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T G Wegmann

Publications and source records attributed to T G Wegmann.

At least 55 records · Page 3Linked to original sources
PubMed1987

Facilitation of syngeneic stem cell engraftment by anti-class I monoclonal antibody pretreatment of unirradiated recipients.

We have established a murine model of syngeneic bone marrow transplantation based on the use of monoclonal antibody as the sole conditioning regimen in unirradiated recipients. Administration of a single injection of monoclonal antibody directed against major histocompatibility complex-encoded class I determinants facilitated permanent hemopoietic stem cell engraftment without any apparent side-effects. Whereas untreated hosts exhibited a maximal chimerism of 15% at donor cell doses of up to 12 X 10(7) bone marrow cells, pretreatment by 2 mg of anti-class I antibody one week prior to transplantation of 3 X 10(7) syngeneic bone marrow cells resulted in a mean donor representation of about 80%. The antibody can be given up to four weeks prior to transplantation, and the degree of donor engraftment observed is a function of the dose of antibody administered. The fact that specific antibody enhanced engraftment in two strain combinations indicates that antibody is the active agent in facilitating engraftment and that facilitation is not strain-restricted. Anti-class I antibodies of the IgG2a, but not IgG1, isotype are effective in promoting engraftment. Although the isotype requirement suggests a role for antibody-mediated cytotoxicity in promoting stem cell engraftment, the extensive time-frame of facilitation suggests that other effects of the antibody may also be involved. The model of syngeneic bone marrow transplantation we describe here will be useful in studying the mechanisms regulating stem cell engraftment and may have potential clinical application as an approach to autologous marrow transplantation.

Animals↗
PubMed1986

Placental immunoregulation.

Mammalian gestation is complex and varies widely among species, but the embryonic contribution to the maternal-fetal interface, the trophoblast, remains constant. Alloantigen and stage/tissue specific antigens are present on the trophoblast in low concentration and often in locations inaccessible to maternal immune effectors. Nonetheless, pregnancy does prime the mother for humoral immunity; cell-mediated responses are more difficult to demonstrate. The placenta appears to be an efficient block to cellular traffic into the fetus; the placental barrier to specific antibody has been established, but its efficiency is controversial. Nonspecific, local, active suppression mediated by lymphoid cells within the decidua is apparently an important concomitant of successful gestation. Yet there is evidence that an ongoing immune response is beneficial to pregnancy, allowing an increase in placental size in response to growth-promoting lymphokines while blocking graft-rejection mechanisms. Thus it appears that immunoregulation at the maternal-fetal interface is complex, and no single mechanism can account for the success of the "fetal allograft".

Animals↗
PubMed1985

The human alpha-fetoprotein gene. Sequence organization and the 5' flanking region.

The human alpha-fetoprotein (AFP) gene was isolated into three overlapping clones in bacteriophage lambda vectors and its sequence organization analyzed by restriction endonuclease mapping and nucleotide sequencing. The human AFP gene is about 20 kilobase pairs long and contains 15 exons and 14 introns. The overall organization of the human AFP gene is similar to that of the mouse AFP gene, with all but two exons showing identical sizes. Nucleotide sequences at all exon/intron junctions display similarity to the consensus boundary sequence (Breathnach, R., and Chambon, P. (1981) Annu. Rev. Biochem. 50, 349-383), with the GT-AG rule applied to the splicing point. The cap site maps 44 nucleotides upstream from the translation initiation site. The "TATA box" is located 27 nucleotides upstream from the putative cap site and is flanked by sequences with dyad symmetry. The TATA box can thus be placed in the loop portion of a possible stem-loop structure formed by intrastrand base-pairing. Other characteristic nucleotide sequences in the 5' flanking region include a CCAAC pentamer, a 14-base pair (bp) enhancer-like sequence, and a 9-bp sequence homologous to the glucocorticoid responsive element. A long (90 bp) direct repeat and several alternating purine/pyrimidine sequences are also present in the 5' flanking region. A 736-bp sequence of the 5' flanking region adjacent to the cap site of the human AFP gene shows a 61% similarity with the corresponding region of the mouse AFP gene. There are two Alu family sequences and two poly(dT-dG) repeats in the human AFP gene that show different distribution patterns from those in the mouse AFP gene.

Amino Acid Sequence↗
PubMed1985

Characterization of immune effector cells present in early murine decidua.

