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Biomedical subjects

T N Small

Publications and source records attributed to T N Small.

At least 37 records · Page 2Linked to original sources
PubMed1997

Immune reconstitution following T-cell depleted bone marrow transplantation: effect of age and posttransplant graft rejection prophylaxis.

Transplantation of T-cell depleted bone marrow has been associated with an increased risk of graft failure, requiring additional immunosuppression to prevent this complication. To determine the effect of graft rejection prophylaxis with posttransplant anti-thymocyte globulin and methylprednisolone on immune reconstitution, the lymphoid phenotype, function, and infectious complications of 170 recipients of a T-cell depleted bone marrow transplantation, 57 of whom received prophylaxis, were analyzed. Neutrophil recovery and normalization of T-cell numbers were more rapid in patients given anti-thymocyte globulin and methylprednisolone. Adults given graft rejection prophylaxis had prolonged inversion of their CD4/CD8 ratio, increased numbers of CD8+ CD11b+, HLA-DR+, CD57+, CD28- T cells, and delayed recovery of T-cell mitogen responses when compared to adults not given ATG and steroids. Even without posttransplant immunosuppression to prevent graft failure, adults experienced delayed recovery of total and CD45RA+ CD4+ cells, prolonged inversion of the CD4/CD8 ratio, and delayed recovery of T-cell mitogen responses when compared to children. During the first posttransplant year, Epstein-Barr Virus-Associated Lymphoproliferative disorders and opportunistic infections were increased in patients given prophylaxis. Patients who developed an opportunistic infection or EBV-LPD had significantly fewer circulating CD4+ T cells than those who did not. This study demonstrates that older age and graft rejection prophylaxis, rather than T-cell depletion alone, are associated with delayed immune reconstitution. In addition, it suggests that CD4 cell counts may be useful in predicting which patients are at increased risk of developing opportunistic infections following successful engraftment.

Adolescent↗
PubMed1996

The development of cellular immunity to Epstein-Barr virus after allogeneic bone marrow transplantation.

Epstein-Barr virus-induced lymphoproliferative disease (EBV-LPD) is a potentially lethal complication during the first 6 months after allogeneic bone marrow transplantation (BMT). To determine whether deficiencies of EBV-specific cellular immunity contribute to EBV-LPD susceptibility and distinguish patients at risk, we performed limiting dilution analysis to quantify anti-EBV cytotoxic T-lymphocyte precursor (CTLp) frequencies in 26 recipients of unmodified or T-cell-depleted (TCD) grafts from EBV-seropositive donors. At 3 months post-BMT (n = 26), only five patients had EBV CTLp frequencies in the range of seropositive normal controls, irrespective of the type of transplant administered. By 6 months post-BMT, 9 of 13 patients tested had EBV CTLp frequencies within the normal range. The time period in which these patients had deficient cellular immunity to EBV corresponds to the period in which we have observed EBV-LPD in most prior patients. One patient with a low EBV CTLp frequency at 4 months post-BMT developed an EBV-LPD. Within 2 weeks of receiving an infusion of donor peripheral blood mononuclear cells (PBMC) providing less than 1,200 EBV-specific cytotoxic T-cell precursors, populations of EBV-specific CTL in the circulation were restored to levels detected in normal seropositive adults. Concurrently, the patient achieved a regression of the EBV-LPD, which has been sustained without further therapy. These studies indicate that recipients of both unmodified and TCD marrow grafts have profound deficiencies of EBV-specific T cell-mediated immunity early posttransplant, and that the period of risk for EBV-LPD closely corresponds to this interval of severe deficiency. Treatment of one patient with EBV-LPD with marrow donor-derived PBMC induced a rapid expansion of EBV-specific cytotoxic T-cell populations that occurred contemporaneously with the clinical regression of disease.

Adolescent↗
PubMed1996

Immunologic reconstitution following stem cell transplantation.

