Search PubMed⌕ Search

Biomedical subjects

F H Bach

Publications and source records attributed to F H Bach.

At least 145 records · Page 8Linked to original sources
PubMed1993

A multigene family on human chromosome 12 encodes natural killer-cell lectins.

We previously isolated a series of cDNA clones designated NKG2-A, B, C, and D from a human natural killer (NK) cell library. These transcripts encode a family of type II integral membrane proteins having an extracellular Ca(2+)-dependent lectin domain. The predicted peptides share structural similarities and amino acid sequence similarity with known receptor molecules. In this report, the genomic organization and mRNA expression of each of the genes were studied by using transcript-specific probes. Southern blot experiments reveal that the probes cross-hybridize with a maximum of five genes at high stringency. By probing a Southern blot prepared from a series of hamster/human hybrid somatic cell lines, we demonstrated that all of the hybridizing fragments occur on human chromosome 12. No gene rearrangement and little restriction fragment length polymorphism (RFLP) was observed with these probes. mRNA expression of the NKG2 genes occurred in NK cells and some T cells but not in other hematopoietic cell types or in other tissues tested. Each of the transcripts occurred in all three of the NK cell lines tested: however, the genes were differentially regulated in T cells. NKG2-D was expressed in nine of fourteen T-cell clones or lines in the panel, whereas NKG2-A/B was expressed in three and NKG2-C was expressed in only one. Expression of each of the transcripts was upregulated following T-cell growth factor (TCGF)-induced activation of a cloned NK cell. The limited distribution of these proteins and their sequence similarity with known receptor molecules suggest that they may function as receptors on human NK cells.

Alternative Splicing↗
PubMed1993

Characterization of a novel gene (NKG7) on human chromosome 19 that is expressed in natural killer cells and T cells.

NKG7 is a cDNA clone generated from a human NK-cell clone. The DNA and predicted aa sequence of NKG7 is not homologous with any previously reported genes or peptides. NKG7 mRNA is expressed in activated T cells and in A-LAK cells isolated from the peripheral blood of normal individuals, and in normal human kidney, liver, lung and pancreas. Furthermore, NKG7 mRNA is expressed at high levels in TCR gamma delta-expressing CTL clones, and in some TCR alpha beta-expressing CTL clones (both CD4+ and CD8+), but is not expressed in other TCR alpha beta-expressing CTL clones and in cell lines representing B cells, monocytes, and myeloid cells. NKG7 mRNA is not expressed in normal human brain, heart, or skeletal muscle. Southern hybridization of NKG7 suggests that NKG7 is a single-copy gene localized to chromosome 19. A hydropathicity profile of the predicted 148 aa polypeptide indicates that NKG7 is a type-I integral membrane protein with a 38-aa extracellular domain and a 61-aa cytoplasmic domain. These results indicate that the NKG7 gene encodes a novel cell surface protein expressed in several cell types, including NK cells and T cells.

Amino Acid Sequence↗
PubMed1993

Evidence that polyreactive antibodies are deposited in rejected discordant xenografts.

The rejection of organs transplanted between phylogenetically disparate species is thought to be initiated by the binding of naturally occurring antibodies of the recipient to the endothelium lining the blood vessels of the donor organ. We recently showed that among the xenoreactive natural antibodies in human serum that react with porcine endothelial cells and endothelial cell--derived glycoproteins are polyreactive antibodies. To test whether polyreactive natural antibodies are present in rejected xenografts we developed a series of hybridoma-derived antibodies specific for the polyreactive human monoclonal antibody 103, which we have shown to bind efficiently to porcine endothelial cells. Using these antiidiotypic reagents we detected antibodies bearing the 103 idiotype in a panel of human sera and on the surface of lymphocytes in the spleen of humans, rhesus monkeys, and baboons. The antiidiotypic reagents reacted in a pattern similar to the distribution of IgM, with immunoglobulin deposits in tissues obtained from pig-to-rhesus monkey and pig-to-baboon xenografts. Analysis of immunoglobulin eluted from these sites showed that they antibodies display the antigen-binding features of natural antibodies. Our findings are consistent with the hypothesis that idiotypes of polyreactive natural antibodies are broadly crossreactive. They also suggest that the polyreactive and xenoreactive IgM, which have been detected based on in vitro assays, may be deposited in a xenogeneic organ graft.

