Effects of placental extracts on the immune response to histocompatibility antigens: class deviation of alloantibody response and allograft enhancement

Trace metals and metalloenzymes in placenta after oral administration of lead acetate

The present study was carried out to find the effects of Pb acetate (10-50 mg/kg body wt) after oral administration on: 1. The distribution of elements, such as Fe, Cu, Zn, and Mn; 2. The activity of 6-amino levulenic acid dehydratase (delta-ALAD) and alkaline phosphatase (PAP); and 3. On the level of reduced glutathione (GSH) in murine placenta. Pb toxicity expressed on a dry-wt basis was reflected in terms of deficiency of delta-ALAD and PAP and enhanced content of GSH. Analysis of trace elements following Pb exposure showed low levels of Mn and Cu. Although Fe composition of placenta remained within normal range with increasing load of endogeneous Pb, Zn decline was not consistent after oral feeding of Pb acetate. Deficiency of PAP after Pb exposure did not correlate with the endogeneous levels of Pb or Zn therein, but correlated with endogeneous levels of Mn. Placental deficiencies of Cu and Mn have been related to the disturbed placental functions by Pb accumulation.

Immune responses of chemically modified homologous LDH-C4 and their effect on fertility regulation in mice

PROBLEM

Lactate dehydrogenase-C4 (LDH-C4) is an iso-, allo- and auto-antigen of mammalian sperm. In spite of being cell specific, LDH-C4 does not induce infertility in females of homologous species after immunization. The present study examines the application of homologous LDH-C4 after chemical modifications in the immunological infertility of female mice.

METHODS

LDH-C4 from testes of LACA mice was chemically modified by interacting it with gossypol (gossy-LDH-C4) and glucosylation with lactose (Glu-LDH-C4) in vitro and evaluated for immune responses and induced immunological infertility in allogeneic Balb/c mice after inoculation through intrarectal route using A1(OH)3 as adjuvant.

RESULTS

Native LDH-C4, which elicited high antibody response after immunization with a primary (50 microgram) and three secondary doses (30 micrograms each) at an interval of 15 days each, did not reduce fertility significantly in mice. In contrast, study provides evidence that chemically modified LDH-C4 induces high infertility, since 85-100% of mice failed to conceive in two independent sets of experiments. Mice inoculated with modified LDH-C4 were associated with 2-3 fold anti-LDH-C4 antibody titre compared to antibody response elicited by native LDH-C4. Splenocytes from immunized non-pregnant mice were evaluated for polyclonal activation using Con A as mitogen. It was found that splenocytes primed with native LDH-C4 were significantly more stimulated than the non-immune control cultures. However cells primed with gossy-LDH-C4 were non-reactive to Con A and cells primed with glu-LDH-C4 were suppressed for ConA proliferation.

CONCLUSIONS

It is concluded that LDH-C4-gossypol adduct offers a potential application in the induction of infertility of homologous species in marked contrast to native LDH-C4. Application of A1(OH)3 as adjuvant in the induction of immune response through intra-rectal route has been suggested.

Effects of the whole extract and the chromatographic fractions of the pig placenta on lymphocyte proliferation and humoral immune response

The immunoregulatory properties of pig fetal placenta extracts (PE) from 1 st, 2nd and 3rd month of pregnancy and five fractions (F1 to F5), isolated on Sephadex G-200 and additionally characterized by fast performance liquid chromatography, FPLC (Superose 12 HR) were studied in order to clarify the local immune regulation in diffuse epitheliochorial placentation. The obtained substances were added at 6.25 to 100 microg in cultures of Concanavalin A-stimulated mouse splenocytes and Phytohemagglutinin-stimulated pig and human PBL to monitor their influence on [(3)H]Thimidine uptake in proliferating lymphocytes. Their effects on the number of plaque-forming cells in spleen cell suspensions from mice treated ip simultaneously with sheep red blood cells and with 100 microg protein of PE, respectively, of each fraction were also investigated: PE and F1 had no effect while F4 and F5 suppressed the mitogen-induced lymphocyte proliferation in all studied species. F2 and F3 stimulated mouse and pig lymphocyte proliferation. The effects were dose-dependent and the suppression was not due to cytotoxic effects. The FPLC data allowed the suggestion that 110 kD protein(s) were involved in stimulation and 7 kD substance(s) - in suppression of cell proliferation. The PE from the 3 studied periods as well as the 5 fractions increased significantly the primary humoral immune response against T-dependent antigen. The results revealed that trophoblast of epitheliochorial placenta produces simultaneously immuno-stimulatory and -suppressive factors acting across the species barrier. Their presence at the feto-maternal interface may contribute to the regulation of local immune reactions and survival of the allogenic fetuses despite the morphological specificities of this type of placentation.

Modulation of allo-immune responses in vivo and in vitro by sperm specific lactate dehydrogenase-C4

