Identification of a murine pregnancy-associated serum protein (alpha 1-PAP) a female-specific acute-phase reactant

A murine pregnancy-associated protein (alpha 1-PAP) with alpha 1-electrophoretic mobility and an estimated molecular weight of 150 000 was present in serum from pregnant C57BL/10 mice but could not be detected in serum of mature non-pregnant females and males. During pregnancy alpha 1-PAP was first detected on Day 7, rose to maximum levels between Days 12 and 14, and thereafter declined during the remainder of pregnancy and was undetectable by Day 8 post partum. The protein was also detected in the serum of females, but not males, subjected to an inflammatory stimulus. Examination of the alpha 1-PAP levels during an acute-phase response in females demonstrated that the protein behaved as a typical classical acute-phase reactant, although the levels were only 10% of those observed during Days 12 to 14 of pregnancy. alpha 1-PAP therefore appears to represent a hitherto undescribed female-specific acute phase reactant in the mouse.

Humoral immune responses in murine pregnancy. IV. Strain dependency and alloantibody specificity

The relationship between the ability of female inbred mice to produce an anti-paternal humoral immune response to allogeneic multiparity and the genotype of the female and male strains has been investigated. Only three, all H-2b haplotype strains, were 'responder' strains and produced anti-paternal alloantibody which did not exhibit C'-dependent cytotoxicity. 'Non-responder' strains produced no alloantibody in spite of multiple pregnancies with H-2 and non-H-2 incompatible male strains. However, even responder strains did not produce alloantibody with all incompatible male strains. The absence of a response in a responder strain mated with a male strain differing at only the H-2 locus implicated a role for non-H-2 influences. A study of the specificity of pregnancy-induced alloantibody suggested that this represented only a fraction of the total alloantibody population induced by conventional immunization in the same strain combination. It is suggested that in pregnancy only the anti-non-H-2 humoral responses remain similar to those induced by immunization, whereas anti-H-2 humoral responses are either absent or are restricted to a fraction of the total foreign H-2 specificities presented. These observations are discussed in relation to the nature of the immunogenic stimulus in pregnancy and the expression of histocompatibility antigens on the feto-placental unit.

Humoral immune responses in murine pregnancy. III. Relationship between anti-paternal alloantibody levels in maternal serum, placenta and fetus

Studies have been carried out on allogeneically mated pregnant female mice to examine the relationship between the levels of anti-paternal alloantibody occurring free or as soluble immune complexes in the maternal peripheral circulation and that existing in a bound form in the placenta and free in the fetal circulation. In a 'non-responder' strain of mouse, as defined by the inability to detect anti-paternal alloantibody in the peripheral serum of multiparous allogeneically mated females, no alloantibody could be detected as soluble immune complexes, bound to the placenta or in the fetal circulation. A similar situation existed in females of a 'responder' strain during their first pregnancy and in some individuals during their second. However, in 'responder' strain females possessing alloantibody in their peripheral serum, alloantibody could be eluted from the semi-allogeneic placenta when peripheral titres exceeded 1:16, and was found in the fetal serum when they exceeded 1:128. When such females were subsequently mated syngeneically, alloantibody was detected in placental eluates only when peripheral titres exceeded 1:128-256 and in the fetal serum when they exceeded 1:16. The alloantibody eluted from placentae and that found in neonatal serum exhibited similar isotype distribution to that in the peripheral serum. These results are discussed with reference to the relative importance of the yolk sac and the immunoabsorbent semi-allogeneic placenta in the restricted transfer of pregnancy-induced anti-paternal alloantibody to the fetus.

Acute phase serum proteins in syngeneic and allogeneic mouse pregnancy

The levels of two murine acute phase proteins, serum amyloid P component (SAP) and haptoglobin, have been measured in the serum of C57BL/10 female mice during syngeneic and allogeneic pregnancy. Both syngeneic and allogeneic pregnancy resulted in alterations in the levels of these proteins as compared to those observed in virgin females. Syngeneic mating resulted in an increase in concentration of both proteins during the final 3 days of pregnancy. During allogeneic pregnancy, SAP levels, after a transient increase on day 4, rose from days 6-8 and, after remaining relatively stable, increased from day 12 to reach maximum levels on day 18 of pregnancy. Levels fell dramatically during the immediate post-partum period. In contrast, although levels of haptoglobin also increased from days 6-8, for the remainder of pregnancy these increased levels remained stable. The implications of these findings are discussed in relation to the mechanisms of regulation of acute phase reactants and the immunological relationship between the mother and fetus.

