Asymmetric antibodies: a protective arm in pregnancy.

In normal conditions, a simple change in the pattern of cytokines towards a Th2 response is associated with the production of aggressive antibodies. This fact could not completely explain phenomena such as the fetal survival or the chronicity of certain infections. However, it has been demonstrated that Th2 cytokines increase the proportion of asymmetric antibodies, which are unable to activate effector immune mechanisms (complement fixation, clearance of antigens and phagocytosis). Investigations of asymmetrically glycosylated antibodies demonstrated that these IgG molecules have an extracarbohydrate in one of the Fab regions. This glycosylation affects their antigen interaction turning them into a functionally univalent and blocking antibodies. It has been established that their synthesis is increased under different physiopathological situations involving Th2 responses: chronic infections by extracellular microorganisms, pregnancy and allergic processes. In this review we summarize the experiments performed by our research group over the last years as well as the advances made concerning the role and mechanism of asymmetric antibodies.

Interleukin-6 and dexamethasone modulate in vitro asymmetric antibody synthesis and UDP-Glc glycoprotein glycosyltransferase activity.

The increased production of asymmetric IgG protective antibodies is one of the mechanisms proposed to explain a successful semiallogeneic pregnancy. We have previously demonstrated that IL-6 was able to enhance the synthesis of these antibodies by a murine hybridoma, while the glucocorticoid dexamethasone (DEXA) diminished it. In order to investigate the mechanism of asymmetric antibody synthesis, we investigate the role of UDP-Glc glycoprotein glucosyltransferase (GT), an endoplasmic reticulum enzyme involved in the quality control and folding of glycoproteins. Either recombinant murine rmIL-6 (0-10-40-160-320-640 ng/ml) or DEXA (0.15 microM) were added to a mouse hybridoma culture and incubated for 24 and 72 h in the first case, and for 4h in the presence of DEXA. Anti-DNP asymmetric antibodies were determined in the culture supernatants by ELISA. After harvesting, hybridoma cells were sonicated and GT activity was analysed in isolated microsomal fractions by measuring UDP((14)C)-Glc incorporation into urea-denatured thyroglobulin (urea-Tg). In the present paper, we showed that IL-6, mainly at 40 ng/ml and t=24h, was able to upregulate both in vitro GT activity (+74%) and asymmetric molecule synthesis (+227%). Lower increases were obtained employing 10 and 160 ng/ml. On the other hand, DEXA, at 0.15 microM and t=4h, showed a mild inhibition of enzyme activity (-10%) and a diminished proportion of asymmetric IgG (-49%). A direct relationship between GT activity and proportion of the asymmetric antibody synthesised was found in our hybridoma cells employing IL-6 and DEXA in different conditions, as was indicated by a correlation analysis. These results suggest that GT might be involved in the synthesis of asymmetric antibodies.

Analysis of macrophage presence in murine placenta: influence of age and parity status.

PROBLEM: Beneficial effects of multiparity status have been previously reported by different authors. However, this fact has not been fully explained. Taking into consideration the influence of the parity status on the in vitro asymmetric/protective antibodies and the fact that interleukin-6 (IL-6) is involved in the production and immune-regulatory functions of placental macrophages, the aim of this work was to compare the placental IL-6 production and tissue macrophage presence in mice with different age and parity status. METHOD OF STUDY: Three groups of mice (CBA/J x CBA/J) were analyzed: primiparous young (PY: 3.0 +/- 0.5 months old), primiparous old (PO: 8.5 +/- 0.5 months old), and multiparous old (MO: 8.5 +/- 0.5 months old, with three to four previous pregnancies). Macrophage and IL-6 were identified in placental tissue by immunohistochemistry employing anti-F4/80 or anti-IL-6 antibodies. IL-6 secretion was analyzed in the placental culture supernatants by enzyme-linked immunosorbent assay. RESULTS: The results obtained indicate that, despite the level of macrophages observed in the PO placentae was higher than in PY ones, their expression in MO placentae was very much increased, appearing like a thick layer between decidua and trophoblast. However, no significant difference was found among the groups in the tissue expression of IL-6 and in IL-6 secreted in vitro. CONCLUSIONS: Our data indicate that parity status influences the number of local macrophages and might provide evidence that could explain the known beneficial effect of multipaternity. We suggest that the number of previous pregnancies favor the production of a 'protective' population of macrophages.