Animals↗
PubMed1993

Suppression of synthesis of natural antibodies by mycophenolate mofetil (RS-61443). Its potential use in discordant xenografting.

One of the major barriers to successful transplantation of immediately vascularized organs between discordant species is the presence of natural antibodies (NA) in the recipient. While natural antibodies can be depleted by plasmapheresis and/or organ absorption, they rapidly return to the circulation after such procedures. It will be desirable to suppress NA for longer periods of time. Since NA appear to be produced at least in part by CD5+ B cells, it was important to evaluate whether mycophenolate mofetil (RS-61443), a novel immunosuppressant that has been shown to suppress normally elicited antibody synthesis, would also be able to suppress NA. Adult rats were splenectomized, and 2 days later, 9 plasma exchanges, each of 4 ml, were performed. One group of rats received RS-61443 at 40 mg/kg/day (the dose described as efficacious for suppressing elicited antibodies in rats) starting immediately after the last exchange for 7 days, and then 20 mg/kg/day for an additional 7 days; no drug was given to the control group. NA levels were measured at various times by ELISA, using guinea pig platelets extracts as the target. Splenectomy alone led to a significant decrease from the control levels of NA; titers were further reduced by the plasma exchanges. In the absence of RS-61443, NA titers rose steadily, starting at 24 hr after the last plasma exchange. In contrast, administration of RS-61443 resulted in levels of NA on day 7 not significantly different from those after plasma exchange, reducing the dose of RS-61443 to the 20 mg/kg/day level during week 2 allowed the gradual return of NA. Administration of RS-61443 at the 40 mg/kg/day dose to rats after splenectomy alone led to a clear and significant further decrease in NA levels over the first week. It has been shown that RS-61443 can be administered for longer periods. The data presented suggest that use of this drug, perhaps with more conventional agents, may allow suppression of NA for a significant period after transplantation.

Animals↗
PubMed1993

In vivo depletion of xenoreactive natural antibodies with an anti-mu monoclonal antibody.

Hyperacute rejection of vascularized discordant xenografts, such as pig-to-primate kidney or heart xenotransplants, is thought to be mediated by xenoreactive natural antibodies (XNA) of the IgM isotype and the activation of the classic pathway of complement. Using the guinea pig-to-rat discordant xenograft model, we have developed a potential therapeutic protocol leading to long-term depletion of circulating IgM in adult animals. This protocol consists of the injection into adult LOU/C rats of an antirat IgM MAb (MARM-7) after splenectomy, plasma exchange, and the administration of an anti-B cell immunosuppressant, mycophenylate mofetil (RS61443). Splectomized plasma exchanged adult rats receiving RS61443 showed strongly decreased IgG and IgM serum concentrations for a relatively short period during which these isotypes remained nevertheless detectable by a sensitive ELISA technique. In contrast to IgM, IgG in serum returned, shortly after the end of this treatment, to normal concentrations. Splenectomy alone was able to significantly decrease, for a long period (more than 70 days), IgM but not IgG serum concentrations in these rats. During this treatment, IgM XNA concentration mirrored total IgM. The injection of MARM-7 MAb to adult LOU/C rats was able to deplete circulating IgM and IgM XNA for a period of several weeks during which IgM was undetectable by a sensitive ELISA technique. Depletion time was dose-dependent--the higher the dose of injected MARM-7, the longer the period for which IgM and IgM XNA remained undetectable. Moreover depletion of circulating IgM was correlated with the detection in the serum of these rats of noncomplexed, free MARM-7. Finally, MARM-7 administration was significantly more efficacious in rats that had decreased levels of circulating IgM after splenectomy, plasma exchange, and administration of RS61443. These experiments suggest that the anti-mu approach may allow depletion of IgM XNA for a sufficiently long period to test the hypothesis of "accommodation" in other xenograft models such as the pig-to-primate xenograft or even in ABO-incompatible allografts.

