Histocompatibility antigens, transferrin receptors and extra-embryonic markers of human amniotic epithelial cells in vitro

Amniotic membrane surgery

Human amniotic membrane (AM) is composed of three layers: a single epithelial layer, a thick basement membrane, and an avascular stroma. Amniotic membrane has anti-adhesive properties and is felt to promote epithelialization and decrease inflammation, neovascularization, and fibrosis. Amniotic membrane transplantation (AMT) is currently being used for a continuously widening spectrum of ophthalmic indications. Amniotic membrane transplantation has been shown to be effective in the reconstruction of the corneal surface in the setting of persistent epithelial defects, sterile corneal ulcerations, and partial limbal stem cell (LSC) deficiency states, including those secondary to chemical or thermal burns. Amniotic membrane transplantation also has been used in conjunction with limbal stem cell transplantation (LSCT) both in a concurrent fashion as well as in preparation for LSCT. Amniotic membrane transplantation also has been used in place of conjunctival autografting after pterygium excision and to reconstruct the conjunctival surface after removal of conjunctival lesions. Most recently, ex vivo cultivation and expansion of limbal epithelial cells has been performed utilizing AM as a matrix. However, the superiority of AMT over other treatment modalities in many of these settings needs to be substantiated by controlled clinical trials.

Monoclonal antibody GB24 recognizes a trophoblast-lymphocyte cross-reactive antigen

GB24 is a mouse monoclonal antibody (IgG1) raised against human term placental microvilli. This antibody displayed pan-trophoblast reactivity pattern. In addition, GB24 recognized normal peripheral leukocytes and transformed cell lines (Daudi, HL-60, Jurkat, AV3, BeWo, HT-29) by using membrane immunofluorescence and flow cytometry. By SDS-polyacrylamide gel electrophoresis, this antibody immunoprecipitated two proteins of 62 kilodaltons (kDa) and 75 kDa from placental microvilli. Isoelectrofocusing analysis revealed that these two bands exhibited different isoelectric points: 4.7 for the 62 kDa protein, 4.6 and 4.4 for the two spots corresponding to the 75 kDa protein. Microvilli from different placentae revealed substantial differences regarding the intensity of the labeling of these two bands, suggesting that the antigens recognized by GB24 are probably allotypic.

Monoclonal antibodies (GB16, GB18, GB19, GB22) raised against human placental microvilli recognize the transferrin receptor

GB16, GB18, GB19 and GB22 are mouse monoclonal antibodies produced against full-term human placental microvilli. These antibodies reacted predominantly with the apical surface of the syncytiotrophoblast from first-trimester and full-term placentae, and also reacted with several cell lines derived from non-haematopoietic tissues by immunofluorescence. The radioiodinated BeWo (choriocarcinoma) cell surface proteins were immunoprecipitated with these four antibodies and analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The results demonstrated that the immunoprecipitates migrated at 180 and 90 kilodaltons under non-reducing and reducing conditions, respectively. Using enzyme-linked immunosorbent assay, the antigens recognized by GB16, GB18, GB19, and GB22 were able to bind human transferrin. Immunoabsorption studies showed that these four antibodies bound to the same molecule as OKT9, an antibody to the transferrin receptor. Moreover, the reactivities of these antibodies with HL-60 (promyelocytic leukaemia) cells diminished following dimethyl sulphoxide-induced differentiation by flow cytometric analysis. These data indicate that these four antibodies recognize the transferrin receptor. By competition assay, GB18 bound to an epitope different from those recognized by GB16, GB19 and GB22. In addition, GB22 displayed significant growth inhibition against the activated lymphocytes and Daudi cells, but not against HL-60 or Jurkat cells. These data suggest that these four monoclonal anti-transferrin receptor antibodies will provide additional means to investigate the physiological roles played by the transferrin receptor.

Monoclonal antibody GB25 recognizes human villous trophoblasts

A monoclonal antibody GB25 which was raised against placental syncytiotrophoblast reacted specifically with villous trophoblasts. It recognized syncytiotrophoblast, villous cytotrophoblasts of the first-trimester placentae, and a majority of the cytotrophoblasts in the chorion laeve, but not the residual cells of cytotrophoblastic shell in the basal plates and the cells in the cytotrophoblastic columns. This antibody will be useful for isolating and differentiating villous from extravillous cytotrophoblasts in the first-trimester placentae.

Normal epithelial antigens recognized by GB3 and GB5 are diminished in intraductal and lost in infiltrating human breast carcinomas

GB3 and GB5 are mouse monoclonal antibodies raised against human amnion. GB3 detects the epidermal basement membrane, and GB5 reacts with the junctional substances between the epithelial cells. These two antibodies were studied on breast tissues by indirect immunofluorescence. All (n = 8) of the normal mammary glandular basement membranes and epithelia reacted strongly with GB3 and GB5. In the intraductal carcinomas (n = 10), although nine out of ten tissues were reactive, their reactivities were greatly reduced. More strikingly, in the infiltrating carcinomas (n = 15), none of the tumor specimens were recognized by GB3 and only one out of fifteen biopsies was moderately reactive with GB5, indicating that the syntheses of the antigens of GB3 and GB5 were discontinued in the metastatic breast adenocarcinomas. These data suggest that these antigens may contribute to the interaction of the epithelium with the extracellular matrix and the intercellular binding between the epithelial cells; the loss of these antigens may facilitate the wide dissemination of tumor cells.

