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Biomedical subjects

John Iacomini

Publications and source records attributed to John Iacomini.

At least 19 recordsLinked to original sources
PubMed2006

Induction of alloreactive CD4 T cell tolerance in molecular chimeras: a possible role for regulatory T cells.

Induction of molecular chimerism following reconstitution of mice with autologous bone marrow cells expressing a retrovirally encoded allogeneic MHC class I Ag results in donor-specific tolerance. To investigate the mechanism by which CD4 T cells that recognize allogeneic MHC class I through the indirect pathway of Ag presentation are rendered tolerant in molecular chimeras, transgenic mice expressing a TCR on CD4 T cells specific for peptides derived from K(b) were used. CD4 T cells expressing the transgenic TCR were detected in mice reconstituted with bone marrow cells transduced with retroviruses carrying the gene encoding H-2K(b), albeit detection was at lower levels than in mice receiving mock-transduced bone marrow. Despite the presence of CD4 T cells expressing an alloreactive TCR, mice receiving H-2K(b)-transduced bone marrow permanently accepted K(b) disparate skin grafts. CD4+CD25+ T cells from mice reconstituted with H-2K(b)-transduced bone marrow prevented rejection of K(b) disparate skin grafts when adoptively transferred into immunodeficient mice along with effector T cells, suggesting that induction of molecular chimerism leads to the generation of donor specific regulatory T cells, which may be involved in preventing alloreactive CD4 T cell responses that lead to rejection.

Animals↗
PubMed2005

Oocyte generation in adult mammalian ovaries by putative germ cells in bone marrow and peripheral blood.

It has been suggested that germline stem cells maintain oogenesis in postnatal mouse ovaries. Here we show that adult mouse ovaries rapidly generate hundreds of oocytes, despite a small premeiotic germ cell pool. In considering the possibility of an extragonadal source of germ cells, we show expression of germline markers in bone marrow (BM). Further, BM transplantation restores oocyte production in wild-type mice sterilized by chemotherapy, as well as in ataxia telangiectasia-mutated gene-deficient mice, which are otherwise incapable of making oocytes. Donor-derived oocytes are also observed in female mice following peripheral blood transplantation. Although the fertilizability and developmental competency of the BM and peripheral blood-derived oocytes remain to be established, their morphology, enclosure within follicles, and expression of germ-cell- and oocyte-specific markers collectively support that these cells are bona fide oocytes. These results identify BM as a potential source of germ cells that could sustain oocyte production in adulthood.

Adult↗
PubMed2005

The influence of natural antibody specificity on antigen immunogenicity.

The natural antibody repertoire in humans, apes and Old World primates is distinct from the repertoire of all other placental mammals, and encodes antibodies specific for the carbohydrate epitope Galalpha1-3Galbeta1-4GlcNAc-R (alphaGal). Here, we examined whether conjugating antigens to the alphaGal epitope can augment their immunogenicity in alpha(1,3)galactosyltransferase knockout mice (GT0 mice) which, like humans, produce alphaGal-specific antibodies. Immunization of GT0 mice with BSA conjugated to alphaGal (alphaGal-BSA) led to significant production of anti-BSA IgG antibodies without the need for adjuvant. This response was dependent on the presence of alphaGal-reactive antibodies. Immunization of wild-type mice with alphaGal-BSA failed to induce an anti-BSA response. The presence of alphaGal-reactive antibodies also led to an increase in the T cell response to BSA following immunization with alphaGal-BSA when compared with mice that received BSA alone, resulting in an increased frequency of IFN-gamma- and IL-4-producing BSA-specific T cells. In addition, the ability to produce alphaGal-reactive antibodies enhanced the cytotoxic T lymphocyte anti-viral antigen response following vaccination with murine leukemia virus transformed cell lines that express alphaGal on their cell surface. Natural antibodies that bind alphaGal therefore play a key role in increasing the efficiency of priming to antigens decorated with alphaGal epitopes.

Animals↗
PubMed2005

Induction of donor-specific tolerance in sublethally irradiated recipients by gene therapy.

Donor-specific transplantation tolerance can be established through the induction of molecular chimerism following reconstitution of lethally irradiated mice with autologous bone marrow expressing retrovirally transduced allogeneic MHC antigens. Here, we set out to define nonmyeloablative host conditioning regimens that would allow for establishment of molecular chimerism and the induction of donor-specific tolerance. Recipient mice received various doses of whole-body irradiation, together with costimulatory blockade using anti-CD154 monoclonal antibody prior to reconstitution with syngeneic bone marrow cells transduced with retroviruses carrying the gene encoding H-2K(b). Conditioning consisting of 3 Gy whole-body irradiation and treatment with anti-CD154 was sufficient to induce molecular chimerism resulting in stable multilineage expression of K(b) on hematopoietic cells. T cells from molecular chimeras were unable to lyse allogeneic targets expressing K(b) and contained substantially fewer K(b)-reactive IL-2- and IFN-gamma-producing CD4 T cells than controls receiving mock-transduced bone marrow. Induction of molecular chimerism using nonmyeloablative host conditioning allowed for permanent survival of K(b)-disparate allogeneic skin grafts. These data suggest that nonmyeloablative host conditioning can be used effectively to induce molecular chimerism resulting in transplantation tolerance.