The efficacy of bone marrow transplantation is contingent on not only the eradication of malignancy and restoration of hematopoiesis, but also successful reconstitution of the immune system. Opportunistic infections, despite resolution of neutropenia, continue to be the major cause of nonrelapse mortality following HLA-matched sibling transplants and are often the main cause of overall mortality following unrelated marrow transplantation. In two unrelated transplant series published within the past year fatal viral, fungal, and/or parasitic infections accounted for 16% and 34% of the mortality observed in children and adults, respectively, following unrelated bone marrow transplantation. Unfortunately, mortality secondary to infection has not changed significantly following unrelated bone marrow transplantation over the past 5 years. T- and B-cell deficits after transplantation have been well recognized. During the past year, not only have additional defects been elucidated, but two successful strategies to overcome them, namely adoptive immunotherapy to restore cytomegalovirus and Epstein-Barr virus cellular immunity, have been reported.

Adult↗
PubMed1995

Mycobacterium haemophilum infections in bone marrow transplant recipients.

The purpose of this study was to describe the clinical presentation, treatment, and outcome of Mycobacterium haemophilum infection in patients undergoing bone marrow transplantation at a cancer center. Bone marrow transplant recipients with M haemophilum infection were identified upon culture of the organism by implementing the organism's unique requirements for growth. This report of the patients' clinical and immunologic course is based on a retrospective chart review. Two distinctly different presentations of M haemophilum infection were observed. Three patients presented with cutaneous lesions, typical of those seen in previous reports of the infection. Two others developed pulmonary disease only. All patients received directed therapy against M haemophilum, but respiratory failure developed in the patients with pneumonia and they died. The remaining 3 patients survived and are free of infection. These are the only reported cases of M haemophilum infection in bone marrow transplant recipients. Early diagnosis obtained through biopsy and special request for culture conditions conducive to the growth of the organism may decrease morbidity and mortality, particularly in patients with pulmonary disease.

Adult↗
PubMed1995

Two mutational hotspots in the interleukin-2 receptor gamma chain gene causing human X-linked severe combined immunodeficiency.

Human severe combined immunodeficiency (SCID), a syndrome of profoundly impaired cellular and humoral immunity, is most commonly caused by mutations in the X-linked gene for interleukin-2 (IL-2) receptor gamma chain (IL2RG). For mutational analysis of IL2RG in males with SCID, SSCP screening was followed by DNA sequencing. Of 40 IL2RG mutations found in unrelated SCID patients, 6 were point mutations at the CpG dinucleotide at cDNA 690-691, encoding amino acid R226. This residue lies in the extracellular domain of the protein in a region not previously recognized to be significantly conserved in the cytokine receptor gene family, 11 amino acids upstream from the highly conserved WSXWS motif. Three additional instances of mutation at another CpG dinucleotide at cDNA 879 produced a premature termination signal in the intracellular domain of IL2RG, resulting in loss of the SH2-homologous intracellular domain known to be essential for signaling from the IL-2 receptor complex. Mutations at these two hotspots constitute > 20% of the X-linked SCID mutations found by our group and a similar proportion of all reported IL2RG mutations.

Amino Acid Sequence↗
PubMed1994

Infusions of donor leukocytes to treat Epstein-Barr virus-associated lymphoproliferative disorders after allogeneic bone marrow transplantation.

BACKGROUND: Lymphoma associated with Epstein-Barr virus (EBV) is a complication of bone marrow transplantation that responds poorly to standard forms of therapy. The lymphoma is usually of donor origin. We hypothesized that treatment with infusions of donor leukocytes, which contain cytotoxic T cells presensitized to EBV, might be an effective treatment. METHODS: We studied five patients in whom EBV-associated lymphoproliferative disorders developed after they received a T-cell-depleted allogeneic bone marrow transplant. Biopsy specimens were immunophenotyped, subjected to the polymerase chain reaction to determine the origin of the lymphoma (donor or host) and to detect the presence of EBV, and analyzed by Southern blotting for the presence of the clonal EBV genome and immunoglobulin-gene rearrangement. Patients were treated with infusions of unirradiated donor leukocytes at doses calculated to provide approximately 1.0 x 10(6) CD3+ T cells per kilogram of body weight. RESULTS: Histopathological examination of biopsy specimens from all five patients demonstrated monomorphic, malignant lymphomas of B-cell origin. Each of the four specimens that could be evaluated was of donor-cell origin. Evidence of clonality was found in two of the three samples adequate for study. EBV DNA was detected by the polymerase chain reaction in all five samples. In all five patients there were complete pathological or clinical responses. The responses were first documented histologically within 8 to 21 days after infusion. Clinical remissions were achieved within 14 to 30 days after the infusions and were sustained without further therapy in the three surviving patients for 10, 16, and 16 months. CONCLUSIONS: In a small number of patients, infusions of unirradiated donor leukocytes were an effective treatment for EBV-associated lymphoproliferative disease that arose after allogeneic bone marrow transplantation.

