Ovine placental eluate immunoglobulins recognise isologous and third party acid-treated trophoblast microvesicle antigens in vitro.

Placental microvesicles were prepared from ovine placentae and immunoglobulins eluted with 0.5 M glycine buffer pH 2.5. The ability of eluate immunoglobulins to re-associate with isologous (self) and third party acidified microvesicles was tested by ELISA. Ovine placental immunoglobulins re-associated with isologous and third party acidified microvesicles suggesting that at least 2 types of antigenic epitopes I and II maybe expressed on the ovine placentae. Type I antigens may be present on placentae of all ovines while type II epitopes may be paternally derived, hence unique to each pregnancy. Analysis by SDS PAGE revealed the heavy and light chains of IgG at 57 and 27 kDa, respectively, together giving a relative molecular weight of 158 kDa. Results suggest that immunoglobulins produced to placental microvesicle antigens may be directed to some but not all antigenic epitopes expressed on the trophoblast, possibly defining a mechanism by which the foetus evades maternal immunological rejection.

Human placental immunoglobulins show unique re-association patterns with isologous and third party acid treated trophoblast microvesicles in vitro.

OBJECTIVE: To study re-association pattern of human placental eluate immunoglobulins with acid treated isologous and third party trophoblast derived placental microvesicles. DESIGN: Laboratory based experimentation. SETTING: Biological Sciences Department and Discipline for Reproductive Medicine University of Newcastle, Australia and the Department of Biochemistry, University of Nairobi, Kenya. RESULTS: Placental eluate immunoglobulins re-associated with isologous and third party acidified microvesicles in three distinct patterns. I: eluate immunoglobulins re-associated more strongly with isologous and third party acid treated placental microvesicles, II: eluate immunoglobulins re-associated strongly with isologous but weakly with third party acid treated placental microvesicles, III: eluate immunoglobulins did not show preferential re-association with isologous and third party acid treated placental microvesicles. CONCLUSION: Two types of antigenic epitopes I and II may be expressed on the human placentae. Type I antigens may be present on all human placentae while type II epitopes may be paternally derived hence unique to each pregnancy. Also, immunoglobulins produced to placental microvesicle antigens may be directed to some but not all antigenic epitopes expressed on the human placental trophoblast.

Immunoglobulin G bound to ovine placenta is eluted by surgical cannulation and acid perfusion in situ.

OBJECTIVE: To elute placental bound immunoglobulin G (IgG) in situ. DESIGN: Laboratory based experimentation. SETTING: Biological Sciences Department, The University of Newcastle Australia and the Department of Biochemistry, University of Nairobi, Kenya. SUBJECTS: Twelve pregnant ewes 10 to 15 days before the onset of natural parturition. RESULTS: Placental eluates were rich in IgG, and IgG2. The relative molecular weight of placental IgG was estimated at 158kDa by gel filtration chromatography. Analysis of eluate by SDS PAGE revealed the heavy and light chains of IgG at 57 and 27kDa respectively together giving a relative molecular weight of 168kDa. CONCLUSION: Placental bound IgG may be crucial in immunology of pregnancy and together with the cognate antigen thereof may be useful as models for the study of maternal-fetal interaction in human pregnancy and in the development of experimental immunotherapy to immunologically compromised pregnancies in humans and livestock.

Cellular and molecular interactions in HIV infections: a review.

OBJECTIVE: To review the cellular and molecular interactions between HIV and the host immune system that lead to full-blown AIDS. DATA SOURCES: Published reports on HIV/host interaction during a fifteen year period beginning from 1987. STUDY SELECTION: Only those studies involving humans and non-human primates were selected. The studies included original articles and state-of-the-art reviews covering in vivo and in vitro findings. DATA EXTRACTION AND SYNTHESIS: This article presents a critical review of the cellular and molecular mechanisms of HIV infection and their relationship to the onset of AIDS. CONCLUSION: HIV has elaborated diverse and somewhat complicated mechanisms for the subversion and evasion of the host immune defence strategies. These include escape through mutation, prolonged latency of the infection, masking of the viral envelope proteins, down-regulation of MHC-I and up-regulation of the Fas-ligand on infected cell surfaces. This review enhances our understanding of HIV/AIDS disease and presents a basis on which management strategies could be developed.

Biomedical challenges of human senescence: a review.