Animals↗
PubMed1993

Molecular analysis of the immune response to human cytomegalovirus glycoprotein B. I. Mapping of HLA-restricted helper T cell epitopes on gp93.

Human cytomegalovirus (HCMV) is one of the most common causes of congenital infection leading to birth defects, and a leading cause of serious illness in patients with impaired cell-mediated immunity. Helper T cell (Th) responses to HCMV proteins are likely to be important in limiting viral replication and preventing disease. Previous studies from this laboratory have demonstrated that the amino-terminal 513 amino acids of HCMV glycoprotein B (gB) can stimulate both B and T cell responses in humans. In the present study, the proliferative responses of HCMV-specific Th clones to recombinant proteins and synthetic peptides were examined to identify four Th epitopes on gp93, which represents the amino-terminal 460 amino acids of the gB polypeptide. Using clones of known HLA restriction specificity from several donors, it was shown that each HLA class II allele preferentially associates with a different epitope on gB. Five clones from two different donors recognized an epitope in the region of amino acids 250 to 264 restricted by DR4Dw14, two clones from different donors recognized an epitope in the region of amino acids 420 to 434 restricted by DR7Dw17, two clones from different donors recognized an epitope in the region of amino acids 178 to 194 restricted by DQw1 and a single clone recognized an epitope in the region of amino acids 190 to 204 restricted by DPw4. Although all peripheral blood mononuclear cells (PBMCs) expressing a particular HLA class II allele were able to present the appropriate HLA-restricted gB peptide to gB-specific Th clones, not all individuals expressing a given HLA allele exhibited PBMC responses to the corresponding gB peptide. The HLA-related differences in Th recognition of specific epitopes on gB described in this report may have important implications in virus-host interactions and vaccine strategies.

Adult↗
PubMed1993

Murine APC activation in the xenogeneic MLC.

Purified human T cells proliferate in response to direct and indirect presentation of human alloantigens. However, until recently it was believed that human T cells could respond only indirectly to murine xenoantigens. We recently used the mixed leucocyte culture (MLC) to demonstrate that purified human T cells proliferate in response to direct presentation of murine xenoantigens by murine antigen-presenting cells (APC) in the presence of human cytokines. We suggested that cytokines might function poorly across species barriers. In this study, we demonstrate that although proliferation occurs in the presence of exogenously added cytokines, the precursor frequency of responding human T cells is much lower in a xenogeneic than in an allogeneic MLC. We demonstrate that human T cells also proliferate in response to murine APC in the presence of murine cytokines, and murine cytokines augment the proliferative response seen in a human anti-human MLC, ruling out the possibility that an absolute cytokine incompatibility exists between these species. We show that exogenously added human IL-1 causes maximal proliferation of human T cells in response to murine xenoantigens only when added early in the culture. We further demonstrate that murine APC preincubated in human rIL-1, and washed extensively, prior to use as stimulating cells, cause human T-cell proliferation without the need for exogenously added cytokines. Finally, we noted that during interactions of human T cells and murine APC, little to no IL-1 is produced, whereas after the addition of exogenous IL-1, a marked increase in the production of IL-1 is seen. These data suggest that during interactions between human T cells and murine APC, the murine cells do not receive adequate stimulation to produce sufficient costimulatory signals to allow proliferation of the human T cells.

Animals↗
PubMed1992

Administration of a prostaglandin synthetase inhibitor associated with an increased immune cell infiltrate in squamous cell carcinoma of the head and neck.