Immunoregulatory activity of supernatants from short-term cultures of mouse decidual tissue

Supernatants from short-term in-vitro cultures of decidual tissue, obtained from the uteri of pregnant mice from Days 4 to 13 post coitum (Day 1 = day of mating), were assessed for immunoregulatory activity by their addition to a mixed lymphocyte reaction (MLR), an in-vitro analogue of the afferent arm of the immune response. All culture supernatants tested possessed inhibitory activity in the MLR, although the extent of inhibition was affected by seeding density, length of culture, and the day of pregnancy from which decidual tissue was obtained. Inhibitory activity produced by decidual cultures increased from Day 4 to reach a maximum on Day 8, and then declined to Day 11. Two morphologically distinct cell types were present in all decidual cultures; flat dendritic cells, considered to represent decidual cells, and small round cells, but whether immunoregulatory factors are associated with both is uncertain. The results suggest that decidual tissue could fulfil a role in the local partial blockade of the afferent arm of the maternal immune response during pregnancy.

Partial characterization of immunosuppressive factors from short-term cultures of murine decidual tissue

Previous in vitro experiments provided evidence for the immunosuppressive properties of supernatants from short-term cultures of decidual tissue obtained from the uterus of the pregnant mouse. The inhibitory activity of supernatants, previously detected in a mixed lymphocyte reaction (MLR), has now been demonstrated in an in vitro thymocyte proliferation assay. Fractionation of these supernatants on Sephadex G-15 and Sephacryl S-300 revealed that inhibition of the thymocyte proliferation assay was associated only with a low molecular weight fraction (less than 1,500), whilst MLR inhibitory activity was associated with three different molecular weight fractions (less than 1,500, 60,000 and 1,000,000). These results are discussed in relation to the different biological factors previously isolated in decidua or deciduoma of rats and humans.

Ia antigen-bearing decidual cells and macrophages in cultures of mouse decidual tissue

The ontogeny of Ia antigen expression on cells within the decidua basalis of the placenta and on decidual cells differentiating in vitro was investigated in the mouse. The results indicate that Ia antigen expression is temporarily restricted and can be detected in short-term cultures of decidual tissue only during the final third of gestation. The Ia antigen positive cells, which are non-phagocytic, non-specific esterase negative and lack Fc receptors, appear to be true decidual cells on the basis of their fine structural characteristics. In contrast, morphologically identical dendritic decidual cells arising from differentiation in vitro of endometrial cells do not express Ia antigens. A population of small rounded cells was also present in cultures of both decidual tissue and in vitro decidualized endometrial cells. These rounded cells possess the macrophage-like properties of Fc receptors, non-specific esterase and phagocytic activity. The possible function of these cell populations within the decidual tissue is discussed.

Glycogen-induced intrauterine leucocytosis and its effect in mouse blastocyst implantation in vivo and in vitro

Intrauterine instillation of heat-deaggregated glycogen in virgin mice induced a marked but transient luminal infiltration of polymorphonuclear leukocytes (PMNL). Similar injections of glycogen 2 days post coitum resulted in termination of pregnancy in the majority of treated females. Embryos recovered on Day 4 of pregnancy from the glycogen-treated females, before the expected time of implantation, had developed to the cavitated blastocyst stage, and were capable of undergoing characteristic outgrowth when cultured in vitro. A small proportion, however, appeared abnormal and did not develop in vitro. Cavitated blastocysts obtained from control mated females did not undergo outgrowth in vitro in the presence of intact PMNL, homogenates of these cells or a low molecular weight (less than 1500) fraction of the homogenates and after culture appeared similar to the abnormal blastocysts recovered from glycogen-treated uteri. It is proposed that the anti-fertility effect of PMNL infiltrates is due to a low molecular weight component of these cells which acts in utero and is cytotoxic to preimplantation blastocysts before their hatching from the zona pellucida.

Humoral immune responses in murine pregnancy. II. Kinetics and nature of the response in females preimmunized against paternal alloantigens

The kinetics of anti-paternal alloantibody production in syngeneically and allogeneically mated mice previously immunized with allogenic spleen cells has been investigated. In allogeneically mated females, total and cytotoxic alloantibody levels increased during the final 3 days of pregnancy to reach maximal levels around 1 week after parturition. The properties of this alloantibody were indistinguishable from those of alloantibody induced by conventional immunization procedures. In syngeneically mated females no increase was observed. Total hysterectomy demonstrated that the immunogenicity of the conceptus required to produce a secondary humoral immune response was initiated in the majority of females between days 9 and 10 of pregnancy, and that the antigenic exposure by day 10 was sufficient to induce a maximal secondary response. These observations were consistent with the time of appearance of serologically demonstrable H-2 antigens on embryonic cells during pregnancy. These phenomena occurred in 'responder' and 'non-responder' female strains (referring to the ability of allogeneically mated females to produce anti-paternal alloantibody during normal pregnancy) demonstrating that they do not differ in their ability to produce a secondary immune response to alloantigens presented via the intrauterine route. The findings are discussed in relation to the nature of the immunogenic stimulus from the concepts in this system and during pregnancy.