Animals↗
PubMed2004

Induction of central tolerance by mature T cells.

Induction of immunological tolerance is highly desirable for the treatment and prevention of autoimmunity, allergy, and organ transplant rejection. Adoptive transfer of MHC class I disparate mature T cells at the time of reconstitution of mice with syngeneic bone marrow resulted in specific tolerance to allogeneic skin grafts that were matched to the T cell donor strain. Mature allogeneic T cells survived long-term in reconstituted hosts and were able to re-enter the thymus. Analysis of T cell development using transgenic mice expressing an alloantigen-reactive TCR revealed that expression of allogeneic MHC class I on adoptively transferred mature T cells mediated negative selection of developing alloreactive T cells in the thymus. Thus, mature allogeneic T cells are able to mediate central deletion of alloreactive cells and induce transplantation tolerance without the requirement for any other alloantigen-expressing cell type.

Adoptive Transfer↗
PubMed2004

Bone marrow transplantation restores immune system function and prevents lymphoma in Atm-deficient mice.

Ataxia-telangiectasia (A-T) is a human autosomal recessive disease caused by mutations in the gene encoding ataxia-telangiectasia mutated (ATM). A-T is characterized by progressive cerebellar degeneration, variable immunodeficiency, and a high incidence of leukemia and lymphoma. Recurrent sino-pulmonary infections secondary to immunodeficiency and hematopoietic malignancies are major causes of morbidity and mortality in A-T patients. In mice, an introduced mutation in Atm leads to a phenotype that recapitulates many of the symptoms of A-T, including immune system abnormalities and susceptibility to malignancy. Here we show that the replacement of the bone marrow compartment in Atm knockout mice (Atm(-/-)) using a clinically relevant, nonmyeloablative host-conditioning regimen can be used to overcome the immune deficiencies and prevent the malignancies observed in these mice. Therefore, bone marrow transplantation may prove to be of therapeutic benefit in A-T patients.

Animals↗
PubMed2004

The role of complement receptors in production of antibodies specific for Galalpha1,3Gal.

By using alpha-galactosyl transferase knockout (GT-/-) mice, which make natural alphaGal-reactive antibodies, we examined the role of complement receptors in the production of alphaGal-specific antibodies. GT-/- mice were crossed with complement receptor 2 loci knockout mice to generate double knockout (DKO) mice. alphaGal-specific natural antibodies were detectable by enzyme-linked immunosorbent assay in the serum of GT-/- mice by 9 weeks of age. In contrast, only low titers of alphaGal-specific natural antibodies were detectable only in the serum of older DKO mice. Serum titers of alphaGal-reactive antibodies in GT-/- mice increased significantly after immunization with pig cells. In contrast, immunization had little effect on alphaGal-reactive antibody levels in DKO mice. Similarly, pretreatment of GT-/- mice with a blocking antibody to CD21 and CD35 inhibited production of alphaGal-reactive antibodies after immunization. However, DKO mice were able to make alphaGal-specific antibodies after secondary immunization. Thus, Cr2 loci-encoded receptors seem to be directly involved in the production of primary alphaGal-reactive antibodies.

Animals↗
PubMed2004

Prevention of type 1 diabetes by gene therapy.

The autoimmune disease type 1 diabetes in humans and NOD mice is determined by multiple genetic factors, among the strongest of which is the inheritance of diabetes-permissive MHC class II alleles associated with susceptibility to disease. Here we examined whether expression of MHC class II alleles associated with resistance to disease could be used to prevent the occurrence of diabetes. Expression of diabetes-resistant MHC class II I-Abeta chain molecules in NOD mice following retroviral transduction of autologous bone marrow hematopoietic stem cells prevented the development of autoreactive T cells by intrathymic deletion and protected the mice from the development of insulitis and diabetes. These data suggest that type 1 diabetes could be prevented in individuals expressing MHC alleles associated with susceptibility to disease by restoration of protective MHC class II expression through genetic engineering of hematopoietic stem cells.

Animals↗
PubMed2003

Induction of T cell tolerance to a protein expressed in the cytoplasm through retroviral-mediated gene transfer.