Regulation of interleukin-6 fetoplacental levels could be involved in the protective effect of low-molecular weight heparin treatment on murine spontaneous abortion.

PROBLEM: CBA/J x DBA/2 abortion rate could be the consequence of a deficient local production of T helper (Th2) cytokines, which cause fetal wastage via fgl2 prothrombinase. Heparin reduces significantly the abortion rate in mice and recurrent spontaneous abortion (RSA) patients. We proposed to determine the effect of enoxaparin on the levels of local interleukin (IL)-6 during murine pregnancy. METHOD OF STUDY: Recombinant human IL-6 (rhIL-6) or enoxaparin were inoculated in CBA/J x DBA/2 pregnant mice on days 6.5-12.5. IL-6 levels in sera as well as in culture supernatants of day 9.5 fetoplacental units of CBA/J x BALB/c control mice or CBA/J x DBA/2 abortion combination were determined by enzyme-linked immunosorbent assay (ELISA) test. RESULTS: CBA/J x DBA/2 fetoplacental units secreted significantly lower levels of IL-6 with regard to CBA/J x BALB/c normal units. rhIL-6h and enoxaparin treatments decreased the resorption rate and regulated IL-6 fetoplacental levels. CONCLUSION: This study suggests that regulation of IL-6 fetoplacental levels could be involved in heparin-mediated anticoagulation protection against abortion.

Characterization of human infection by Leishmania spp. in the Northwest of Argentina: immune response, double infection with Trypanosoma cruzi and species of Leishmania involved.

The aims of this study were to characterize human American tegumentary leishmaniasis, which includes cutaneous, mucocutaneous and mucosal leishmaniasis, in Northwest Argentina, to determine the prevalence of double infection with Trypanosoma cruzi and to identify the species of Leishmania in this area. Most of the 330 leishmaniasis patients presented cutaneous ulcers (96.1%), 2.4% mucocutaneous and 1.5% the mucosal form ('espundia'). The aetiological agents, determined by isoenzyme electrophoresis, were identified as Leishmania (Viannia) braziliensis in 16 out of 20 isolates and in the remaining 4 as Leishmania (Leishimania) amazonensis, the first ever-documented in Argentina. Sera analysed by ELISA and IFA using complex antigen from both T. cruzi and L. braziliensis showed a very high percentage of positives (66.3-78.2%). When antigens for specific diagnosis of Chagas' disease were used, 40.9% of the leishmaniasis patients were also found to be infected by T. cruzi. These results indicate that the strong immune response against T. cruzi gave no protection to Leishmania, in spite of the serological cross-reaction between these parasites. In addition, we showed that more than 40% of the patients would be misdiagnosed as chagasic if complex antigens, as epimastigotes or soluble fraction from epimastigotes, were used in IFA or ELISA. This is of paramount importance not only because patients' treatment would be associated to misdiagnosis but the fact that in many countries in Central and South America, a positive test for Chagas' disease means a rejection for those seeking employment.

Anticuerpos asimétricos: el arma de protección antigénica en la respuesta inmune regulada por Th2 / Asymmetric antibodies: the antigen protective arm in a Th2-regulated immune response

Está bien aceptado que, durante el embarazo, las infecciones por micro organismos extracelulares y los procesos alérgicos -aparte de otras condiciones-, los adultos inmunocompetentes montan respuestas inmunitarias Th2 que implican un aumento de la producción de anticuerpos. Considerando que los anticuerpos son capaces de activar mecanismos inmunitarios efectores tales como la fijación de complemento, el aclaramiento de antígenos y la fagocitosis, un simple desvío de las citocinas implicadas en ese cambio podrían no explicar completamente fenómenos tales como la supervivencia fetal y la cronicidad de ciertas infecciones. Hace unos veinte años que comenzamos nuestras investigaciones sobre anticuerpos asimétricamente glicosilados. Así probamos que la presencia de un carbohidrato extra en una de las regiones Fab de la molécula de IgG, afecta a la interacción con el antígeno y determina su univalencia característica y sus propiedades bloqueantes. En el presente estudio, revisaremos las principales propiedades de este tipo de anticuerpos y reportaremos nuestros hallazgos en distintos procesos fisiopatológicos. (AU)

Interleukin regulation of asymmetric antibody synthesized by isolated placental B cells.