It has been suggested that murine decidual cells act as an important immunoregulatory population localized to the pregnant uterus. We have examined early murine decidua to determine if immune effector cells occur in the decidual environment in proximity to the conceptus. High levels of natural killer (NK) cell activity were found consistently in decidual cell suspensions with peak activity occurring on Day 6.5 of gestation. NK activity declined as pregnancy proceeded and was not significant by Day 12.5 of gestation. Decidual cell suspensions did not appear to contain significant numbers of functional B or T effector cells. No antipaternal T-cell response could be demonstrated even in the decidua of immune mice. Lack of T-cell responses was attributed to the absence of T cells from decidua rather than to their inactivation because precursors of cytotoxic T lymphocytes (pCTL) could not be detected in decidual cell suspensions. Furthermore, the levels of pCTL detectable in spleen cell suspensions could not be reduced by mixing spleen cells with 7.5-day decidual cells. These results suggest that B cells and T cells may not occur in early decidua while NK cells are present and regulated independently.

Animals↗
PubMed1985

Characterization of murine decidual natural killer (NK) cells and their relevance to the success of pregnancy.

The identification of lytic cells in 6.5-day to 9.5-day murine decidua as NK cells has been extended. The cells with natural killer (NK) activity in early decidua were nonphagocytic and heterogeneous in size as assessed by velocity sedimentation at unit gravity. The numbers of lytic cells were reduced by treatment with anti-asialo GM1 in vivo and they were absent from the decidua of bg/bg mice. Thus, decidual NK cells were not distinct from NK cells in other tissues. The decline in the levels of decidual NK activity as pregnancy progressed was attributed to their regulation by other cells present in decidua by midgestation. The development of NK activity in decidua was dependent upon the presence of an embryo, however, decidual NK cells were not essential for successful pregnancy because viable offspring were obtained from mice lacking decidual NK activity. It was shown that NK cells from either spleen or decidua were unlikely to cause damage to embryos during the first half of pregnancy as freshly dissociated 9.5- and 11.5-day embryonic cells resisted NK lysis. Furthermore, blastocysts were not damaged by coincubation with splenic or decidual NK cells and were viable upon subsequent embryo transfer. These studies indicate that decidual NK cells are not essential for successful pregnancy and are not necessarily detrimental to early embryos. It is suggested that decidual NK cells may play other nonimmunological roles during embryonic development.

Animals↗
PubMed1985

Isolation of cDNA clones encoding a T-cell receptor beta-chain from a beef insulin-specific hybridoma.

cDNA clones coding for a T-cell receptor beta-chain were isolated from a beef insulin/IAd-reactive T-cell hybridoma, A20.2.15, and its complete amino acid sequence was deduced. This beta-chain gene utilizes the same V beta segment as a thymocyte beta-chain gene (86T1) and rearranges to the 5' proximal J-C locus (J beta 1-C beta 1), thus providing definitive evidence of a beta-chain gene from a functional hybridoma that utilizes C beta 1. The amino acid sequence of the V beta gene in A20.2.15 is identical to 86T1, thus suggesting the absence of somatic mutation in the beta-chain of A20.2.15. Southern blot analysis revealed a somatic DNA rearrangement unique to the A20.2.15 hybridoma. The expression of this gene in the hybridoma was confirmed by RNA dot hybridization. All 24 beta-chain clones so far isolated from the A20.2.15 hybridoma contained C beta 1, suggesting that the beta-chain gene of the fusion partner BW5147 is not expressed in the hybridoma.

Amino Acid Sequence↗
PubMed1985

Characterization of hemopoietic stem cell chimerism in antibody-facilitated bone marrow chimeras.

We have previously described a model for bone marrow transplantation that involves preparation of the host with monoclonal antibody against class I or class II antigens instead of irradiation or cytotoxic drugs. This allows engraftment and subsequent repopulation of the host by donor tissue. We have previously reported on chimerism in the peripheral blood of P1----(P1 X P2)F1 animals. In this report, we describe the examination of the bone marrow and spleen stem cell chimerism of these antibody-facilitated (AF) chimeras, by determining, with an isozyme assay, the phenotype of methylcellulose colonies grown from stem cells. We have found a correlation between peripheral blood chimerism and the stem cell constitution of both spleen and bone marrow. The peripheral blood chimerism also correlates with the level of chimerism in macrophages derived from peritoneal exudate cells. These findings indicate that assaying the peripheral blood of such chimeras provides an excellent indication of the degree of chimerism at the stem cell level and stands in sharp contrast to the level of chimerism in certain lymphoid compartments, as described in our accompanying article.

Animals↗
PubMed1985

Characterization of host lymphoid cells in antibody-facilitated bone marrow chimeras.

