Gillian M.P. Galbraith

The human materno-foetal relationship in malaria. II. Histological, ultrastructural and immunopathological studies of the placenta

Histological and ultrastructural studies of four placentae heavily infectd with Plasmodium falciparum revealed large intervillous accumulations of erythrocytes containing parasites together with monocytes which had ingested pigment. These appearances were associated with focal syncytial necrosis, loss of syncytial microvilli and proliferation of cytotrophoblastic cells. In addition, marked irregular thickening of trophoblastic basement membranes and protrusion of tongue-like projections of syncytiotrophoblast into the basement membrane were observed. In six other placentae which contained scanty amounts of pigment but no parasites, representing past or inactive infection, no large collections of monocytes or abnormalities of trophoblast were apparent but basement membrane thickening was evident. Immunohistological studies revealed no significant differences between placentae positive for parasites and those containing pigment only, although the amount of certain immunoproteins and clotting factors was clearly increased above normal. These findings establish that P. falciparum infection in the placenta may result in substantial damage although lesions within the villus are rare. Furthermore, previous infection, although adequately controlled, may leave a heritage of pigment deposition, basement membrane thickening and immunopathological lesions. These results may thus account for both the high frequency of intra-uterine growth retardation and the rarity of congenital malaria in the presence of P. falciparum malaria.

Tumor necrosis factor alpha (TNF-α) gene polymorphism in alopecia areata

Tumor necrosis factor alpha (TNF-α) phenotypes of two polymorphic systems were determined in 50 patients with alopecia areata, a common inflammatory disease of the skin. The distribution of TNF-α T1, T2 phenotypes differed between patients with the patchy form of disease and patients with totalis/universalis disease. There was no significant difference in the distribution of TNF-α G,A phenotypes between patient groups. The results of this study provide evidence of genetic heterogeneity between the two forms of alopecia areata, and suggest that the TNF-α gene or a closely linked locus within the major histocompatibility complex may play a role in the pathogenesis of the patchy form of disease.

Transferrin binding by human lymphoblastoid cell lines and other transformed cells

Abstract Viable cells of 18 human cell lines, including 15 transformed cell lines of malignant and lymphoblastoid origin, were examined by an indirect immunofluorescence method for their ability to bind purified transferrin and transferrin in normal human serum. The specificity of the reaction was investigated by study of the binding reactions of several other serum proteins, including albumin, α-1-antitrypsin, and α-2-macroglobulin. Membrane binding of human transferrin was demonstrated in less than 5% of normal peripheral blood mononuclear cells or cultured diploid fibroblasts, but in more than 80% of the cells from 13 of the transformed lines, and the data obtained indicated that this binding reaction reflected the presence of specific receptors for transferrin.

Trophoblast Transferrin and Transferrin Receptors in the Host-Parasite Relationship of Human Pregnancy

Transferrin and specific transferrin receptors are demonstrated on the microvillous surface of syncytiotrophoblast in human immature and term placentae by immunohistological techniques with the use of light and electron microscopy. That the distribution of transferrin is limited to the materno-foetal interface supports the hypothesis that binding of maternal transferrin to trophoblast receptors is involved in the process of iron transport to the foetus. Parallel studies with baboon placentae demonstrate the presence of trophoblast receptors which bind both baboon and human transferrin, thereby putting forward an experimental model which might be used to test the biological significance of placental transferrin receptors in primates. In addition, investigation of a large number of human cell lines shows that many transformed cells, but no normal cells (such as blood lymphocytes) or cells from primary culture (such as neonatal foreskin fibroblasts), possess the ability to bind transferrin to their membranes. These findings suggest that transferrin receptors may play important biological roles in addition to that of iron transport from mother to foetus. One such role could be the limitation of iron in intervillous spaces, thus depriving iron-requiring microorganisms of iron, hence serving as a non-specific factor of resistance for placentae. Another role for foetal transferrin receptors on trophoblasts could be to bind maternal transferrin at the materno-foetal interface, thus frustrating maternal immunosurveillance. This is similar to a mechahism used by schistosomes in the host-parasite relation where host proteins are bound by the parasite to escape immunological recognition. The presence of transferrin receptors on transformed cells suggests that this mechanism might also be employed by tumour cells. Finally, in view of previous studies which show that transferrin is required by stimulated lymphocytes to pass from the G1 to the S phase of cellular replication, it is proposed that trophoblast transferrin receptors could limit the amount of transferrin in intervillous spaces and thus impede the proliferation and possible cytotoxicity of maternal activated lymphocytes at the materno-foetal interface.

Transferrin binding to peripheral blood lymphocytes activated by phytohemagglutinin involves a specific receptor. Ligand interaction.

Immunohistological studies have indicated that membrane sites binding transferrin are present upon activated human peripheral blood lymphocytes. In this study, we have investigated transferrin uptake in human lymphocytes exposed to phytohemagglutinin (PHA), by quantitative radiobinding and immunofluorescence in parallel. In stimulated lymphocytes, binding was maximal after a 30-min incubation, being greatest at 37 degrees C, and greater at 22 degrees C than at 4 degrees C. Although some shedding and endocytosis of transferrin occurred at 22 degrees and 37 degrees C, these factors, and resulting synthesis of new sites, did not affect measurement of binding which was found to be saturable, reversible, and specific for transferrin (K(a) 0.5-2.5 x 10(8) M(-1)). Binding was greater after a 48-h exposure to PHA than after 24 h, and was maximal at 66 h. Sequential Scatchard analysis revealed no significant elevation in affinity of interaction. However, although the total number of receptors increased, the proportion of cells in which binding of ligand was detected immunohistologically increased in parallel, and after appropriate correction, the cellular density of receptors remained relatively constant throughout (60,000-80,000 sites/cell). Increments in binding during the culture period were thus due predominantly to expansion of a population of cells bearing receptors. Similar differences in binding were apparent upon comparison of cells cultured in different doses of PHA, and in unstimulated cells binding was negligible. Transferrin receptors appear, therefore, to be readily detectable only upon lymphocytes that have been activated.