PROBLEM: Protecting antibodies against trophoblast surface molecules were previously described. Here we analysed the synthesis of asymmetric IgG by placental B-lymphocytes. METHOD OF STUDY: B cells were isolated from human term placenta and cord blood, stimulated with anti-CD40 IgG and cocultured with transfected Fcgamma R-expressing mice Ltk-fibroblast. Interleukin-4, IL-6, IL-10, IL-11 and IL-13 were added to cultures for 14 days. Asymmetric IgG were assessed in culture supernatants by concanavalin A (Con A) fixation and enzyme-linked immunosorbent assay. RESULTS: When IL-6 was added to the cultures, the percentages of asymmetric IgG synthesized by placental B cells were: IL-6: 29 +/- 10; IL-6 + IL-10: 24 +/- 7; IL-4 + IL-10 + IL-6: 38 +/- 9. The last combination induced the highest increase in the asymmetric IgG synthesis as compared with control (19 +/- 10%, P < 0.05). Additionally, placental B cells synthesized more asymmetric IgG than umbilical cord blood B-lymphocytes (P = 0.0015). CONCLUSIONS: Isolated placental B-lymphocytes synthesized asymmetric IgG in response to Th2 interleukins, more notably IL-6 in combination with IL-4 and IL-10. The in vitro increase of protective asymmetric IgG synthesis in response to Th2-cytokines support the hypothesis that a local Th2-switch is beneficial for pregnancy outcome.

Enhancement of in vitro hsp72 expression by placental IL-6.

PROBLEM: To give an approach in order to elucidate the mechanism by which placental IL-6 induce modifications in the glycosylation status of immunoglobulins, in the present work, we investigate a putative relationship between a stimulus by placental IL-6 and expression of cytoplasmic "hsp70 family proteins" in an in vitro model. METHODS OF STUDY: Supernatants of cultures of placentae obtained from primiparous and multiparous AKR/J x AKR/J and AKR/J x BALB/c mouse crossbreedings were added to mouse IgGI hybridoma cultures which produced symmetric and asymmetric anti-dinitrophenol (anti-DNP) antibodies. Analyses of the expression of inducible hsp72/constitutive hsp73 in cellular lysates obtained from hybridomas cultured, in the presence of rmIL-6 or crude murine placental culture supernatants, followed by neutralization assays with anti IL-6, were performed. In addition, the level of IL-6 present in the employed placental culture supernatants was determined and compared with the placental hsp70-inducing effect. RESULTS: These experiments showed that mouse placentae were able to release IL-6 in vitro. In addition, mouse placental supernatants (PS) containing over 1,000 pg/mL of IL-6 enhanced the expression of the inducible isoform hsp72 in the employed hybridomas. This effect was abolished when the hsp70-inducing PS were previously incubated with anti-mIL6 antibody. CONCLUSIONS: These observations indicate that mouse placentae produce different titers of IL-6 and suggest that IL-6 appears to be the unique mouse placental factor able to induce in vitro hsp72 synthesis. A relationship with the increased synthesis of anti-paternal antigen asymmetric antibodies, previously observed during pregnancy, is discussed.

During pregnancy, in the context of a Th2-type cytokine profile, serum IL-6 levels might condition the quality of the synthesized antibodies.

PROBLEM: In recent years, the central role of cytokines in the immune response has been widely studied. It is considered that a T helper (Th)1-type cytokine profile is associated with the rejection phenomenon, whereas a Th2-type cytokine profile is associated with immunological tolerance. In pregnancy, the enhanced Th2/Th1 ratio seems to be necessary to fetal protection. Taking into account that a Th2-type response means antibody production by B cells, and that these antibodies could induce degradation of the paternal antigens, we investigated the quality of the antibodies produced during pregnancy and their regulation. METHOD OF STUDY: Review of previous data. RESULTS: The regulation of protective antibodies by IL-6 in a dose-dependent fashion is proposed as a hypothesis. CONCLUSION: Cytokines play a central role in the success (or failure) of pregnancy. However, the quality of the synthesized antibodies is also a regulatory key. The preferential synthesis of asymmetric immunoglobulin G antibodies during pregnancy could be one of the several pathways that lead to a successful pregnancy

Asymmetric antibodies and pregnancy.