Inhibitory activity of supernatants from murine decidual cell cultures on the mixed lymphocyte reaction

Supernatants from in vitro decidual cell cultures derived from uterine cells of C57BL mice were assessed for immunoregulatory activity by addition at the initiation of a mixed lymphocyte reaction (MLR) between C57BL responder and Balb/c stimulator splenocytes. MLR inhibitory factors were present during two phases of the culture; firstly during decidual cells differentiation and secondly during involution of the culture. These factors were produced whether the cultures were derived from syngeneically or allogeneically mated mice. Addition of supernatants 24 h after the initiation of the MLR also produced an inhibitory effect. Throughout the culture period supernatants also inhibited the control MLR containing C57BL responder and stimulator splenocytes. Peaks of inhibitory material were associated with both high (greater than 1 500) and low (less than 1 500) molecular weight fractions as assessed by Sephadex G15 fractionation. No inhibitory factors were identified in supernatants from similar cultures of embryonic fibroblasts. The results are discussed with respect to the mode of action of these factors and their possible role in the maintenance of the foetal allograft.

Humoral immune responses in murine pregnancy. I. Anti-paternal alloantibody levels in maternal serum

The kinetics and properties of anti-paternal alloantibody produced by female C57BL(H-2b) mice in response to mating with CBA(H-2k) males have been investigated using an immunobead adsorption assay. No alloantibody was ever detected in the first pregnancy or post-partum period. 72% of females exhibited a humoral response in their second pregnancy, detectable from day 16 or 17 post-coitum, and almost all females responded in their third pregnancy. Column chromatographic and immunoelectrophoretic analysis showed that the alloantibody was IgG. Although passive transfer experiments suggested similar stability characteristics to those of cytotoxic antibody induced by experimental hyperimmunization, the pregnancy-induced alloantibody did not exhibit complement-dependent cytotoxicity. The findings are discussed in relation to the nature of the immunogenic stimulus from the conceptus and the regulation and possible function of the humoral immune response in allogeneic pregnancy.

Differentiation of decidual cells in mouse endometrial cell cultures

Mouse uterine cells were obtained by trypsinization of uteri at timed intervals after the induction of a decidual reaction by intraluminal instillation of arachis oil on Day 4 of normal pregnancy. Cells were also obtained from ovariectomized mouse uteri, some of which had received a progesterone-oestradiol sequence to sensitize the uterus to a decidual stimulus. The differentiation of decidual cells was followed in cultures of these cells. The morphology of the cells obtained after 6 days in culture was dependent upon the seeding density employed. At low seeding density (plating densities of 75-100 cells/mm2) no net increase in cell number was observed, but large mononucleated stellate cells were present, with cytoplasmic and nuclear areas increased by 4-fold. At higher seeding densities (plating densities of up to 709 cells/mm2), a prolongation of cell survival and the appearance of substantial numbers of binucleated cells were observed. However, both cell types were characterized by the accumulation of filamentous material in the cytoplasm. Even at optimal seeding density the life-span of the decidualized cells could not be prolonged beyond 9 days. Uterine cells from hormone-treated ovariectomized animals underwent similar transformations but those from untreated ovariectomized mice gave only isolated islets of epithelial cells and scattered fibroblast-like cells in culture. These observations suggest that discrepancies in previous reports of in-vitro deciudualization of rat uterine cells result from differences in the seeding densities employed.

Major anti-paternal alloantibody induced by murine pregnancy is non-complement-fixing IgG1

Maternal humoral responses against antigens of the genetically alien embryo have been reported in several mammalian species, including man, although little is known of the biological relevance of this phenomenon. In the mouse, only females of certain inbred strains mated repeatedly with an allogeneic male produce antibody directed against paternally inherited fetal histocompatibility antigens, as assessed by haemagglutination techniques. It has been suggested that this characteristic of the female is associated with the H-2 haplotype, although some reports indicate that it also extends to other H-2 types. Potentially deleterious complement-dependent cytotoxicity, albeit at low levels, has been claimed to be associated with this alloantibody, but we have been unable to detect any such activity in a large number of maternal sera. Four IgG isotypes (IgG1, IgG2a, IgG2b and IgG3) have been identified and shown to occur in the serum of normal animals. Despite their similar physicochemical properties, which complicate purification procedures, the availability of immunoglobulin-secreting plasmacytomas has made possible the preparation of isotype-specific antisera. Using these antisera in modified haemadsorption assay, we have now demonstrated that the major alloantibody response induced by murine pregnancy involves the non-complement-fixing IgG1 subclass. This is a noncytotoxic antibody with potentially protective (enhancing) properties.

