Search PubMed⌕ Search

Biomedical subjects

B A Croy

Publications and source records attributed to B A Croy.

At least 91 records · Page 5Linked to original sources
PubMed1991

Demonstration of YAC target cell lysis by murine granulated metrial gland cells.

Granulated metrial gland (GMG) cells are a consistently observed but poorly understood feature of the murine uterus during successful pregnancy. From morphological studies and antibody phenotyping it has been suggested that GMG cells may be members of the natural killer (NK) cell lineage. However, lysis of murine NK cell targets by GMG cells has not been observed although lysis of freshly dissociated trophoblast cells by GMG cells has been recorded using timelapse video. We failed to demonstrate significant interactions between migrating GMG cells, collected from explant cultures under previously reported cultures conditions, and YAC target cells. However, YAC cell lysis did occur if hrIL-2 was present throughout the periods of explant culture and lysis assay. Furthermore, lysis was enhanced if the pregnant females were treated with the interferon inducer poly I.C. 24 hr before metrial gland collection. GMG cells expressed perforin and serine protease mRNA. Consistent with the lysis experiments, expression of these genes was enhanced when the cells were incubated with hrIL-2. Our data provide further support for a relationship between GMG cells and NK cells, but do not establish a relationship of identity since hrIL-2, a growth factor sufficient for the culture of NK cells, cannot support growth or prolong survival of GMG cells.

Animals↗
PubMed1991

Characterization of cytokine production by the metrial gland and granulated metrial gland cells.

The metrial gland and its population of bone marrow-derived, large, granulated, lymphocyte-like cells, termed granulated metrial gland (GMG) cells, are consistent but poorly understood, decidua-associated features of pregnancy in the mouse and other species. Decidua, a complex maternal tissue, is thought to be a source of cytokines important for placental development. Thus, it is important to determine if lymphokine or cytokine production is among the activities of the metrial gland and GMG cells. Media conditioned by culture of either metrial gland explants or migrating GMG cells were evaluated for various cytokine activities. At least four activities were present: CSF-1, IL-1, a factor promoting proliferation of DA-1 cells that was not GM-CSF, IL-3 or erythropoietin and an activity cytotoxic to the CSF-1-dependent macrophage cell line 5/10.14. CSF-1 and IL-1 appeared to be products of the GMG cells. Cytokines not present at detectable levels included IL-2, IL-4, TNF-alpha and TGF-beta. Qualitatively, the cytokine profiles remained constant throughout days 8-16 of gestation. mRNA from migratory GMG cells was isolated and assayed for eleven cytokine mRNAs by polymerase chain reaction-based amplification of cDNA synthesized from mRNA. GMG cell RNA contained transcripts for LIF and CSF-1 but did not contain transcripts for GM-CSF, G-CSF, IL-2, IL-3, IL-4, IL-6, IL-7, IFN-gamma or TNF-alpha. TGF-beta transcripts were detected in occasional samples at very low levels. Since GMG cells are highly mobile cells that migrate throughout the placenta and into trophoblast-lined maternal blood spaces, their function in pregnancy may involve the delivery of very localized differentiation or growth regulatory signals to the developing fetal trophoblast and placenta.

Animals↗
PubMed1991

Assessment of expression of the receptor for colony-stimulating factor-1 (fms) in bovine trophoblast.

Bovine trophoblast was employed to assess the questions of whether the receptor for CSF-1 is expressed by noninvasive trophoblast and whether expression changes with differentiation within placentomes. Bovine placental poly(A) mRNA contained sequences cross-reactive with cDNA probes to c-fms and v-fms. Using a monoclonal antibody to v-fms, immunohistochemistry of postattachment bovine trophoblast showed expression of an fms-like protein between Day 29 and term. Expression occurred in both the intercotyledonary and cotyledonary trophoblast. Reactivity that was fms-like was also demonstrated on preattachment conceptuses flushed at Days 14 and 7 of gestation and on Day 7 embryos derived from in vitro oocyte maturation and fertilization. Unexpectedly, in the second half of pregnancy some cells, including binucleate cells, showed nuclear rather than cytoplasmic reactivity to the antibody. These data indicate expression of an fms-like protein in bovine placenta that does not correlate with properties of trophoblast cell invasiveness or major morphological differentiation. The data do support a universal role for this protein during mammalian placental development.