OBJECTIVE: To summarise and discuss the progress made in the study of human senescence over the past one hundred years and assess the achievements to date. DATA SOURCES: Published original research and reviews during the past one hundred years. STUDY SELECTION: The summary focused on those contributions that tested the various hypotheses that attempt to identify and explain the factors that are involved in the ageing process. DATA EXTRACTION AND SYNTHESIS: Online and manual library searches provided a body of data on which the summaries and discussions were based. Specific questions were addressed: Why does ageing occur? What are the key mechanisms? To what extent are genetic and environmental factors involved in the ageing process? How does the immune system behave during ageing and especially against infectious agents? Answers to these questions were discussed against the background of major improvements in life expectancy in most parts of the world except for sub-Saharan Africa where the HIV/AIDS pandemic has reversed the trend. CONCLUSION: Biological and clinical studies over the past century clearly reflect a better understanding of the major factors involved in human senescence. It is appreciated that human life expectancy has improved dramatically over the period through achievements in public health, therapy, nutrition and general living standards. A great deal remains to be done through multidisciplinary research before the quality of life can be improved further.

Possible immunological basis for recurrent spontaneous abortions: a review.

BACKGROUND: In normal pregnancy, the pregnant mother paradoxically tolerates the semi-allogeneic foetus until term. Experimental and clinical data to explain such tolerance in man reflects the involvement of multiple mechanisms. OBJECTIVE: To review the data pertaining to the experimental and clinical efforts to explain why the mother immunologically tolerates a semi-allogeneic pregnancy to term. DESIGN, SETTING AND METHODS: A review of the literature on state of the art thinking among researchers and clinicians on recurrent spontaneous abortions is summarised. RESULTS: A large body of recently published data strongly suggest that a breakdown in immunological maternal-foetal interactions may lead to occasional or recurrent foetal loss. Immunoregulatory activities involving blocking antibodies, regulatory factors, immunological cells, hormones, structural proteins and cytokines constitute the pregnancy-sustaining network. CONCLUSION: The majority of the evidence reviewed points to the involvement of immunological factors in successful pregnancies. However, the underlying mechanisms are inadequately explained, are largely speculative and require more focused investigation. A complete understanding of the mechanisms involved would enhance our capacity to develop rational ways of addressing recurrent pregnancy losses.

Immunological Role of the Placenta, Blocking Factors and NK Cells in Post-implantation Pregnancy.

The unexpected failure of the mother to immunologically reject the foetus is partly thought to result from immunological properties of the placenta. The placental trophoblast produces immunosuppressive factors including progesterone and blocking antibodies which together down-regulate maternal immune responses to the foetoplacental unit. This article reviews the post implantation immunology of pregnancy emphasizing the roles of placenta, blocking factors and natural killer (NK) cells.

Ovine and Human Placental IgG inhibit Human Natural Killer Cell Cytotoxicity in vitro.

To determine the effect of ovine and human placental IgG on human Natural Killer (NK) cell cytotoxicity in vitro placental IgG was eluted at acidic pH and purified by ion exchange and subsequently by affinity chromatography on protein G and protein A sepharose columns. These antibodies were analysed for presense of IgG by immuno-electrophoresis and relative purity determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS PAGE). The effect of these antibodies on human NK cell cytotoxicity was investigated by slChromium Release Assay using human K562 cells as targets and human peripheral blood lymphocytes as effector cells. Both ovine and human placental IgG inhibited human NK cell cytotoxicity in a dose dependent manner. Placental IgG may down-regulate the cytotoxic effects of NK cells in vivo by competitively excluding the binding of NK cells to their respective targets on the trophoblast. Alternatively, these antibodies may themselves be toxic to NK cells. Either way, the presence of these antibodies on the placental trophoblast may prevent the binding of NK cells and subsequent immunological rejection of the fetal allograft. Also, ovine placental IgG may be functionally similar to its human counterpart and may therefore be suitable as a model for the study of maternal fetal interaction during pregnancy in humans.

Recurrent pregnancy losses and the role of immunotherapy.

Post implantation pregnancy losses are psychologically and economically stressful to the childbearing population. The etiology in the vast majority of cases is unknown but is partly thought to result from a break-down of the maternal tolerance to the fetoplacental unit. Immunologically based therapy remains controversial but no alternative therapy is available at the moment. This article reviews the conceived immunological basis of recurrent pregnancy losses, discussing the controversies arising, and recommending the use of intravenous immunoglobulin, IVIg, in well controlled experiments for further clinical trials.

Poverty reduction and the HIV / AIDS epidemic in Kenya:What are the core issues.

