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Biomedical subjects

R Parkman

Publications and source records attributed to R Parkman.

At least 37 records · Page 2Linked to original sources
PubMed1995

The effect of thymic function on immunocompetence following bone marrow transplantation.

We investigated the role of thymic function in the immunodeficiency that characterizes bone marrow transplantation (BMT) recipients. The capacity of histocompatible BMT recipients to generate new CD4+ T lymphocytes was determined by FACS analysis with antibodies to the two isoforms of CD45: CD45RA, which is expressed on newly generated CD4 T lymphocytes, and CD45RO, which is expressed on antigen-specific memory CD4 T lymphocytes. Immediately following BMT, all patients had low levels of CD45RA-expressing CD4 T lymphocytes, which increased during the first year and then stabilized. Since thymic function decreases with age in normal individuals, the impact of recipient age on the generation of new CD45RA,CD4 T lymphocytes was determined in BMT recipients with and without chronic graft-vs.-host disease (GVHD). In addition, antigen-specific immune function was determined by assessing in vitro blastogenic response to tetanus toxoid (TT). More than 1 year after transplantation, the results from BMT recipients without chronic GVHD were similar to those of normal individuals; there was an age-dependent decline in the number of CD45RA,CD4 T lymphocytes, and antigen-specific immune function was age-independent. On the other hand, recipients with chronic GVHD had an age-dependent decline in their immune function (r = 0.45 and p = 0.02) that correlated with the number of new CD45RA,CD4 T lymphocytes (p = 0.027) but not the number of memory CD45RO,CD4 T lymphocytes (p = 0.11). Thus recipients with chronic GVHD have decreased antigen-specific immune function that may be due to an acceleration of the normal thymic aging process induced by GVHD and its therapy.

Bone Marrow Transplantation↗
PubMed1994

High levels of interleukin 10 production in vivo are associated with tolerance in SCID patients transplanted with HLA mismatched hematopoietic stem cells.

Transplantation of HLA mismatched hematopoietic stem cells in patients with severe combined immunodeficiency (SCID) can result in a selective engraftment of T cells of donor origin with complete immunologic reconstitution and in vivo tolerance. The latter may occur in the absence of clonal deletion of donor T lymphocytes able to recognize the host HLA antigens. The activity of these host-reactive T cells is suppressed in vivo, since no graft-vs. -host disease is observed in these human chimeras. Here it is shown that the CD4+ host-reactive T cell clones isolated from a SCID patient transplanted with fetal liver stem cells produce unusually high quantities of interleukin 10 (IL-10) and very low amounts of IL-2 after antigen-specific stimulation in vitro. The specific proliferative responses of the host-reactive T cell clones were considerably enhanced in the presence of neutralizing concentrations of an anti-IL-10 monoclonal antibody, suggesting that high levels of endogenous IL-10 suppress the activity of these cells. These in vitro data correlate with observations made in vivo. Semi-quantitative polymerase chain reaction analysis carried out on freshly isolated peripheral blood mononuclear cells (PBMC) of the patient indicated that the levels of IL-10 messenger RNA (mRNA) expression were strongly enhanced, whereas IL-2 mRNA expression was much lower than that in PBMC of healthy donors. In vivo IL-10 mRNA expression was not only high in the T cells, but also in the non-T cell fraction, indicating that host cells also contributed to the high levels of IL-10 in vivo. Patient-derived monocytes were found to be major IL-10 producers. Although no circulating IL-10 could be detected, freshly isolated monocytes of the patient showed a reduced expression of class II HLA antigens. However, their capacity to stimulate T cells of normal donors in primary mixed lymphocyte cultures was within the normal range. Interestingly, similar high in vivo IL-10 mRNA expressions in the T and non-T cell compartment were also observed in three SCID patients transplanted with fetal liver stem cells and in four SCID patients transplanted with T cell-depleted haploidentical bone marrow stem cells. Taken together, these data indicate that high endogenous IL-10 production is a general phenomenon in SCID patients in whom allogenic stem cell transplantation results in immunologic reconstitution and induction of tolerance. Both donor T cells and host accessory cells contribute to these high levels of IL-10, which would suppress the activity of host-reactive T cell in vivo.

Base Sequence↗
PubMed1994

Umbilical cord blood cell transduction by retroviral vectors: preclinical studies to optimize gene transfer.