Monoclonal antibodies to human amnion

Mouse hybridoma cell lines secreting monoclonal antibodies to human amnion were established. The reactivities of eight of these monoclonal antibodies (GB1, GB3, GB4, GB5, GB6, GB9, GB10 and GB11) on human skin and term extra-embryonic tissues, which included reflected amniochorions, basal plates, placentae, chorionic plates and umbilical cords, are reported. GB1, GB4, GB5, GB6, GB9 and GB11 showed various reactivity patterns on the epithelial cells of amnion, chorion and skin at different stages of differentiation. In addition, GB9 and GB11 showed extracellular reactivities; GB9 detected chorionic villi which were usually surrounded by fibrinoid and GB11 reacted with fibrinoid structures in the placentae and chorion laeve. GB10 recognized connective tissues in fetal mesenchyme and adult dermis. This study demonstrates the expression of many shared antigens between tissues derived from the extra-embryonic ectoderm and adult skin. These monoclonal antibodies will provide useful tools for further investigations of epithelial differentiation and transformation.

Characterization of antibodies to antigens of the human amnion

The specificities of antisera produced in nine rabbits to seven different preparations of human amniotic epithelium and controls were studied by immunofluorescence on cryostat sections of human amniochorions, placentae and a large collection of other tissues. Three different groups of reaction patterns were identified with the use of these antibodies, indicating the presence of at least three antigenic groupings which have been tentatively designated as amnion antigens 1 (AA1), amnion antigens 2 (AA2) and amnion antigens 3 (AA3). The AA1 group was found on the ectodermal tissues of breast ductal and corneal epithelium as well as on Hassall's corpuscles, while the AA2 group was also found on breast ductal and corneal epithelium and basal keratinocytes, but not on Hassall's corpuscles. The AA3 group was found on basement membranes of ectodermally derived epithelium, but was negative on kidney. The identification of the distribution of antigens in common with ectodermal tissues and extra-embryonic membranes suggests that human amnion and chorion may have a close embryological relationship with embryonic ectoderm and its subsequent products of organogenesis.

Cells of the fetomaternal interface: their role in the maintenance of viviparous pregnancy

An immune system capable of discriminating between self and nonself evolved in nature long before the appearance of the viviparous mode of pregnancy, which brings maternal cells into a direct physical contact with genetically disparate cells of fetal origin. In the hemochorial type of placentation, the former include cells of the maternal immune system. This article briefly reviews the possible mechanisms that may protect the semiallogeneic conceptus in nature, with special reference to the role of the cells at the fetomaternal interface. We also present some new data on the antigenicity of pre- and postimplantation trophoblast cells and the immunobiology of decidual cells. Systemic changes in the maternal immune system appear to represent homeostatic responses to the presence of a semiallogeneic conceptus, unrelated to its protection; mechanisms for this protection must reside locally at the fetomaternal interface. We find that the lack of immunogenicity of the outer (trophoblast) cells of the preimplantation blastocyst can be explained by a transient disappearance of the major histocompatibility (MHC) antigens on their cell surface. However, following implantation and the formation of the placenta, class 1 MHC antigens reappear on certain classes of trophoblast cells, i.e., labyrinthine and spongiotrophoblast cells of the murine placenta. Similarly, cytotrophoblast cells of the early human placenta exhibit the presence of class 1 MHC antigens. An absence of class 2 MHC antigens despite the presence of class 1 antigens cannot entirely explain the lack of trophoblast immunogenicity. A local immunosuppression mediated by trophoblast cells themselves as well as maternal cells of hemopoietic origin in the decidua remain as a strong possibility. Typical decidual cells appear to play a central role in the maintenance of pregnancy because of their numerous functions: nutritive, endocrine, and immunoregulatory. Our studies reveal that they are descendants of bone-marrow-derived precursors, have unique surface markers recognizable with monoclonal antibodies nonreactive with other hemopoietic cell lineages, and have the ability to abrogate mixed lymphocyte reactions in vitro in a genetically unrestricted manner. Further studies directed at the cells of the fetomaternal interface should provide a better insight into the mode of survival of the nature's most commonplace allograft.

Transferrin binding by peripheral blood mononuclear cells in human lymphomas, myelomas and leukemias

Significantly more peripheral blood mononuclear cells (PBM) from 39 patients with lymphoma (p less than 0.001), myeloma (p less than 0.001), or leukemia (p less than 0.001-0.025) bind transferrin (Trf) than those of 23 normals. That Trf was bound to a receptor on these cells was shown by the inhibition of these cells bound to 125I-Trf with unlabeled Trf. The paucity of Trf receptors on PBM from normals and their presence on diseased cells prompt a suggestion that Trf receptors may offer a useful approach to the diagnosis and possible treatment of some blood dyscrasias.