PROBLEM: Asymmetric IgG antibodies (AAb) possess a mannose-rich oligosaccharide residue bound to one of the Fab regions, making them unable to activate immunoeffector mechanisms. The proportion of asymmetric antibodies is increased after prolonged immunization with particulate antigens like cellular spleen cells. During pregnancy, AAb were found in serum and bound to placenta with specific activity to paternal antigens. No previous reports about the status of AAb in recurrent spontaneous abortion (RSA) patients have been published to date. Therefore, the aim of the present study was to analyze the percentage of asymmetric IgG molecules in serum samples of (a) healthy pregnant and non-pregnant women, (b) pregnant women with a history of RSA, and (c) non-pregnant RSA patients receiving paternal lymphocyte immunotherapy (LIT) or intravenous gammaglobulin therapy (IVIgs). METHOD OF STUDY: A previously-described differential ELISA technique was used to determine the percentage of IgG that was of the asymmetric type. RESULTS: During normal pregnancy, there was an increase in the percentage of high ConA affinity IgG serum molecules with a major increase at the second trimester. Pregnant RSA patients at the second trimester had lower values. When evaluating non-pregnant RSA patients who received LIT, it was observed that the immunized patients expressed a higher percentage of asymmetric IgG antibodies. The pregnant patients who received IVIgs had a percentage of AAbs comparable to normal pregnant patients. Additionally, the presence of IgG asymmetric molecules was confirmed in commercial gammaglobulin preparations. CONCLUSION: Results suggest a protective role of AAb during pregnancy.

The placental regulatory factor involved in the asymmetric IgG antibody synthesis responds to IL-6 features.

Pregnancy success is attributed to the joint action of several factors such as regulatory placental molecules and components of the mother's immune system, among others. Asymmetrical glycosilated and functionally univalent IgG antibodies are suggested to influence the immune balance between the mother and foetus, playing a meaningful role on the foetal survival in the maternal uterus. Placental secretory factors might be responsible for the increase of these molecules during gestation. Since placental factors appeared to be the inducers of these high Concanavaline A-affinity (Con-A) IgG molecules our work was focused on the identification of such factors. The chromatographic separation of placental culture supernatants (PCS) allowed the detection of fractions capable of increasing the high Con-A affinity monoclonal antibody (Mab) ratio synthesised by a hybridoma. The presence of multimeric placental forms of interleukin 6 (IL-6) could be identified in these fractions. Considering that IL-6 modulates protein glycosylation we decided to investigate its effect on the monoclonal IgG glycosylation. When placental IL-6 containing fractions or rIL-6h were added to hybridoma cultures, the proportion of asymmetric IgG antibodies increased substantially.

Hallazgos inmunohistoquímicos en material histopatológico de abortos recurrentes espontáneos / Immunohistochemical findings in histopathological material of spontaneous recurrent abortions