Human umbilical cord blood (UCB) can be a source of hematopoietic stem cells for gene therapy, as an alternative to allogeneic bone marrow transplantation, for the treatment of a number of genetic diseases. To determine conditions that yield maximal gene transfer into UCB progenitor cells, we examined a number of variables. We used cell-free retroviral vector supernatants that convey neomycin (G418) resistance and measured the percentage of G418-resistant progenitor-derived colonies. Adding retroviral supernatant to the UCB cells in basal medium once a day for 3 days produced a threefold increase of G418-resistant colonies (9.8%) compared to a single exposure to supernatant (3.1%). To establish whether recombinant human growth factors are beneficial during transduction, the presence of interleukin-3 (IL-3), IL-6, and mast cell growth factor (MGF, a c-kit ligand) were compared in different combinations. Inclusion of the three factors together caused a threefold increase of gene transfer (30.4%) compared to transduction in basal medium. When the UCB cells were precultured in medium containing IL-3, IL-6, and MGF for 3 days before addition of the retroviral supernatant on days 4, 5, and 6, the average extent of gene transfer was 21.8%, compared with an average of 34.4% when UCB cells were transduced on days 1, 2, and 3. The presence of marrow stroma during the transduction of the UCB cells did not further increase gene transfer. We conclude that UCB progenitor cells can be efficiently transduced with the use of recombinant human growth factors IL-3, IL-6, and MGF and may be a suitable source for gene therapy.

Adenosine Deaminase↗
PubMed1993

Is chronic graft versus host disease an autoimmune disease?

Chronic graft versus host disease continues to be a major problem following bone marrow transplantation even though the incidence and severity of acute graft versus host disease has been reduced. Recent investigations have suggested that the pathogenesis of chronic graft versus host disease is more similar clinically to an autoimmune disease than to acute graft versus host disease.

Animals↗
PubMed1993

T lymphocyte ontogeny in adenosine deaminase-deficient severe combined immune deficiency after treatment with polyethylene glycol-modified adenosine deaminase.

Adenosine deaminase (ADA) deficiency causes severe combined immune deficiency (SCID) by interfering with the metabolism of deoxyadenosine, which is toxic to T lymphocytes at all stages of differentiation. Enzyme replacement with polyethylene glycol-modified ADA (PEG-ADA) has been previously shown to correct deoxyadenosine metabolism and improve mitogen-induced T lymphocyte proliferation. We studied the biochemical and immunologic effects of PEG-ADA in two infants with ADA-deficient SCID. While in a catabolic state, higher doses of PEG-ADA than previously described were required to normalize deoxyadenosine metabolism. After biochemical improvement, the patients recovered immune function in a pattern similar to that observed in normal thymic ontogeny and in patients with immunological reconstitution after bone marrow transplantation. Immune reconstitution was marked by the sequential appearance in the peripheral blood of phenotypic T lymphocytes corresponding to successive stages of thymic differentiation. Functional reconstitution was marked by the successive appearance of mitogen responses dependent on exogenous in vitro IL-2, mitogen responses not requiring exogenous IL-2, antigen-specific responses dependent on exogenous IL-2, and finally, antigen-specific responses not requiring exogenous IL-2. Natural killer function was tested in one patient and normalized with PEG-ADA therapy. Optimal PEG-ADA therapy appears to normalize thymic differentiation in ADA-deficient SCID, resulting in normal antigen-specific immune function.

Adenosine Deaminase↗
PubMed1993

Granulocyte recovery in pediatric marrow transplant recipients treated with ganciclovir for cytomegalovirus infection.

PURPOSE: Cytomegalovirus (CMV) infection remains a major cause of morbidity and mortality after bone marrow transplantation (BMT). Ganciclovir is a guanosine analogue that selectively inhibits CMV DNA polymerase and appears to be a useful agent for BMT patients with CMV pneumonia. One major side effect of ganciclovir is neutropenia, and there may be reluctance to administer ganciclovir to neutropenic patients. However, there is evidence that CMV infection may directly or indirectly cause marrow suppression. In this situation, the potential benefit of ganciclovir may outweigh the risk. PATIENTS AND METHODS: We retrospectively reviewed the charts of 11 consecutive patients receiving ganciclovir for CMV infection posttransplant. A total of 13 courses of ganciclovir were administered. RESULTS: In 10 of 13 cases, the absolute neutrophil count was higher at the completion of ganciclovir therapy than at the start of treatment, including five cases where the absolute neutrophil count was < 500/mm3 at the time ganciclovir was started. In only one of 13 cases was ganciclovir discontinued due to neutropenia. CONCLUSIONS: We conclude that the administration of ganciclovir is not often associated with the development of severe neutropenia in pediatric marrow transplant recipients and that ganciclovir can be safely administered to patients with CMV disease, who are severely neutropenic.