The role of sperm specific lactate dehydrogenase-C4 (LDH-C4) in allo-immune responses using mixed lymphocyte cultures (MLC) and cytotoxic T cell (CTL) generation in vitro and local graft versus host (LGVH) reaction and allograft enhancement in vivo has been ascertained. LDH was purified from testes (LDH-C4) and kidney (LDH-B4) of C57Bl/Ks mice. MLC and CTL were performed using C57Bl/Ks-anti A/J lymphocytes in presence of 10(-3)-1 micrograms LDH-B4 or LDH-C4 per culture. The MLC and CTL responses showed biphasic action depending on the dose of LDH-C4. Early MLC culture gave significantly low stimulation index at 10(-2)-10(-1) micrograms LDH-C4 as compared to non-treated control cultures. However, the MLC response in presence of LDH-C4 was not different from the LDH-B4 treated one which showed a similar biphasic trend. On the other hand, 51Cr release from YAC-222 target cells was practically abolished by LDH-C4 at 10(-3)-1(-1) micrograms, and this was strikingly different from LDH-B4 or non-treated cultures. LGVH reactivity as performed by using C57Bl/Ks lymphocytes along with LDH-C4 in (C57Bl/Ks x A/J) F1 hybrids indicated a suppression of stimulation index in primary and secondary (i.e. preimmunized in presence of LDH-C4 or LDH-B4) LGVH. Allograft enhancement of Sa I (A/J) in C57Bl/Ks mice in presence of LDH-C4, was delayed slightly but significantly during primary or secondary transplantation reaction.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunoactive products of human placenta. IV. Immunoregulatory factors obtained from cultures of human placenta inhibit in vivo local and systemic allogeneic and graft versus-host reactions in mice

We have shown in previous reports that human placental supernatants (HPS) display a variety of immunoregulatory properties in vitro. Here we report that these supernatants are able to suppress the ability of murine splenocytes to evoke an allogeneic reaction in the popliteal lymph node (PLN) assay, as well as their capacity to induce both local (popliteal lymph node swelling) as well as systemic chronic or lethal graft-versus-host reactions. Those results are discussed in the light of the potential use of HPS in the control of transplantation immune reactions as well as in the regulation of xenogeneic pregnancies, as the murine system that was used proved that the material exerted an effect across a species barrier.

In vitro immunomodulatory effects of placental substances on preparatory MLR and resulting modifications of lymphocyte reactivities

The immunomodulatory effects of murine placental extracts (PE) were studied in vitro using mixed lymphocyte culture (MLC) and resulting cell-mediated lympholysis (CML). The results showed that preparative cultures in the presence of PE syngeneic to the responding cells led to a low secondary MLR response with a concomitant generation of suppressor cells. At the efferent phase, cells from the same preparative culture showed a weaker cytotoxic activity than controls cultured in the absence of extract. Furthermore, the induction of regulatory cells able to inhibit CTL in vitro activity was also observed. The active substances can be found in the 30% ammonium sulphate precipitate as well as in some gel filtration fractions showing several main bands from 115 to 43 kDa in SDS-PAGE.

Effect of a soluble factor secreted from cultured human trophoblast cells on in vitro lymphocyte reactions

The immunoregulatory role of trophoblast cells in cell-mediated immunity was investigated. Trophoblast cells were obtained from 8-10-week human placentae by treatment with collagenase followed by differential centrifugation. The cells were cultured for 48 hr, and the culture supernatant was examined for immunosuppressive activity in vitro. The supernatant when added to cultures of peripheral blood lymphocytes from healthy donors suppressed both their reactivity to different lectins (PHA and PWM) and their activity in one-way mixed lymphocyte reaction. The degree of suppression was dose-dependent. Furthermore, the supernatant was able to reduce the natural killer cell activity against K562 target cells. On the other hand, the supernatant had no inhibitory effect on the effector phase of lymphocyte-mediated cytotoxicity activity against tumor cell lines RPMI 8866 and Daudi. In all cases, the suppression observed was not due to lymphocytotoxicity or tumor cell mortality. The results indicate that trophoblast cells release a soluble suppressive factor that is a potent inhibitor of cell-mediated immunity.

Antibody isotype produced by pregnant mice immunised with fetal allogeneic lymphocytes is mainly IgG1

Virgin and Pregnant BALB/c mice were immunized three times with (BALB/c X CBA)F1 fetal or adult lymphocytes. An enzyme linked immunosorbent assay (ELISA) was developed for analysing the isotypes and specificities of the alloantibody produced. Pregnant mice immunized with fetal lymphocytes showed an immunodeviation towards IgG1 production compared with other groups.

Placental immunoregulatory factors

Local immune suppression appears to be a key feature in the success of the fetal allograft. Various placental factors have been described endowed with immunoregulatory activity. Much of the available evidence concerning the biological function and biochemical characteristics of these molecules is reviewed here, as well as the controversial issues surrounding them. In the final section, some outstanding questions relating to these immunoregulators are considered.

Maternal alloimmune reactions towards the murine conceptus and graft-versus-host reaction (GVHR). II. Inhibition of priming by placental extracts

Gestation can induce a priming for a GVHR towards paternal strain antigens, although this priming is significantly lower than the one induced by experimental immunization. A role has been sought for placental substances in decreasing this priming through immunomodulation. BALB/c (H-2d) spleen cells do not usually induce a systemic, lethal GVHR in DBA/2 (H-2d) newborn mice except when the donors are preimmunized with DBA/2 cells. Placental extracts (as well as RPMI medium or liver extracts used as controls) were added to DBA/2 cells injected into BALB/c mice used as cell donors for GVH induction. The latter's spleen cells, harvested on day 6 after immunization, were used for systemic and local GVHR. In the systemic assay (lethal effect on DBA/2 newborn mice injected i.v. with BALB/c spleen cells) a significant protection was observed. In the local assay (popliteal lymph node assay in F1 hybrids injected with BALB/c spleen cells into the foot-pad) a highly significant inhibition of priming was detected in recipients injected with spleen cells from placental extract-treated donors. The stimulation index was even lower than that obtained with unprimed BALB/c spleen cells. The same type of local GVHR in (CBA/Ca X A/J) F1 hybrids injected with CBA cells led to similar results. In both situations (systemic and local GVHR) the observed inhibition was found to be specific to the priming cell strain. These results support the working hypothesis that placental substances are able to modify the systemic response of an organism towards both H-2 and non-H-2 alloantigens.