ultracentrifugation; its molecules apparently are composed of two identical subunits which are held together by non-covalent bonds. The electrophorectic mobility of PP15 corresponds to that of albumin. PP15 is a glycoprotein and contains 3.3% carbohydrates (hexoses 2.8%, hexosamines 0.3%, sialic acid 0.2%). The amino acid composition of this protein was also determined: the most abundant amino acids in the peptide chain were found to be glutamic acid, aspartic acid, isoleucine, and leucine. PP15 has immunosuprressive properties: on testing its effect on the lymphoycte transformation in the MLC-test in vitro a significant inhibitory activity could be demonstrated.

Studies on human pregnancy-associated plasma protein A. Purification by affinity chromatography and structural comparisons with alpha 2-macroglobulin

Pregnancy-associated plasma protein-A (PAPP-A) has been purified by a combination of methods including antibody-affinity chromatography. The resultant protein, obtained in 16% yield from maternal serum, appeared as a single major component on non-denaturing polyacrylamide and SDS/polyacrylamide gel electrophoresis. The protein showed a single component when analysed by isoelectric focusing under denaturing conditions in the presence and absence of reduction and had a pI of 4.34 and 4.42 respectively. These pI values were indistinguishable from those of alpha 2-macroglobulin (alpha 2M). The molecular weight of the PAPP-A polypeptide as shown by SDS/polyacrylamide-gel electrophoresis was 187000, with a minor component of mol.wt. 82500 that was attributed to proteolysis. Since native PAPP-A had a molecular weight on gel chromatography very similar to that of alpha 2M (620000--820000), it was concluded that PAPP-A was a homotetramer. In the absence of reduction, a high-molecular-weight (420000) protomer of PAPP-A was found. It was deduced that PAPP-A, like alpha 2M, is a dinner, whose protomers are composed of disulphide-linked polypeptide chains. It was found that the molecular weight of the PAPP-A polypeptide exceeded that of alpha 2M by 3.3%, but that the total carbohydrate content of PAPP-A exceeded that of alpha 2M by 10% and that its neutral carbohydrate content exceeded that of alpha 2M by between 7.4 and 9.0%. The significance of the estimated molecular weights of alpha 2M (181000) and its major tryptic fragments is discussed in the light of published values. A tryptic fragment alpha 2M (82500 mol.wt.) was apparently the same size as the major tryptic fragment of PAPP-A.

The role of lysine-41 of ribonuclease A in the interaction with RNase inhibitor from human placenta

3-N-Carboxymethyl-His-12 and 1-N-carboxymethyl-His-119-RNase A bind to the naturally occurring RNase inhibitor, isolated from human placenta, 1.3 and 3.6 times, respectively, more strongly than does native RNase A. Near-ultraviolet circular dichroism measurements indicate that the conformational change which occurs upon carboxymethylation of either of the active site histidine residues appears different from that which the protein undergoes upon binding of substrate of a substrate analogue. Specific carboxymethylation of Lys-41 of RNase A decreased the strength of the interaction between the enzyme and the RNase inhibitor to about 12% of the initial value. The near-UV CD spectra of Cm-Lys-41-RNase A and of acetimidyl-RNase A (9.3 lysines modified) and carbamylated RNase A (3.0 lysines modified), which also have weaker interactions with RNase inhibitor of 25% and 10%, respectively, show a negative [theta]MRW identical to that of native RNase A at 275 nm but are altered in the positive [theta]MRW at 240 nm. The CD measurements suggest that one or more tyrosine residues of RNase A may be involved in the interaction with inhibitor. The effects of pH and salt concentration suggest that a major part of the protein-protein interaction is probably through nonpolar forces. The strengths of interactions between the inhibitor and pancreatic RNases from several species were very similar. Since Tyr-92 is the only tyrosine residue retained in all of the species studied, this residue may have a key role in the nonpolar interaction. The data presented herein suggest that the interaction between RNase A and the inhibitor involves the positively charged epsilon-NH2 group of Lys-41 of RNase A. This interaction could result in the inactivation of the enzyme.

Purification of an anemia-inducing factor from human placenta and its application to diagnosis of malignant neoplasms

An anemia-inducing substance was isolated from the human placenta and designated placental anemia-inducing factor (PAIF). An amount of 2.8 mg was purified from about 70 total placentas (total wet weight, 42 kg). PAIF caused hemolysis of human erythrocytes in vitro and reduced the number of erythrocytes in rabbits to 80% of that in the control by i.v. administration of 27 micrograms/kg of body weight. PAIF is a glycoprotein with a molecular weight of about 20,000 and containing about 56% sugar. Radioimmunoassay using 125I-labeled PAIF and antiserum revealed a common antigenicity with crude anemia-inducing substance in sera from patients with cancer. No cross-reactions were observed between PAIF and alpha-fetoprotein, carcinoembryonic antigen, Australia antigen, human chorionic gonadotropin, or human placental lactogen. The level of anemia-inducing factor in normal serum was less than 100 ng/ml, whereas 43 of 63 cancer patients (68.3%) had over 100 ng/ml of serum anemia-inducing factor. Anemia-inducing factor assay may provide a means of detection and aid in the treatment of malignant diseases.

Purification and characterization of pregnancy associated plasma protein A (PAPP-A)

Pregnancy Associated Plasma Protein A (PAPP-A) has been isolated from late pregnancy plasma using ammonium sulphate precipitation, ion exchange chromatography, affinity chromatography on Concanavalin-A, gel filtration and negative affinity chromatography. It was found that PAPP-A is an alpha 2-glycoprotein of 750-820 000 MW, probably a dimer with each monomer being composed of 2 polypeptide chains of 218 000 MW. The amino acid composition as well as other physicochemical characteristics are similar to human alpha 2-macroglobulin. PAPP-A exhibits in vitro an inhibition of the activity of the complement system, of the caseinolytic activity of plasmin and possibly of the urokinase activation of plasminogen. The hypothesis that PAPP-A plays a role in the regulation of fibrinolysis during pregnancy is put forward.

Purification of riboflavin-binding proteins from bovine plasma and discovery of a pregnancy-specific riboflavin-binding protein

Riboflavin-binding proteins have been purified from bovine plasma using flavinyl agarose beads. At least three major protein bands, migrating in regions assigned to the beta- and gamma-globulins of plasma, are observed by cellulose acetate electrophoresis. These proteins coelute from a calibrated Sephadex G-100 column in the volume corresponding to a molecular weight of approximately 150,000; a small amount of another riboflavin-binding protein (molecular weight approximately 37,000) is also present. Polyacrylamide gel electrophoresis of the proteins, with detection by autoradiography of those having tightly bound [2-14C]riboflavin, reveals one protein band which is present only in preparations from pregnant cows. This protein has been purified to apparent homogeneity by storing the mixture of riboflavin-binding proteins at 8 degrees C for 3 weeks, which precipitates the other, less stable proteins. Hence, bovine plasma, like that of the laying hen, contains a number of riboflavin-binding proteins, one of which correlates with pregnancy.