Effects of oestradiol and progesterone on the concentration of alpha 2-macroglobulin in the sera of injured male and female rats

The effects of ovarian hormones on the synthesis of alpha 2-macroglobulin in response to injury were investigated. After injection of turpentine to provoke synthesis of alpha 2-macroglobulin, the mean concentrations of this protein in serum were lower in intact female than in male rats. Sera from injured ovariectomized rats contained levels of alpha 2-macroglobulin similar to those of injured male animals. Administration to ovariectomized animals of oestradiol or oestradiol plus progesterone substantially reduced the levels of alpha 2-macroglobulin produced in response to injury. Administration of progesterone only resulted in a small increase in the response of ovariectomized animals to injury. Oestradiol and progesterone had no effect on the response of male rats to injury. These findings suggest that only in the female rat can these steroid hormones, especially oestradiol, regulate the synthesis of alpha 2-macroglobulin in response to tissue injury.

Immunopharmacologic properties of 1,6-bis[2-(diethylamino)ethoxy]xanthen-9-one dihydrochloride (Wy-15297)

When tested in a series of immunopharmacologic assays, the interferon inducer, WY-15297, was shown to lack activity in early vascular and humoral phases of the inflammatory response, while it was quite effective against the immunologic phase. The profile of activity of Wy-15927 was, however, unlike those previously described for reference antiinflammatory and immunosuppressive drugs and this may represent one of a new class of immunopharmacologic agents capable of selectively modulating the lymphoreticular system.

Synthesis of 'decidualization-associated protein' in tissues of the rat uterus and placenta during pregnancy

The synthesis of a soluble protein (referred to as 'decidualization-associated protein', DAP), has been examined in uterine and placental tissues of rats during pregnancy by means of polyacrylamide gel electrophoretic analysis of [3H]leucine-labelled soluble proteins. No synthesis of the protein was detected in non-implantation regions of the uterus. In implantation site tissue, no synthesis was detected on Days 6 or 7 of pregnancy. Only slight synthesis was present in the endometrium on Day 8, but synthesis rose rapidly from Days 9 to 12 in both the endometrium and myometrium although differences in the rates of increase were observed. Synthesis fell from Day 12 to 14 in both tissues. Synthesis by the myometrium was entirely localized in the mesometrial region, which contains the metrial gland. After Day 12, when the endometrium is represented by the chorioallantoic placenta, synthesis was examined in the labyrinthine and the decidua basalis/basal zone placenta tissues. No synthesis of 'DAP' was detected in the labyrinthine placenta from Day 16 of pregnancy. Synthesis observed in the decidua basalis/basal zone placenta fell dramatically from Day 14 to 20. The pattern of synthesis of 'DAP' during pregnancy suggests a role in the establishment of the chorioallantoic placenta and metrial gland in the rat.

Bacterial catabolism of threonine. Threonine degradation initiated by L-threonine acetaldehyde-lyase (aldolase) in species of Pseudomonas

1. The route of l-threonine degradation was studied in four strains of the genus Pseudomonas able to grow on the amino acid and selected because of their high l-threonine aldolase activity. Growth and manometric results were consistent with the cleavage of l-threonine to acetaldehyde+glycine and their metabolism via acetate and serine respectively. 2. l-Threonine aldolases in these bacteria exhibited pH optima in the range 8.0-8.7 and K(m) values for the substrate of 5-10mm. Extracts exhibited comparable allo-l-threonine aldolase activities, K(m) values for this substrate being 14.5-38.5mm depending on the bacterium. Both activities were essentially constitutive. Similar activity ratios in extracts, independent of growth conditions, suggested a single enzyme. The isolate Pseudomonas D2 (N.C.I.B. 11097) represents the best source of the enzyme known. 3. Extracts of all the l-threonine-grown pseudomonads also possessed a CoA-independent aldehyde dehydrogenase, the synthesis of which was induced, and a reversible alcohol dehydrogenase. The high acetaldehyde reductase activity of most extracts possibly resulted in the underestimation of acetaldehyde dehydrogenase. 4. l-Serine dehydratase formation was induced by growth on l-threonine or acetate+glycine. Constitutively synthesized l-serine hydroxymethyltransferase was detected in extracts of Pseudomonas strains D2 and F10. The enzyme could not be detected in strains A1 and N3, probably because of a highly active ;formaldehyde-utilizing' system. 5. Ion-exchange and molecular exclusion chromatography supported other evidence that l-threonine aldolase and allo-l-threonine aldolase activities were catalysed by the same enzyme but that l-serine hydroxymethyltransferase was distinct and different. These results contrast with the specificities of some analogous enzymes of mammalian origin.