We have produced stable murine antibody-facilitated (AF) chimeras by the simultaneous injection of P1 bone marrow cells and anti-P2 monoclonal antibody into normal (unirradiated) adult (P1 X P2)F1 recipients. These AF chimeras are healthy, long-lived, and exhibit no overt signs of graft-versus-host disease. They are immunocompetent and tolerant of host, P2-encoded alloantigens. Donor cell engraftment and takeover, monitored by glucosephosphate isomerase isozyme patterns, is usually complete (greater than 95%) in the peripheral blood, bone marrow, and hemopoietic stem cell compartments of long-term (greater than 3 months posttransplantation) AF chimeras. We report here, however, that splenic, lymph node, and thymic leukocytes of AF chimeras represent donor/host chimeric populations. Spleen cell populations of AF chimeras exhibit substantial chimera-to-chimera variation in the preponderant residual host cell type(s) present. Our interpretations of the implications of these findings are discussed.

Animals↗
PubMed1985

Immunologic consequences of vaccination against abortion in mice.

CBA/J female mice have a high rate of fetal resorption when mated with DBA/2J males. This fetal wastage can be dramatically reduced by immunizing the female with BALB/cJ but not DBA/2J spleen cells. We report here that immunization with BALB/cJ (but not DBA/2J) spleen cells leads to 1) anti-paternal MHC antibody that is predominantly of the IgG1 isotype, and which disappears from the serum during pregnancy; 2) increased active suppression in both the spleen and placenta; and 3) an ability to adoptively transfer the fetal protection and placental suppression with serum from the immunized mice. Congenic absorption studies before adoptive transfer indicate that the active component of the serum is also directed against the paternal MHC haplotype. These results indicate that maternal humoral immunity can lead to increased fetal protection in correlation with local active suppression in the placenta. They also suggest an expansion of the placental immunoabsorbent hypothesis to include the induction of active suppression against maternal cell-mediated immunity.

Animals↗
PubMed1985

Immunogenetic studies of spontaneous abortion in mice. Preimmunization of females with allogeneic cells.

CBA females (H-2k) mated with DBA2 males (H-2d) exhibit a high rate of fetal resorption (30%) when compared with the CBA female BALB/c male, CBA female/CBA male, DBA2 female/CBA male, DBA2 female/DBA2 male combinations (6 to 8%). Preimmunization of CBA females with spleen cells from DBA2, BALB/c, or CBA males were performed in order to test their effects on CBA maternal tolerance of (CBA X DBA2)F1 fetuses. Only preimmunization with BALB/c male cells was effective in decreasing resorption; cells from BALB/c females had no effect. In order to further test 1) the role of non-MHC-encoded antigens present in the BALB/c male background, 2) the necessity of an additional H-2 difference, and 3) whether or not the phenomenon is H-2d restricted, preimmunizations were performed by using cells from congenic BALB/k (H-2k), BALB/b (H-2b), or BALB/c (H-2d). Only the latter treatment was efficient, which suggests that the paternal H-2d haplotype must be presented in synergy with some non-MHC-encoded antigens in the BALB/c male background. Immunogenetic studies with cells from nine recombinant inbred strains that reassorted DBA2 and BALB/c genomes showed that three of them behave like BALB/c and six like DBA2. This would suggest that the genetic determinism of this phenomenon is simple.

Abortion, Spontaneous↗
PubMed1984

Antigen-specific helper T cells recognize determinants encoded in the H-2D region of the H-2 gene complex.

Observations have frequently been interpreted as showing that the helper T cells which collaborate with alloantigen-specific cytotoxic T-cell precursors can only recognize antigens encoded in the I region of the H-2 gene complex. An experimental system is described here that allows analysis of the recognition repertoire of these helper cells. CBA helper T-cell precursors can be primed in vitro to antigens encoded in the H-2b gene complex. These helpers can then be tested for the existence of a subset of helper cells which recognize antigens encoded in the D region of H-2b haplotype. CBA thymocytes were used as a source of cytotoxic T-cell precursors that respond poorly in the absence of exogeneous helper activity. The source of alloantigen was varied by using irradiated spleen cells from various (BALB/c X recombinant)F1 hybrid mice as stimulator cells. When the stimulator cell bears BALB/c determinants recognized by the cytotoxic T-cell precursor and also bears only the D region antigens of the H-2b haplotype, an anti-BALB/c cytotoxic response is generated only if the anti-H-2b helper population contains cells able to recognize H-2Db. A positive cytotoxic response was obtained, indicating that helper cells are not limited to recognition of I region antigens and can efficiently recognize antigens encoded in the D region of the H-2 gene complex. This was confirmed by the demonstration of helpers specific for H-2Dd. We were unable to detect any evidence for Ia-restricted recognition of the H-2D alloantigens, suggesting that, as for cytotoxic T lymphocytes (CTL), helper cell recognition of class I alloantigens is an unrestricted event.