Animals↗
PubMed1991

Failure to detect platelet-activating factor using the splenectomized mouse bioassay.

The ability of purified preparations of platelet-activating factor (PAF), from three different suppliers, to induce thrombocytopaenia in mice after splenectomy and to activate mouse platelets in vitro was examined. Although the PAF preparations were potent activators of horse and cow platelets in vitro, injections of up to 1 microgram PAF failed to elicit thrombocytopaenia responses in either CD1 or Swiss Webster random-bred mice. However, when thrombin was injected into Swiss Webster mice, a dose-dependent decrease in the concentration of platelets was observed. Furthermore, isolated platelets from these strains and from 3 inbred lines (C3H/He, BALB/c, C57BL/6) of mice, were not aggregated by PAF in vitro but were sensitive to adenosine diphosphate and thrombin. No change in circulating platelet concentrations was observed over the initial 7 days of gestation in intact Swiss Webster and C57BL/6 or splenectomized C57BL/6 mice, suggesting either an absence of PAF production during early pregnancy in these strains or insensitivity of their platelets to PAF. These results suggest that many mouse strains are unsuitable for the bioassay of PAF.

Adenosine Diphosphate↗
PubMed1991

Experimental sialodacryoadenitis virus infection in severe combined immunodeficient mice.

Mice with a severe combined immunodeficiency in B and T lymphocytes and natural killer cells (SCID-beige) were inoculated intranasally with sialodacryoadenitis (SDA) virus, a coronavirus of rats. Animals were killed at designated intervals and tissues were examined for evidence of viral infection by light microscopy and immunofluorescence microscopy. Based on these criteria, there was no evidence that these immunodeficient mice were susceptible to infection with SDA virus.

Animals↗
PubMed1990

Demonstration of a splenic cytotoxic effector cell in mice of genotype SCID/SCID.BG/BG.

Splenocytes from mice of genotype scid/scid.bg/bg were tested in vitro to characterize the nature of the immunological deficit in these doubly mutant animals. The cells were unresponsive to the mitogens LPS and Con A and to alloantigens, as predicted for scid/scid genotype. Splenocytes from scid/scid.bg/bg lysed the NK cell-sensitive target cell line YAC at levels approximately 50% lower than those observed for scid/scid splenocytes. Splenocytes from SCID-beige mice failed to lyse the NK-resistant, LAK-sensitive cell line P815 but showed high levels of activity against the murine placental cell line Be6. Lytic activity was found in both nonadherent and plastic adherent cells and was eliminated by pretreatment of the effectors with anti-asialo-GM1 and complement. Incubation of 1 x 10(5) splenocytes with hrIL-2 failed to induce blastogenesis in scid/scid.bg/bg cells but produced a response in cultures of scid/scid or bg/bg spleen cells. However, blastogenesis and elevated levels of LAK-type killing were observed following incubation of higher numbers of scid/scid.bg/bg splenocytes in hrIL-2. Thus, doubly mutant scid/scid.bg/bg mice have reduced NK cell activity, in comparison to scid/scid mice, and appear to possess LAK-like effector cells and LAK cell precursors.

Animals↗
PubMed1990

Evaluation of the pregnancy immunotrophism hypothesis by assessment of the reproductive performance of young adult mice of genotype scid/scid.bg/bg.

The hypothesis that enhancement of pregnancy success results from immune recognition of the conceptus was evaluated by studying reproductive performance in a new line of mice deficient in NK cells and lacking B cells and T cells. Doubly mutant mice of genotype scid/scid.bg/bg are both viable and fertile. The numbers of offspring born to pairs of this genotype were not different from numbers born to heterozygous pairs. Differences in prenatal loss could not be found between genotypes by counts of either fetal resorption sites or corpora lutea. The timing of developmental stages and the differentiation of trophoblast, placenta, decidua and metrial gland in scid/scid.bg/bg mice appeared normal. These results suggest either that lymphokine influences on trophoblast cells in vivo do not contribute, in a major way, to pregnancy success or that the important cytokines are derived from uterine cell populations that are not classical, mature B cells, T cells or NK cells.

Animals↗
PubMed1989

Leucocyte membrane antigens on mouse granulated metrial gland cells.