Squamous cell carcinoma of the head and neck produces a prostaglandin, PGE2, a potent inhibitor of cellular immune responses. We tested the effects of prostaglandin synthetase inhibition on the infiltration of squamous cell carcinoma of the head and neck with host lymphocytes. Tumor tissue samples were obtained from six patients (age range, 51 to 72 years) who presented with squamous cell carcinoma of the head and neck before and after 14 days of treatment with indomethacin (50 mg administered orally three times a day). Tumor-infiltrating immune cells were assayed in frozen tissue samples by indirect immunofluorescence. An eightfold increase in CD2+ lymphocytes compared with pretreatment tissue was observed. The number of CD4 and CD8 lymphocytes increased similarly. CD57 lymphocytes increased 15-fold and CD11b cells increased 11-fold. No infiltrating B-cell populations were evident. Double-labeling studies revealed that the mononuclear cells were located outside blood vessel walls, indicating that they had infiltrated the tumor parenchyma. Our findings demonstrate that the administration of indomethacin is associated with the increased immune cell infiltration of squamous cell carcinoma of the head and neck. This suggests that inhibition of PGE2 synthesis as it occurs in the tumor and or systemically may contribute to the homing of mononuclear cells to the tumor. These data suggest a mechanism to account for the clinical response to indomethacin previously reported in squamous cell carcinoma.

Aged↗
PubMed1992

Relationship of large and small CD3- CD56+ lymphocytes mediating NK-associated activities.

We have defined a population of CD3-, CD56+ small lymphocytes (SLs) that exhibit the same phenotype and lytic capacity as natural killer (NK) cells. NK cells characteristically express the surface markers CD16 and CD56, mediate non-major histocompatibility complex (MHC)-restricted lysis, and have been equated with CD3- large granular lymphocytes (LGLs). In the present study we extended the observation that CD3-, CD56+ SLs can mediate NK- and antibody-dependent cellular cytotoxicity activity by studying the activation signals and lytic mechanisms that might be utilized by CD3-, CD56+ SLs in comparison to CD3- CD56+ LGLs. Our results show that CD3- SLs, similar to CD3- LGLs, exhibited activated killing in response to interleukin-2 (IL-2). In addition, after IL-2 activation, the CD3- SLs exhibited morphologic changes, including increases in size and granularity, and both morphologically and phenotypically became virtually indistinguishable from CD3- LGLs. Similar to CD3- LGLs, CD3- SLs could be directly activated by IL-2 alone to secrete significant quantities of interferon-gamma (IFN-gamma) and to express IL-2 receptor (IL-2R) p55. Examination of serine esterases and pore-forming protein (PFP) demonstrated that these cells exhibited a cytoplasmic distribution of perforin, which, unlike that of CD3- LGLs, was not associated with dense cytoplasmic azurophilic granules. Serine esterase levels were similar. However, after IL-2 activation PFP was concentrated in dense cytoplasmic granules, similar or identical to the situation in CD3-, CD56+ LGLs. These CD3-, CD56+ subsets appear to represent a continuum of activated cells that might represent various states of maturation of NK cells.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1992

Candidate natural killer cell receptors.

Among the high points of immunological discovery has been the identification of antigen-recognizing receptors on B and T cells. Of the lymphocyte populations, only the NK cell receptor remains unknown. Consequently, any newly-recognized, cell-surface molecules expressed selectively on NK cells, especially ones that can transmit a signal to the cell upon appropriate ligand interaction, are possible candidates. This article describes such candidates.

Animals↗
PubMed1992

Cell subsets responding to purified hepatocytes and evidence of indirect recognition of hepatocyte major histocompatibility complex class I antigen. I. The role of L3T4+ T cells in the development of allospecific cytotoxicity in hepatocyte-sponge matrix allografts.