En 1994 en un estudio realizado por nuestro grupo en colabaración con la Dra. Fuksman sobre 1.200 placentas correspondientes a embarazos de alto riesgo, se halló la presencia de villitis en el 5.6 por ciento de las mismas. La histopatología detectada en ese momento fue deciduitis linfocitaria y aumento de fibrina perirvellositaria asociada con hipoirrigación e infarto placentario. Hallamos que en el 55 por ciento de las placentas con villitis los recién nacidos presentaban RCIU con respecto al 10 por ciento de los controles, con un PA de 32 por ciento en las villitis y el 83 por ciento en los controles (3). En ese material se estudiaron 68 placentas con villitis y 68 placentas sin villitis como grupo control. En 1996 demostramos en ese mismo material mediante la técnica de anticuerpos monoclonales, sobre cortes de placenta estudiando las subpoblaciones linfocitarias de las villitis, que el 50 por ciento eran CD4 (linfocitos helper), 18 por ciento CD8 (linfocitos supresoreslcitotóxicos) y 10 por ciento Leu19 (Natural Killer) pero lo significativo y anormal es que hallamos que el 65 por ciento de los linfocitos expresaban antígenos de histocompatibilidad clase II DR (40). En 1998 Jacques y Col publicaron datos similares. En 1999 comunicamos que en el informe histopatológico de material de legrado de pacientes abortadoras de causa inmunológica la descripción de villitis en un 20 por ciento de los casos. Estudios realizados en colabaración con la Dra. Zenclussen con ese material nos permitió publicar recientemente la presencia de altos niveles de Interleuquina 6(IL-6) y receptor de IL-6 en suero. El objetivo de este estudio es investigar en placentas de pacientes abortadoras recurrentes la expresión de IL-6 y sus receptores gp80 y gp130 en trece muestras de material de raspado de abortos del primer trimestre mediante la técnica de inmunofluorescencia. Como control se utilizaron cortes de placentas de embarazos normales a término. Nuestros hallazgos muestran la presencia de depósitos de IL-6 y de receptores de IL-6 con un patrón granular para las tres moléculas especificamente en el sinciciotrofoblasto mientras que fue negativo para tres en el citotrofoblasto. En los cortes de placentas normales no se hallaron en ningún caso dichos depósitos. Concluímos de todos los hallazgos antes sintetizados...

Hallazgos inmunohistoquímicos en material histopatológico de abortos recurrentes espontáneos / Immunohistochemical findings in histopathological material of spontaneous recurrent abortions

En 1994 en un estudio realizado por nuestro grupo en colabaración con la Dra. Fuksman sobre 1.200 placentas correspondientes a embarazos de alto riesgo, se halló la presencia de villitis en el 5.6 por ciento de las mismas. La histopatología detectada en ese momento fue deciduitis linfocitaria y aumento de fibrina perirvellositaria asociada con hipoirrigación e infarto placentario. Hallamos que en el 55 por ciento de las placentas con villitis los recién nacidos presentaban RCIU con respecto al 10 por ciento de los controles, con un PA de 32 por ciento en las villitis y el 83 por ciento en los controles (3). En ese material se estudiaron 68 placentas con villitis y 68 placentas sin villitis como grupo control. En 1996 demostramos en ese mismo material mediante la técnica de anticuerpos monoclonales, sobre cortes de placenta estudiando las subpoblaciones linfocitarias de las villitis, que el 50 por ciento eran CD4 (linfocitos helper), 18 por ciento CD8 (linfocitos supresoreslcitotóxicos) y 10 por ciento Leu19 (Natural Killer) pero lo significativo y anormal es que hallamos que el 65 por ciento de los linfocitos expresaban antígenos de histocompatibilidad clase II DR (40). En 1998 Jacques y Col publicaron datos similares. En 1999 comunicamos que en el informe histopatológico de material de legrado de pacientes abortadoras de causa inmunológica la descripción de villitis en un 20 por ciento de los casos. Estudios realizados en colabaración con la Dra. Zenclussen con ese material nos permitió publicar recientemente la presencia de altos niveles de Interleuquina 6(IL-6) y receptor de IL-6 en suero. El objetivo de este estudio es investigar en placentas de pacientes abortadoras recurrentes la expresión de IL-6 y sus receptores gp80 y gp130 en trece muestras de material de raspado de abortos del primer trimestre mediante la técnica de inmunofluorescencia. Como control se utilizaron cortes de placentas de embarazos normales a término. Nuestros hallazgos muestran la presencia de depósitos de IL-6 y de receptores de IL-6 con un patrón granular para las tres moléculas especificamente en el sinciciotrofoblasto mientras que fue negativo para tres en el citotrofoblasto. En los cortes de placentas normales no se hallaron en ningún caso dichos depósitos. Concluímos de todos los hallazgos antes sintetizados...(AU)

Interleukin-6 and soluble interleukin-6 receptor serum levels in recurrent spontaneous abortion women immunized with paternal white cells.