Animals↗
PubMed1984

Fate of antipaternal H-2 antibodies bound to the placenta in vivo.

We have previously demonstrated that the placental spongiotrophoblast and yolk sac venous plexus express paternally derived H-2K and D (class I) antigens in a manner accessible to maternal circulation, and that the placenta serves to prevent antipaternal antibodies from reaching the fetus. Kinetic studies indicated that the placenta is capable of reexpressing its H-2 antigens after having been bound by anti-H-2 antibodies, suggesting that the placental cells somehow have the ability to eliminate the bound antibodies. In order to investigate the fate of the antibodies, we have followed the uptake and fate of radiolabeled anti-H-2Kk monoclonal antibody in the placentas of target allogeneic and control syngeneic pregnancies. Chromatographic analyses indicate that most of the intercellular radiolabel is associated with fragments smaller than IgG, and similar degradation was not observed with syngeneic control placentas. We conclude that the placenta is capable of binding, ingesting, and then digesting antipaternal H-2 antibodies, further substantiating the immunoabsorbent barrier hypothesis of allogeneic fetal survival.

Animals↗
PubMed1984

Antibody-facilitated chimeras. Stem cell allotransplantation using antihost major histocompatibility complex monoclonal antibodies instead of lethal irradiation for host conditioning.

Complete hemopoietic takeover between semiallogeneic adults can be accomplished by the administration of antihost major histocompatibility complex (MHC) monoclonal antibody (mAb) and donor stem cells. The recipients of such treatment are termed antibody-facilitated chimeras, and they have been produced in (BALB/cCr----(BALB/cCr X C3H/HeJ)F1 and DBA/2J----(DBA/2J X C3H/HeJ)F1 strain combinations. Donor stem cells can be derived from spleen, bone marrow, or T-cell-depleted bone marrow. Engraftment by donor hemopoietic cells can be facilitated by mAbs directed toward class I (anti-H-2Kk) or class II (anti-H-2I-Ak) MHC antigens of the host. By monitoring isozymes of glucose phosphate isomerase, it can be shown that the establishment of donor hemopoiesis is stable, persisting for more than a year without graft-versus-host disease. The effect of anti-MHC mAb on pluripotential stem cells was evaluated by the (colony-forming units-spleen) (CFU-S) assay. The number of CFU-S in target (H-2k) bone marrow was reduced by in vitro pretreatment with anti-H-2Kk mAb, but not with anti-H-2I-Ak mAb. In contrast, in vivo administration of either anti-H-2Kk or anti-H-2I-Ak mAb resulted in a marked decrease in the CFU-S capacity of relevant strain mice. These observations suggest that the target of the in vivo mAb treatment may be pluripotential stem cells--or perhaps the hemopoietic microenvironment.

Animals↗
PubMed1984

Placenta as a selective barrier to cellular traffic.

Transplacental passage of cells from mother to fetus during murine pregnancy was examined by using glucose phosphate isomerase (GPI) or fluorescein tagging as markers. Female mice of strains (BALB/cCr X C3H/HeJ)/F1 or (A/J X C57BL/6J)F1 (both Gpi-1a/b) were mated to the corresponding Gpi-la males (BALB/cCr or A/J, respectively). Cells of the liver, blood, and/or spleen in the offspring were typed at days 15, 16, 17, or 18 of gestation, the day of delivery, or 1 day postpartum. Only two of 172 Gpi-1a/a mice obtained from these matings showed evidence of maternal cell trafficking. Sensitivity of the assay was 1% Gpi-1a/a population. Fluorescein-labeled BALB/cCr peripheral red blood cells (RBC) or white blood cells (WBC) were injected i.v. into syngeneically mated BALB/cCr mothers on day 18. After 24 hr, the blood or liver of the neonates was formalin-fixed and examined in the fluorescence-activated cell sorter (FACS). Some RBC crossed the placenta, but WBC were usually not detected in fetal liver in significant numbers. This technique was very sensitive, and we estimated that no more than 225 WBC could enter the fetus via this route. Thus, we conclude that passage of significant numbers of maternal WBC into the fetus is rare, and perhaps this passage is related to a placental abnormality.

Animals↗