The purpose of this study was to determine the role of L3T4+, Ly2- T cells in the development of allospecific cytolytic T cells in response to purified allogeneic MHC class I+, class II- hepatocytes in vivo in hepatocyte-sponge matrix allografts (HC-SMA). In previous studies we have shown that 99% pure murine hepatocytes stimulate the development of allospecific cytolytic T cells in vitro in mixed lymphocyte-hepatocyte culture (MLHC) and in vivo in HC-SMA. Furthermore, depletion of L3T4+, Ly2- T cells from responder splenocytes inhibits the development of allo-CTLs in response to purified hepatocytes in mixed lymphocyte-hepatocyte culture. Here, using an anti-L3T4 monoclonal antibody, we tested the effect of in vivo immunodepletion of L3T4+, Ly2- T cells on the subsequent development of allo-CTLs in HC-SMA. Sponge cells were harvested on day 4 and day 12 after grafting from control and treated groups and phenotypically analyzed by FACS and immunofluorescent labelling. Splenocytes from the same animals were similarly analyzed to assess for completeness of immunodepletion. Allospecific cytotoxicity was assessed on day 12 after grafting. We found that immunotherapy with anti-L3T4 mAb was effective in depleting L3T4+, Ly2- T cells from the spleen; however, a similar number of L3T4+ cells was isolated from the sponge between control and treated groups. Furthermore, the development of allo-CTLs in response to hepatocytes in HC-SMA was completely abrogated by both local and systemic immunotherapy with anti-L3T4 mAb. We conclude from these and previous data that host or responder L3T4+, Ly2- T cells and responder accessory cells in MLHC or host macrophages in HC-SMA may participate in "indirect" recognition of hepatocyte class I antigen both in vitro and in vivo.

Animals↗
PubMed1992

Cell subsets responding to purified hepatocytes and evidence of indirect recognition of hepatocyte major histocompatibility complex class I antigen. II. In vitro-generated "memory" cells to class I+ class II- hepatocytes.

Purified hepatocytes stimulate the development of L3T4-, Ly2+ allospecific cytolytic T cells from naive splenocytes after 5 days in primary mixed lymphocyte-hepatocyte culture (MLHC). Previous studies indicate that the immunogenicity of purified hepatocytes relates to the expression of MHC class I antigen. The purpose of the following experiments was to identify the cell subsets that specifically recognize hepatocyte MHC class I antigen. We employed primed lymphocyte testing (PLT) in order to test for a "second set" response. Cells from primary MLHC reverted to a functionally quiescent state when they were grown in culture for an additional 7-9 days. The cells were then tested for cytotoxicity or rechallenged with allogeneic, syngeneic, or "third party" hepatocytes and tested for proliferation. Allocytotoxicity was low on day 12 in MLHC, but the sensitized cell population demonstrated peak proliferation in response to allogeneic hepatocytes 48 hr after restimulation. When bulk PLT cells were immunodepleted, both L3T4+, Ly2- and L3T4-, Ly2+ T cell subsets demonstrated a "second set" response to allogeneic hepatocytes consistent with specific recognition of and retention of "memory" for hepatocyte MHC class I alloantigen.

Animals↗
PubMed1992

Evidence that 15-deoxyspergualin inhibits natural antibody production but fails to prevent hyperacute rejection in a discordant xenograft model.

Preventing hyperacute rejection (HAR) is a difficult and unsolved problem in xenotransplantation. This may be due, in part, to a lack of therapies that can suppress production of natural antibodies (NA), which are thought to be critical mediators of HAR. This study examined the effect of 15-deoxyspergualin (DSPG) and splenectomy (Spx) on NA production and return of NA after plasma exchange (PE) in a discordant species combination (strain 2 guinea pig to Lewis rat). A dose of 5 mg/kg/day DSPG + Spx significantly reduced Lewis rat anti-guinea pig NA titer after one week of therapy. Antibody titer was not significantly reduced in rats treated with splenectomy alone. PE alone acutely depleted NA titers; however, complete rebound was seen in 48 hr. When PE was performed in rats treated with DSPG + Spx, an additional significant NA reduction occurred; no rebound 24-48 hr after PE was seen. Except for a 20% reduction in body weight, no serious complications occurred in DSPG + Spx recipients. Despite a profound NA titer reduction, treatment with DSPG, Spx, and PE did not prolong guinea pig cardiac xenograft survival in a clinically significant fashion. Immunopathological study of rejected cardiac xenografts revealed no antibody deposition but persistent complement deposition on vascular endothelium. We conclude that DSPG + Spx effectively inhibits synthesis of rat anti-guinea pig NA, that further NA titer reduction can be achieved with the addition of PE, and that DSPG + Spx prevents post-PE antibody rebound. We also conclude that the limited prolongation in cardiac xenograft survival achieved, despite marked suppression of NA, supports a complement-mediated mechanism of HAR in our animal model.

Animals↗