An indirect immunofluorescence technique has been used to study the expression of leucocyte membrane antigens on mouse granulated metrial gland (GMG) cells. GMG cells isolated from cultured metrial gland explants and GMG cells in cryostat sections of uterine implantation sites were examined. GMG cells were found to express both the asialo-GM1 antigen and the Thy-1 antigen. GMG cells did not express the Lyt-1, Lyt-2, Mac-1, L3T4 or IgM antigens. These results provide new evidence that GMG cells are a type of NK cell.

Animals↗
PubMed1989

Evaluation of the murine metrial gland for immunological function.

The metrial gland (MG) is a transient uterine structure associated with rodent pregnancy. The gland is a complex structure consisting of stromal and vascular elements, as well as a population of histologically distinctive, large, granulated metrial gland (GMG) cells. The functions of the MG and of the GMG cells, as well as their relationship to the success of pregnancy, are unknown. Based upon morphological and morphometric studies it has been proposed that the MG might be involved in the immunology of pregnancy and that GMG cells could be immunocompetent. Explant cultures of MG have therefore been evaluated for immunological function. Lytic activity against the NK sensitive target cell line YAC and mitogen responsiveness could not be detected. MG tissue and medium conditioned by overnight culture of MG tissue (MG-CM) suppressed the response of murine spleen cells to Con A. MG-CM also reduced the lytic activity of splenic NK cells against YAC target cells. However, uptake of [3H]thymidine was elevated when YAC cells were cultured in MG-CM. The response of embryonic and uterine cells to growth in MG-CM was complex. MG-CM had little effect on isotope incorporation by decidual cells recovered at 6.5 days or by embryonic cells recovered from 12.5 day embryos. However, thymidine incorporation was less in MG-CM than in control medium for 12.5 day placental cells, 6.5 day embryonic sac, 6.5 day ectoplacental cone and 3.5 day blastocysts. Cytotoxicity and cytostasis accounted for reduced uptake of isotope in cultures of 3.5 day blastocysts and 6.5 day embryonic tissues. Loss of viability could not be detected in any other assays. Both YAC cells and unstimulated splenocytes showed altered morphology and improved viability when cultured in MG-CM. This study suggests that the only immunological role the MG might have during normal pregnancy is that of non-specific intra-uterine suppression. Alternatively, differential regulation of cell proliferation might be a function of the MG, within the pregnant uterus. The latter mechanism could also account for the apparent observation of non-specific immunosuppression.

Animals↗
PubMed1989

Morphological demonstration of the failure of Mus caroli trophoblast in the Mus musculus uterus.

A histological study of Mus caroli embryos gestating in the Mus musculus uterus was undertaken at Day 8.5 of gestation, 1 day after such embryos are reported to be normal and 1 day before the earliest events associated with death of the xenogeneic embryos. In comparison to control M. caroli embryos recovered from M. caroli and to control M. musculus embryos recovered from M. musculus, the xenogeneically transferred embryos showed intrauterine growth retardation that was associated with trophoblastic insufficiency. Trophoblast cell degeneration was observed, in the absence of lymphocytic infiltration. Therefore, loss of trophoblast cell function rather than lymphocyte-mediated destruction of trophoblast appears to underlie the death of M. caroli embryos in the M. musculus uterus.

Abortion, Spontaneous↗
PubMed1988

Normal murine and porcine embryos recruit NK cells to the uterus.

Decidual NK cells, indistinguishable from those found in lymphoid tissues, are present in cell suspensions prepared from maternal decidua of random-bred mice between Days 6.5 and 10.5 of first gestation. The stringency of the correlation between NK cells and normal embryos during successful pregnancy is unknown. Our previous finding that active NK cells were unable to mediate lysis of fresh embryonic tissues at any stage during gestation suggests that if NK cells play a functional role in normal pregnancy it would be a noncytolytic role. Before studies on the function of uterine NK cells were undertaken, evidence that the association of NK cells with normal embryos is widespread was sought by assessing NK cell activity in cell suspensions from decidua of syngeneically mated mice, from decidua of multiparous, random-bred mice, and from the endometrium of pigs during first pregnancy. Neither parity nor maternal-fetal compatibility changed the pattern of high levels of decidual NK cell activity early in pregnancy followed by decline. Porcine NK cell activity was not detected in uterine cells isolated from cycling pigs but in pregnant animals it gradually increased during the preattachment period and reached levels greater than those in blood, postattachment (Day 28). Some of this activity was hormone dependent but sustained increases in NK cell activity required the presence of an embryo. These studies demonstrate that the association of functional NK cells with normal embryos is widespread during early pregnancy.

