Gillian B. Dealtry

The Th2 Cytokine Environment of the Placenta

It is now accepted that local changes to the balance of Th1/Th2-type cytokines occur during pregnancy within the maternal uterus and fetoplacental unit. These changes in cytokine profiles contribute to implantation of the embryo, development of the placenta, and survival of the fetus to term. Overall within the placenta there is a bias in the ratio of Th1:Th2 cytokines towards the Th2-type cytokines. However, there are specific fluctuations in this balance at implantation and during the initiation of parturition. The predominant cytokines at each stage of gestation function both to limit maternal immune rejection of the semi-allogeneic embryo/fetus, especially at the maternofetal interface; and to facilitate the on-going physiological processes within the maternal reproductive tract. These two, at times conflicting, roles are discussed in this review, with key evidence concerning cytokine expression and function from mouse and humans.

Expression and localization of the Th2-type cytokine interleukin-13 and its receptor in the placenta during human pregnancy

PROBLEM: To investigate the expression of the Th2‐type cytokine interleukin (IL)‐13 and its receptor in human placenta during gestation.

Preimplantation mouse embryos express Mhc class I genes before the first cleavage division

We have used oligonucleotide primers complementary for polymorphic regions of the mouse H-2D gene in a highly sensitive polymerase chain reaction (PCR) assay to detect the transcription of maternal and paternal class I mRNAs in gametes and preimplantation embryos. Using congenic strains of mice differencing only at the major histocompatibility loci, class I (H-2D) mRNA of both the maternal and paternal haplotypes was demonstrated in embryos from the one-cell zygote to the late blastocyst stage of development but could not be detected in vas deferens or in vitro capacitated sperm or in ovulated secondary oocytes. These data clearly show that both paternally and maternally inherited Major histocompatibility complex (Mhc) class I genes are transcribed from the earliest stages of embryonic development, and suggest that developmental regulation of expression of their protein products is principally at the post-transcriptional level.

An Impaired Breeding Phenotype in Mice with a Genetic Deletion of Beta-2 Microglobulin and Diminished MHC Class I Expression: Role in Reproductive Fitness

Abstract Beta-2 microglobulin (B2M) plays a pivotal role in the biology of mammals, including its association with major histocompatibility complex (MHC) Class I gene products. The latter molecules have been shown to affect reproduction in both mice and humans, although the exact mechanism is still unknown. Here we report the results of a longitudinal study of the reproductive performance of a genetically modified B2m deficient mouse strain with low MHC Class I expression. Our data show that this mouse strain has an impaired reproductive performance. However, the mice superovulate well and show a normal estrous cycle. Breeding studies from crosses between the transgenic mice and the wild-type parental strain show that B2m deficient mice have a significantly lower frequency of mating than the control B2m+/+ mice. In addition, the litter size and weaning success of B2m deficient mice were lower than the control. Perinatal lethality of the B2m deficient offspring was also inflicted by cannibalism of the young pups by the B2m deficient female. The impaired breeding phenotype (IBP) can be reversed by reintroducing the B2m gene in F1 heterozygous B2m+/− animals; thus the presence of B2M confers a normal breeding pattern. The acquisition of an impaired breeding phenotype (IBP) as a result of the knockout of B2m directly implicates B2M in the reproductive cycle of mice and raises the possibility of an effect of B2M on the reproduction of other mammals.

Cell bio-imaging reveals co-expression of HLA-G and HLA-E in human preimplantation embryos.

The non-classical major histocompatibility complex (MHC) class Ib antigens, termed HLA-G and HLA-E, have been associated with fetal maternal tolerance. The role of HLA-G in the preimplantation embryo remains unclear although immunoprotection, adhesion and cell signalling mechanisms have been suggested. Unlike HLA-G, HLA-E protein expression has not been previously studied in preimplantation embryos. Embryos and model trophoblast cell lines JEG-3 and BeWo were labelled with the HLA-G- and HLA-E-specific monoclonal antibodies MEMG9 and MEME07. Flow cytometry, confocal microscopy and single particle fluorescence imaging techniques were employed to investigate the spatial and temporal expression of these receptors. Lipid raft analysis and adhesion assays were performed to investigate the role of these receptors in cell membrane domains and in promoting adhesion by cell-to-cell contact. HLA-E and HLA-G were co-localized in the trophectoderm of day 6 blastocysts. Analysis on trophoblast cell lines revealed that 37% of HLA-G and 41% of HLA-E receptors were co-localized as tetramers or higher order homodimer clusters. HLA-G receptors did not appear to play a role in either cell adhesion or immunoreceptor signalling via lipid raft platforms on the cell membrane. A possible role of HLA-G and HLA-E in implantation via immunoregulation or modulation of uterine maternal leukocytes is discussed.

Regulation of Major Histocompatibility Complex and TAP Gene Products in Preimplantation Mouse Stage Embryos

PROBLEM: To determine the ontogeny of major histocompatibility complex (MHC) expression and TAP products in mouse embryos.

Lectin receptors on the peri- and early post-implantation mouse embryo

SummaryMouse embryos at the blastocyst, blastocyst outgrowth, and primitive streak (day 7.5) stages of development were analysed for expression of lectin receptors using a panel of six FITC-conjugated lectins with affinities for five distinct saccharides (BSL, ConA, DBA, LTL, UEA and WGA). Blastocyst trophoblast expressed receptors for all the lectins but later tissues of the trophectoderm lineage lost receptors for distinct but overlapping subsets of the lectin panel. The inner cell mass (ICM) of the early blastocyst lacked receptors only for UEA. Differentiation of primary endoderm was accompanied by the aquisition of UEA receptors but subsequent differentiation into visceral and parietal endoderm involved the loss of receptors for both fucose binding lectins (UEA and LTL). Embryonic ectoderm in the day 7.5 egg cylinder retained receptors only for ConA and WGA. Thus, in general, differentiation during the peri- and early post-implantation period was associated with a differential loss of lectin receptors in all cell lineages of the mouse conceptus.