Adolescent↗
PubMed1993

Unrelated donor BMT for Wiskott-Aldrich syndrome.

The role of allogeneic sibling BMT for children with Wiskott-Aldrich syndrome is established. Mismatched T cell-depleted BMT has been successful, although significant problems with graft rejection, GVHD, and post-transplant lymphoproliferative disorders have been reported. We have performed four BMTs for children with Wiskott-Aldrich syndrome utilizing phenotypically HLA-identical unrelated donors. A non-TBI (total body irradiation) conditioning regimen was utilized, and BM was not T cell-depleted. All patients engrafted and developed significant, although manageable, GVHD. All patients are alive 3+ to 17+ months post-transplant. These results suggest that matched unrelated donor BMT has a definite role in the treatment of Wiskott-Aldrich syndrome.

Acute Disease↗
PubMed1992

Correction of antigen-specific T-lymphocyte function by recombinant cytokines in children infected with human immunodeficiency virus type 1.

To determine the role of cytokines in the immunodeficiency of children infected with human immunodeficiency virus type 1 (HIV-1), we compared the antigen-specific (tetanus toxoid-induced) T-lymphocyte blastogenesis of HIV-1-infected patients with and without the addition of exogenous interleukin-1 and interleukin-2. Acquisition of in vitro antigen-specific immunologic function was seen in some patients after the addition of exogenous cytokines. The antigen-specific immunodeficiency in some HIV-1-infected children is due to defects in cytokine production rather than to an absence of antigen-specific T lymphocytes.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Altered O-glycan synthesis in lymphocytes from patients with Wiskott-Aldrich syndrome.

The only molecular defect reported for the X-linked immunodeficiency Wiskott-Aldrich syndrome (WAS) is the abnormal electrophoretic behavior of the major T lymphocyte sialoglycoprotein CD43. Since the 70 to 80 O-linked carbohydrate chains of CD43 are known to influence markedly its electrophoretic mobility, we analyzed the structure and the biosynthesis of O-glycans of CD43 in lymphocytes from patients with WAS. Immunofluorescence analysis with the carbohydrate dependent anti-CD43 antibody T305 revealed that in 10 out of the 12 WAS patients tested increased numbers of T lymphocytes carry on CD43 an epitope which on normal lymphocytes is expressed only after activation. Other activation antigens were absent from WAS lymphocytes. Western blots of WAS cell lysates displayed a high molecular mass form of CD43 which reacted with the T305 antibody and which could be found on in vivo activated lymphocytes but was absent from normal unstimulated lymphocytes. To examine the O-glycan structures, carbohydrate labeled CD43 was immunoprecipitated and the released oligosaccharides identified. WAS lymphocyte CD43 was found to carry predominantly the branched structure NeuNAc alpha 2----3Gal beta 1----3 (NeuNAc alpha 2----3Gal beta 1----4G1cNAc beta 1----6) GalNAcOH whereas normal lymphocytes carry the structure NeuNAc alpha 2----3Gal beta 1----3 (NeuNAc alpha 2----6) GalNAcOH. Only after activation NeuNAc alpha 2----3Gal beta 1----3 (NeuNAc alpha 2----3Gal beta 1----4GlcNAc beta 1----6) GalNAcOH becomes the principal oligosaccharide on CD43 from normal lymphocytes. Analyzing the six glycosyltransferases involved in the biosynthesis of these O-glycan structures it was found that in WAS lymphocytes high levels of beta 1----6 N-acetyl-glucosaminyl transferase are responsible for the expression of NeuNAc alpha 2----3Gal beta 1----3 (NeuNAc alpha 2----3Gal beta 1----4GlcNAc beta 1----6) GalNAcOH on CD43. The gene responsible for WAS has not yet been identified but the results presented in this study suggest that the primary defect in WAS may affect a gene which is involved in the regulation of O-glycosylation.

Antigens, CD↗
PubMed1991

Severe combined immunodeficiency disease, adenosine deaminase deficiency and gene therapy.

Patients with severe combined immunodeficiency disease represent a model for the first clinical applications of gene therapy. Present attempts use insertion of the human adenosine deaminase gene into the peripheral blood T lymphocytes of patients who lack this gene. The ultimate treatment, however, will require insertion of the normal human adenosine deaminase gene into pluripotent stem cells and expression of the gene in their progeny.

Adenosine Deaminase↗