Immunological profiles in alopecia areata

Cell‐mediated immunity and auto‐immune phenomena were investigated in sixty patients with active alopecia areata of various degrees of severity. Serum auto‐antibodies to thyroid antigens were detected in twenty‐three patients. Examination of T‐lymphocyte populations, lymphocyte DNA synthesis, and lymphokine production in response to mitogen stimulation revealed no differences between the sixty patients and matched healthy control subjects. However, patients with thyroid auto‐immunity and/or the presence of alopecia totalis or universalis showed significant reductions in interactive T lymphocytes (recognized by rosette formation with human B lymphoblastoid cells) and diminished production of leukocyte migration inhibition factor in response to stimulation with phytohaemagglutinin. This suggests that immune mechanisms may be involved in the pathogenesis of alopecia areata which is associated with thyroid auto‐immunity or which progresses to total hair loss.

The human materno-foetal relationship in malaria: I. Identification of pigment and parasites in the placenta

To facilitate investigations of the consequences of malarial infection during human pregnancy, several methods for the recognition of pigment and parasites in the placenta were evaluated. Pigment was visualized in infected blood smears and placental tissue using both white light and modified fluorescence microscopy. However, the characteristic pigment dots observed with fluorescent light were also apparent in unstained cryostat and deparaffinized placental sections, and following reaction with immunohistological reagents. Intact parasites were recognized immunohistologically in placental sections and blood smears using rabbit antisera to Plasmodium falciparum and P. berghei. Using these procedures, numerous erythrocytes containing parasites associated with small pigment dots were seen in intervillous spaces in heavily infected placentae. In these organs, larger irregular pigment aggregates were present within maternal cells which were shown to be monocytes by esterase staining. Pigment was also observed in the cytoplasm of the trophoblast and not infrequently in the mesenchymal stroma, but no intact parasites were observed within chorionic villi. These simple and sensitive methods thus confirm placental localization of parasites and pigment. Furthermore, the finding of pigment in all Gambian placentae examined, of which seven were thought initially to be uninfected, indicates that malaria may complicate pregnancy more frequently than hiterto anticipated.

Immunological studies of transferrin and transferrin receptors of human placental trophoblast

In primate pregnancy, fetal iron is derived from maternal transferrin; however, the mechanisms by which iron is taken up by the human placenta have not yet been established. In the present study, transferrin was demonstrated on the microvillous surface of human trophoblast in immunohistological studies of 130 mature and immature placentae from both normal and abnormal pregnancies. Similar results were found for baboon placentae. Upon short-term culture of placental tissue, the amount of trophoblast transferrin decreased and no incorporation of 14C lysine into transferrin could be detected by radioimmunoelectrophoresis. Thus this transferrin apparently was not synthesized by the placenta. When transferrin was removed from cryostat sections of placenta by treatment with chaotropic agents, subsequently added transferrin bound in an identical distribution. The specificity of this reaction was confirmed by the lack of binding of other serum proteins and by displacement procedures in which trophoblast transferrin was shown to be dislodged by transferrin added in vitro. These findings suggest that placental iron transport is predicated by binding of transferrin to specific receptors on trophoblast.

Differential Anatomical Expression of Transplantation Antigens Within the Normal Human Placental Chorionic Villus

ABSTRACT: The expression of transplantation antigens by cells of the placenta was examined by immunohistological and immunoprecipitation procedures with defined conventional and monoclonal antisera to beta2‐microglobulin, DR and DC gene products, and H‐Y antigen. Cells of the mesenchymal stroma within chorionic villi were positive by immunofluorescence for major histocompatibility complex antigens, and in male pregnancies for H‐Y antigen, but the trophoblast was consistently negative for all antigen systems examined. Immunohistological examination of viable suspensions of cultured diploid trophoblast and of isolated membranes also gave negative results, and after radioiodination and solubilization of membranes, no detectable radioactive material was immunoprecipitated. These results provide further evidence that transplantation antigens are not expressed by human trophoblast. Since this is a fetal structure exposed directly to immunologically competent cells of the mother in the intervillous spaces, this observation may be relevant to the apparent lack of damaging maternal immune responses directed against the fetal homograft.

Partial restoration of impaired interleukin-2 production and Tac antigen (putative interleukin-2 receptor) expression in patients with acquired immune deficiency syndrome by isoprinosine treatment in vitro.

The in vitro effects of isoprinosine (ISO) on interleukin-2 (IL-2) production, the expression of Tac antigen (IL-2 receptor) on lymphocytes, and the ability of Leu 3(+) cells to absorb interleukin-1 (IL-1) were investigated in 10 patients with acquired immune deficiency syndrome (AIDS). In 9 of the 10 patients, production of IL-2 from mononuclear cells and Leu 3(+) cells was depressed; expression of Tac antigen on mononuclear cells and Leu 2(+) cells was found to be depressed in 9 of 10 patients. The ability of the Leu 3(+) lymphocytes to absorb IL-1 was depressed in all (four of four) patients studied. After ISO treatment, IL-2 production, Tac antigen expression and IL-1 absorption were restored to normal or near normal levels in most of the patients. These results suggest that ISO has an immunostimulating capacity in AIDS patients and that the potential of ISO in immune response restoration in AIDS patients deserves critical consideration.