BACKGROUND: Host immune responses to foreign gene products have been shown to lead to the elimination of genetically modified cells, and are a major barrier to successful therapeutic gene therapy. We have shown that immunological tolerance to retrovirally transduced cell surface proteins can be induced by expressing the gene encoding these products in bone marrow derived cells. Here, we investigate if expression of foreign gene products in bone marrow derived cells can be used to induce tolerance to cytoplasmic proteins. METHODS: Balb/c mice were reconstituted with syngeneic bone marrow cells transduced with retrovirus carrying the gene encoding enhanced green fluorescent protein (eGFP), or mock-transduced bone marrow cells. After reconstitution, mice were immunized with cells expressing eGFP, and T cells were tested for the ability to kill eGFP-expressing targets in in vitro cytotoxic T lymphocyte (CTL) assays. RESULTS: T cells from Balb/c mice reconstituted with mock-transduced bone marrow were able to kill target cells expressing eGFP. In contrast, T cells from mice reconstituted with eGFP-transduced bone marrow were unable to kill targets expressing eGFP. In addition, we observed that T cell responses to eGFP in C57BL/6 mice were minimal even under highly immunogenic conditions. CONCLUSIONS: These data suggest that expression of foreign gene products in bone marrow derived cells is capable of inducing T cell tolerance to proteins expressed exclusively in the cytoplasm.

Animals↗
PubMed2002

T cells mediate resistance to genetically modified bone marrow in lethally irradiated recipients.

BACKGROUND: In order for gene therapy to attain clinical relevance, efficient engraftment and long-term survival of cells that express transduced genes of interest must be achieved. In this study, we examined the extent to which host T cells affect engraftment of syngeneic bone marrow cells engineered to express a retrovirally transduced allogeneic major histocompatibility complex class-I gene. METHODS: B10.AKM mice were preconditioned with lethal irradiation or lethal irradiation plus transient CD4 and CD8 T-cell depletion in addition to CD40-CD154 costimulatory blockade and were then reconstituted with syngeneic bone marrow cells transduced with retroviruses that carried the gene that encoded H-2K(b) (K(b)). Expression of K(b) on bone marrow-derived cells was then analyzed, and induction of tolerance to K was evaluated. RESULTS: Mice conditioned using CD4 and CD8 T-cell depletion in addition to CD40-CD154 costimulatory blockade and lethal irradiation showed a significant increase in the frequency of bone marrow-derived cells that expressed K(b) when compared to animals that received lethal irradiation alone. Survival of allogeneic skin grafts that expressed K(b) was significantly prolonged in animals conditioned with anti-CD4, anti-CD8, and co-stimulatory blockade in addition to lethal irradiation (median survival time, 81 days) when compared to mice that received irradiation alone (mean survival time, 31 days; P=0.001). CONCLUSIONS: Radioresistant host T cells significantly affect the ability to induce tolerance by gene therapy by affecting engraftment of transduced cells that expressed allogeneic major histocompatibility complex class-I genes in the absence of host T-cell depletion and costimulatory blockade, even after lethal irradiation. Thus, radioresistant host T cells are a significant barrier to engraftment of transduced bone marrow progenitors and to the induction of tolerance by gene therapy.

Animals↗
PubMed2002

Expression of antigen on mature lymphocytes is required to induce T cell tolerance by gene therapy.

Expression of a retrovirally encoded allogeneic MHC class I gene in bone marrow-derived cells can be used to induce tolerance to the product of the retrovirally transduced gene. In this work we examined whether expression of a retrovirally transduced allogeneic MHC class I gene in bone marrow-derived cells from recombinase-activating gene-1 (RAG-1)-deficient mice was sufficient to induce tolerance when transplanted into conditioned hosts together with bone marrow from MHC-matched wild-type mice. Reconstitution of mice with either MHC-matched RAG-1-deficient or wild-type bone marrow transduced with the allogeneic MHC class I gene H-2K(b) led to long-term expression of K(b) on the surface of bone marrow-derived hematopoietic lineages. T cells from mice reconstituted with H-2K(b)-transduced wild-type bone marrow were tolerant to K(b). In contrast, expression of K(b) in the periphery of mice reconstituted with a mixture of retrovirally transduced RAG-1-deficient bone marrow and mock-transduced wild-type bone marrow fell below detectable levels by 4 wk after transplantation. T cells that developed in these mice appeared to be hyporesponsive to K(b), demonstrating that expression of K(b) on bone marrow-derived APCs was not sufficient to induce tolerance. Our data suggest that induction of tolerance in molecular chimeras requires expression of the retrovirally transduced allogeneic MHC Ag on the surface of mature lymphocytes that populate the host thymus.