PROBLEM: Recurrent spontaneous abortion (RSA) could be interpreted as the cause for the incapacity of the mother to recognize paternal antigens to produce the desired protective response. The practise of alloimmunization was introduced in an attempt to induce in the mother the production of an alloimmune response; some authors proposed an association between cytokines and RSA. The production of IL6 and its soluble receptor (sIL6R) before and after lymphocyte immunotherapy was evaluated in sera of 33 patients suffering from two or more RSA, and in sera of 47 women with normal pregnancy. METHOD OF STUDY: The immunization of RSA patients was achieved by injection of four doses of 10(5) mononuclear cells (MNC) from the husband, at weekly intervals, before pregnancy. The IL6 and sIL6R levels were measured using sandwich ELISAs and the results evaluated by Tukey-Kramer multiple comparison-tests. RESULTS: Our data show no significant differences between IL6 and sIL6R serum levels of normal pregnant women and RSA pregnant women with white-cell immunization before pregnancy. In contrast, the sera of pregnant RSA patients without allogeneic therapy show higher values. We also found significant differences between IL6 levels in non-pregnant RSA women with and without immunotherapy. CONCLUSION: These results show that the alloimmunization with paternal white cells leads the serum IL6 and sIL6R-levels to the values observed in the course of normal pregnancy, suggesting a role for IL6 and sIL6R in the modulation of the immune response's quality.

Polymerase chain reaction reveals Trypanosoma cruzi infection suspected by serology in cutaneous and mucocutaneous leishmaniasis patients.

The existence of patients suffering a double infection caused by Trypanosoma cruzi and Leishmania spp. has been suggested by several authors. Since the conventional serological tests now available for the diagnosis of Chagas' disease lack specificity due to the cross-reactivity between these two parasites, a serological confirmation of a T. cruzi infection cannot be made unless specific antigens are used. An enzyme linked immunosorbent assay (ELISA) to detect antibodies against a specific T. cruzi antigen, named Ag163B6, and immunoblotting using T. cruzi epimastigotes, are non-conventional serological techniques that could be employed for specific diagnosis of Chagas' disease. Using these two methods 34 cutaneous or mucocutaneous leishmaniasis patients were classified into two groups: (A) patients with serological evidence of T. cruzi infection, i.e. those who tested positive in at least one assay (18/34); and (B) patients with no serological evidence of T. cruzi infection, i.e. those who were negative for both assays (16/34). Taking into account the difficulties of xenodiagnosis and its low sensitivity (less than 50%) for a direct diagnosis in the chronic period of the disease, we used polymerase chain reaction (PCR) to confirm a T. cruzi infection in those leishmaniasis patients who presented positive results with the non-conventional serological techniques. Of the 18 patients with serological evidence of T. cruzi infection, 17 gave positive results when genomic DNA primers were used. Using minicircle primers, 15/18 of that group were positive. Nevertheless, all the patients suspected of being double infected were positive in at least one PCR test. Just one patient with no serological evidence of T. cruzi infection gave a positive PCR result when amplifying the minicircle sequence. The proof of the existence of a T. cruzi infection by PCR in leishmaniasis patients suspected to be chagasic when non-conventional serology was used, strongly supports the use of the specific Ag163B6 and immunoblotting with epimastigotes as specific serological diagnostic tools to determine a T. cruzi infection.

Modulation of the immune response by progesterone-induced lymphocyte factors.

Rat spleen and peripheral blood lymphocytes express progesterone receptors whose concentration is increased greatly during the early phase of pregnancy. After stimulation of progesterone the expression of receptors was augmented 2-3 times. When cells were cultured in the presence of progesterone they released a soluble factor that inhibited cellular immunoreactions (MLR, CRC) and cellular proliferation as measured by thymidine incorporation by spleen-cell culture. This factor also inhibited the synthesis of anti-DNP antibodies by a mouse hybridoma and diminished the proportion of cells in phase S. However, the percentage of asymmetric molecules produced by the hybridoma remained unaltered. These results support the hypothesis that soluble factors released by rat lymphocytes modulate the immune response of the mother and participate in the mechanism that protects the fetus against antipaternal antibodies.

[Participation of transcriptional factors in the regulation of lymphocyte differentiation]. / Participación de factores de transcripción en la regulación de la diferenciación linfocitaria.