Animals↗
PubMed1988

Assessment of immunoregulation by cultured, pre-attachment bovine embryos.

The possibility that the viability of bovine embryos might be predicted by measuring their release of immunoregulatory substances during culture has been investigated. Bovine embryos between days 2 and 19 of gestation were cultured for 24-48 h, the embryo-conditioned medium was harvested and studied for suppression of PHA-stimulated bovine leukocyte cultures. Medium incubated in the absence of any conditioning tissues served as control. Artefactual immunosuppression was detected in incubated control material that could be attributed, in part, to the mixing of different tissue culture media, the type of plastic-ware employed for incubation and supplementation of media with additional L-glutamine. It was observed that day-2 to day-9 bovine embryos, cultured in medium able to support the lymphocyte proliferation assay, did not release immunosuppressive substances. Medium conditioned by day-10 to day-12 embryos produced variable immunosuppression while that conditioned by trophoblastic vesicles derived from day-14 to day-19 embryos was consistently highly suppressive. Since bovine embryo transfer is normally conducted at 6-8 days of gestation, it is unlikely that measuring the immunosuppressive products released from bovine embryos will be of value for predicting their viability.

Animals↗
PubMed1988

Evidence that specific cellular immunity cannot account for death of Mus caroli embryos transferred to Mus musculus with severe combined immune deficiency disease.

Mus caroli blastocysts transferred to pseudopregnant Mus musculus implant but die about midgestation. Death of the M caroli embryos is associated with infiltration of the fetoplacental units by M musculus lymphocytes, including functional cytotoxic T lymphocytes (CTL). To determine if specific maternal antifetal immune responses are responsible for the initiation of M caroli failure, survival of M caroli embryos transferred to M musculus with severe combined immune deficiency disease (SCID) was studied. C.B.-17 scid mice, homozygous for the scid gene, are reported to be unresponsive to T cell or B cell mitogens and to alloantigens. We have evaluated responses of C.B.-17 scid mice to M caroli xenoantigens in vivo and in vitro. C.B.-17 scid fail to reject M caroli skin grafts, and their spleen cells do not proliferate when mixed with M caroli splenocytes in a 1-way mixed leukocyte culture. Further, neither primary nor secondary challenge of C.B.-17 scid footpads with M caroli splenocytes elicits a delayed-type hypersensitivity (DTH) response. These results suggest that C.B.-17 scid mice are unable to recognize or respond specifically to M caroli xenoantigens. M caroli embryos transferred to C.B.-17 scid mice implant but fail to survive while cotransferred M musculus embryos are normal. Histologic examination of resorbing embryos revealed granulocytes, macrophages, large granular lymphocytes, but very few small lymphocytes at the implantation sites. Thus, it appears that specific maternal antifetal immune responses are not responsible for initiation of M caroli embryo failure in the M musculus uterus. These studies also indicate that efficient resorption of embryos does not require the function of T cells or B cells.

Animals↗
PubMed1987

Evaluation of intrauterine immune suppression during pregnancy in a species with epitheliochorial placentation.

Cells capable of suppressing the immune response of PBL to the mitogen PHA are associated with the epitheliochorial placenta during normal first pregnancy in the pig. Because placentation in the pig is noninvasive, these suppressor cells are not associated with decidua. Cells with similar activity are also found between the implantation sites and in the uterus of pseudopregnant pigs, suggesting that fetal trophoblast is not essential for recruitment of intrauterine suppressor cells. Cell separation studies demonstrate that two independent populations of suppressor cells are present in the pig uterus on day 28 of gestation, as well as a population of PHA-responsive cells. The inability of unseparated porcine uterine cells to respond to PHA, plus the reconstitution of suppression in remixing experiments, demonstrate directly that a functional, putative T effector cell population is blocked within the uterus during normal mammalian pregnancy.

Animals↗