The government of Kenya has recently attempted to develop a national budget that gives priority to two pertinent constraints to national development efforts. These are poverty and HIV/AIDS. The poor are those members of society that are unable to afford minimum basic human needs comprising food and non-food items. Slightly over 50% of Kenyans live bellow poverty line. Also, about 700 Kenyans are lost to the HIV/AIDS epidemic everyday. 75% of those infected live in the rural areas and the majority of those are aged 15-39 years. Any efforts to reduce poverty and contain the epidemic will require an integrated approach because of the interplay between the effects of HIV/AIDS and poverty. Both poverty and HIV/AIDS are direct, non-selective and universal, both affects males, females and children ,reduce the labour force as well as food production, strain medical services and generally aggravate the performance of the economy. There is therefore an absolute need to protect the poor from infection and re-infection especially those located in the rural areas and the youth who are at risk. An essential component of this protection is public education of these groups, accompanied by economic empowerment through creation of self-employment opportunities. The recently developed Poverty Reduction Strategy paper (PRSP) clearly identifies these lines of attack. What remains is the translation of these noble ideas into concrete implementable projects and programmes with the participation of all stakeholders.

Purification and partial characterisation of goat placental IgG: A possible model for the study of human maternal-foetal interaction.

Viviparous pregnancy in vertebrates is a major immunological puzzle. Ideally the maternal immune system should reject the foetus, which is antigenically different by virtue of its compliment of paternal genes and proteins. Instead the mother accommodates the foetus until term. This is partly thought to result from production of blocking antibodies, down regulation of the maternal immune responses and existence of a placental barrier among others. This report presents findings that antibodiess exist on goat placentae that could hypothetically block rejection of the fetal allograft. The total obtainable placental IgG was approximately 110Ug per term placenta. Analysis of eluate antibodies by SDS PAGE showed that placental IgG is approximately 214.4kDa and had a pI of 6.02. Trypsin digestion of acidified plantal microvesicles led to release of a 53kDa peptide similar to one reported earlier in humans. This observation suggest that certain placental proteins may be conserved across the mammalian species for reproductive purposes. We propose that goat placental IgG may be useful as a model for the study of maternal-foetal interaction during pregnancy.

Purification and Partial Characterization of Goat Placenta IgG : a Possible Model for the Study of Human Maternal-Foetal Interaction

Viviparous pregnancy in vertebrates is a major immunological puzzle. Ideally the maternal immune system should reject the foetus; which is antigenically different by virtue of its compliment of paternal genes and proteins. Instead the mother accommodates the foetus until term. This is partly thought to result from production of blocking antibodies; down regulation of the maternal immune responses and existence of a placental barrier among others. This report presents findings that antibodiess exist on goat placentae that could hypothetically block rejection of the fetal allograft. The total obtainable placental IgG was approximately 110Ug per term placenta. Analysis of eluate antibodies by SDS PAGE showed that placental IgG is approximately 214.4kDa and had a pI of 6.02. Trypsin digestion of acidified plantal microvesicles led to release of a 53kDa peptide similar to one reported earlier in humans. This observation suggest that certain placental proteins may be conserved across the mammalian species for reproductive purposes. We propose that goat placental IgG may be useful as a model for the study of maternal-foetal interaction during pregnancy

Purification and characterization of an anticoagulant from the salivary glands of the ixodid tick Rhipicephalus appendiculatus.

An anticoagulant isolated from salivary gland extracts of the ixodid tick Rhipicephalus appendiculatus was purified by gel filtration on Sephadex G-100, ion exchange on DEAE-cellulose, aprotinin-Sepharose, and by high-pressure-liquid size-exclusion chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the anticoagulant activity was associated with a protein of an apparent Mr of 65 kDa. The purified molecule had a pI in the range of 8.0-8.5 on chromatofocusing and was stable over a wide pH range, but was heat labile and susceptible to inactivation by trypsin and reductive alkylation. The anticoagulant did not inhibit thrombin-initiated fibrin formation and had no detectable fibrino(geno)lytic or phospholipase-like activities. Although it inhibited factor Xa-induced clotting of bovine plasma, it did not affect the amidase activity of factor Xa toward a synthetic substrate, suggesting that the anticoagulant acts at a site distinct from the active site of factor Xa or on other components of the prothrombinase complex.

Cell-mediated immunity to spermatozoal antigens after vasectomy: recent developments.

PIP: Vasectomy has rapidly become the most popular male sterilization technique in man in recent years. However, little is known about its long-term physiological, anatomical, endocrinological, and immunological consequences. This report summarizes recent developments in investigations into the immune response to spermatozoa after vasectomy. The review deals with those aspects that bear directly on clinical problems. Animal data is used where necessary to supplement inadequate knowledge of events occurring in man. The review reveals that the main obstacles to major progress in this area of research include: 1) unavailability of purified sperm antigens, 2) unavailability of a suitable animal model for such studies, and 3) inadequacy of the techniques currently in use. These are suggested as major avenues for future exploration.^ieng