The cytomorphological changes as well as the expression of certain markers in the different stages of lymphocyte differentiation are well known. Studies carried out on expression patterns of specific genes in lymphoid cells and their regulatory mechanism have led to the identification of the fundamental mechanism of cell development and activation. A great deal of knowledge has accumulated concerning enhancers and promoters, the regulatory elements of those genes and the transcriptional factors to which they bind. The present paper analyzes these components and the participation of some of them such as PU.1, Ikaros, Aiolos, GATA-3, Egf-1, E2A, EBF-1, PAX-5 (BSAP), TFE-3, Oct-1, Oct-2, and Nf-kappa B in the regulation of the differentiation stages of cells belonging to the B and T lymphoid lineages.

Participación de factores de transcripción en la regulación de la diferenciación linfocitaria. / [Participation of transcriptional factors in the regulation of lymphocyte differentiation]

The cytomorphological changes as well as the expression of certain markers in the different stages of lymphocyte differentiation are well known. Studies carried out on expression patterns of specific genes in lymphoid cells and their regulatory mechanism have led to the identification of the fundamental mechanism of cell development and activation. A great deal of knowledge has accumulated concerning enhancers and promoters, the regulatory elements of those genes and the transcriptional factors to which they bind. The present paper analyzes these components and the participation of some of them such as PU.1, Ikaros, Aiolos, GATA-3, Egf-1, E2A, EBF-1, PAX-5 (BSAP), TFE-3, Oct-1, Oct-2, and Nf-kappa B in the regulation of the differentiation stages of cells belonging to the B and T lymphoid lineages.

Effect of pregnancy and placental factors on the quality of humoral immune response.

Asymmetrical IgG molecules are characterised by the presence of a mannose-rich oligosaccharide group in only one of the two Fab fragments, which impairs the corresponding paratope, causing such molecules to behave as univalent antibodies and therefore as antigen blockers [1-3]. During human and murine pregnancy, an increase has been detected in asymmetrical IgG molecules in serum and those bound to the placenta, which normally releases factors capable of modulating the immune response. It thus seemed of interest to investigate the effect of placental culture supernatants (PCS) on in vivo and in vitro synthesis of rat immunoglobulin IgG1, IgG2a, IgG2b and IgG2C, particularly the ratio of symmetrical and asymmetrical molecules in each isotype. The effect of PCS was determined in vivo by means of passive transfer to virgin females and in vitro by analysing the supernatants of spleen cells cultured in the presence of PCS. The results showed that neither pregnancy status nor PCS were capable of modifying serum levels of IgG2a, IgG2b or IgG2c, whereas the level of IgG1 was reduced. When PCS were added to the spleen cells cultures, an in vitro increase was observed in IgG2a, IgG2b and IgG2c production. The separation of symmetrical from asymmetrical IgG molecules was performed by affinity chromatography in Concanavalin A-Sepharose, as such lectin binds high mannose sugars present only in asymmetrical IgG molecules. It is shown that pregnancy and PCS induce an increase in IgG1 and IgG2 molecules asymmetrically glycosylated, capable of binding to ConA-Sepharose. Therefore, the placenta is capable of releasing factors which can regulate the relative proportion of asymmetrical IgG molecules and induce quantitative and qualitative modifications of the in vitro and in vivo produced antibodies.

Paradoxical behavior of asymmetric IgG antibodies.

Changes in the quantity and quality of antibodies occur in the course of an immune response. This review describes the physicochemical and biological properties of asymmetric antibodies as well as their functions, beneficial or harmful to the host, according to the nature of the antigen and the particular situation in which they act. Asymmetric antibodies have two paratopes, one of high affinity, with K0 similar to that of symmetric antibodies, and the other one with an affinity for the antigen 100 times lower. Functional univalence is due to steric hindrance present in one of the paratopes by the carbohydrate moiety attached to the Fd fragment of the Fab region, so these antibodies are unable to form large antibody-antigen complexes and cannot trigger reactions, such as complement fixation, phagocytic activity and antigen clearance. When asymmetric IgG antibodies are specific for self-antigens, they prove beneficial for the host by exerting regulatory functions. In allergic manifestations, in autoimmune diseases and especially during pregnancy, despite the fact that the antigens responsible for the process are foreign to the host, they also perform beneficial activity. During pregnancy, the placenta secretes molecules or factors that regulate the synthesis of these antibodies, thus favoring fetal protection.