Animals↗
PubMed2002

Induction of central deletional T cell tolerance by gene therapy.

Transgenic mice expressing an alloreactive TCR specific for the MHC class I Ag K(b) were used to examine the mechanism by which genetic engineering of bone marrow induces T cell tolerance. Reconstitution of lethally irradiated mice with bone marrow infected with retroviruses carrying the MHC class I gene H-2K(b) resulted in lifelong expression of K(b) on bone marrow-derived cells. While CD8 T cells expressing the transgenic TCR developed in control mice reconstituted with mock-transduced bone marrow, CD8 T cells expressing the transgenic TCR failed to develop in mice reconstituted with H-2K(b) transduced bone marrow. Analysis of transgene-expressing CD8 T cells in the thymus and periphery of reconstituted mice revealed that CD8 T cells expressing the transgenic TCR underwent negative selection in the thymus of mice reconstituted with K(b) transduced bone marrow. Negative selection induced by gene therapy resulted in tolerance to K(b). Thus, genetic engineering of bone marrow can be used to alter T cell education in the thymus by inducing negative selection.

Animals↗
PubMed2002

Induction of T-cell tolerance to an MHC class I alloantigen by gene therapy.

Induction of immunologic tolerance to alloantigens is a major goal in the field of transplantation. Here, we demonstrate that efficient transduction and expression of a retrovirally transduced major histocompatibility complex (MHC) class I gene (H-2K(b)) in bone marrow (BM)-derived cells, resulting in a permanent state of hematopoietic molecular chimerism, induces stable tolerance to the transduced gene product. Reconstitution of lethally irradiated syngeneic recipients with BM transduced with virus encoding H-2K(b) resulted in life-long expression of the retroviral gene product on the surface of BM-derived hematopoietic lineages including Sca-1(+), lineage negative, hematopoietic progenitors. T cells from mice receiving MHC-transduced BM were unable to kill targets expressing H-2K(b) but were able to respond to third-party controls. Mice reconstituted with H-2K(b)-transduced BM exhibited long-term acceptance of H-2K(b) mismatched skin grafts but were able to rapidly reject third-party control grafts. Thus, gene therapy approaches may be used to induce T-cell tolerance.

Animals↗
PubMed2002

Immunoglobulin heavy chain transgenic mice expressing Galalpha(1,3)Gal-reactive antibodies.

BACKGROUND: Natural antibodies that bind the carbohydrate antigen Galalpha1-3Galbeta1-4GlcNAc-R (alphaGal) mediate rigorous rejection of porcine xenografts and represent a major immunological hurdle to successful discordant xenotransplantation. However, little is known about how production of antibodies specific for alphaGal is regulated. METHODS: Transgenic mice expressing an IgM heavy chain isolated from a B-cell hybridoma that produces antibodies specific for alphaGal were constructed. These mice were bred to mutant mice that lack the alphaGal epitope (GT0 mice) or wild-type (GT+) mice to generate animals in which the transgene is expressed in the presence or absence of alphaGal as a "self"-antigen. Development of transgene-expressing B cells and production of alphaGal-specific serum antibodies were then analyzed in transgenic mice on GT0 and GT+ backgrounds. RESULTS: B cells expressing the transgenic heavy chain and transgene-encoded serum antibodies specific for alphaGal were readily detected in mice on the GT0 background. Most alphaGal-reactive antibodies in GT0 mice used the transgene rather than endogenous Ig heavy chains. In contrast, transgene-encoded serum antibodies specific for alphaGal were not detected in GT+ mice. In transgenic mice on the GT+ background, B cells expressing the transgene underwent deletion as a result of encountering alphaGal during their development, indicating that expression of alphaGal as part of self-mediated efficient negative selection of B cells expressing transgene-encoded alphaGal-specific antibodies. CONCLUSIONS: The development of transgenic mice expressing a B cell receptor specific for alphaGal provides a novel system to study developmental regulation of B cells making carbohydrate-specific antibodies. In addition, these mice may be useful for examining methods to prevent production of alphaGal-reactive antibodies.

Animals↗
PubMed2002

Establishing immunological tolerance through the induction of molecular chimerism.

One of the major goals of transplantation biology is to overcome transplant rejection without the need for life-long immunosuppression. Over the last several years, fundamental advances in our understanding of the immune response to allogeneic and xenogeneic antigens have stimulated a great deal of interest in the possibility of using gene therapy approaches to overcome the host response leading to transplant rejection while alleviating the need for non-specific immunosuppression. Here, we review recent progress in the field on the use of gene therapy to induce transplantation tolerance to donor organs and tissues.

Animals↗