Adult↗
PubMed1994

Correction of neutropenia with rHuG-CSF after loss of response to rHuGM-CSF following autologous bone marrow transplant.

We describe a patient who presented with graft failure following autologous BMT, with an initial response of the neutrophil count to rHuGM-CSF but eventual loss of this response. Subsequently, this patient responded to rHuG-CSF. This could be explained by the fact that rHuG-CSF stimulates both early and late myeloid progenitor cells whereas rHuGM-CSF stimulates mainly the intermediate myeloid progenitor cells. This finding suggests that rHuG-CSF should be investigated for the treatment of patients with graft failure following ABMT.

Adolescent↗
PubMed1991

Characterization of the in vitro sensitivity of human lymphoid and hematopoietic progenitors to L-leucyl-L-leucine methyl ester.

L-leucyl-L-leucine methyl ester (LLME) is a lysosomotropic agent that in microMolar concentrations has been found to be selectively toxic to human and murine precursor and effector cytotoxic cells, irrespective of their surface membrane phenotype. We describe a new method of synthesis of LLME and evaluate the effects of this preparation on human lymphoid and hematopoietic progenitor cells. The new method of synthesis did not change the previously characterized activities of LLME. Consistent with previous observations, NK effectors, LAK precursors and effectors, and allospecific CTL (aCTL) effectors were completely ablated by treatment with 50-250 microM LLME, while the activities of helper T cells and B cells were preserved after treatments of up to 1000 microM LLME. The effects of LLME treatment on human marrow-derived erythroid, myeloid, and monocyte progenitors have not been previously described. We found that the growth of each of these committed precursors was reduced or eliminated following treatment with 100-250 microM LLME. Admixture of LLME-treated marrow with marrow depleted of T cells and other mature cellular elements resulted in increased growth of myeloid and erythroid colonies suggesting that cells that could provide colony-enhancing activities were preserved. In contrast to previous studies in humans, we found a minority of individuals to have aCTL precursors that were partially resistant to LLME. PBL from 10 of 15 individuals tested showed nearly complete ablation of aCTL precursors following treatment with 375 microM LLME. The remaining 5 individuals demonstrated significant aCTL precursor activity after identical treatment. The resistance to LLME was restricted to aCTL precursors, and neither increasing the dose of LLME nor prolonging the time of treatment completely overcame the resistance. The pattern of susceptibility (sensitive versus resistant) was found to be independent of the degree or type of HLA disparity between responder and stimulator. LLME-treated cultures with and without CTL activity contained a predominance of CD4+ T cells. However, in the subjects tested LLME-resistant aCTL was shown to be CD8+. In vitro priming of aCTL precursors from sensitive individuals did not consistently result in the development of resistance to LLME. These data indicate that further studies are needed to evaluate the effects of LLME on human stem cells and to determine the potential role of resistant aCTL precursors in GvHD prior to application of this technique as a form of selective T cell depletion in humans.

Antibody Formation↗
PubMed1990

B-cell differentiation following autologous, conventional, or T-cell depleted bone marrow transplantation: a recapitulation of normal B-cell ontogeny.

The circulating lymphocytes of 88 consecutive patients following autologous, conventional, or T-cell depleted bone marrow transplantation were serially analyzed for B-cell surface antigen expression and function. In the majority of patients, except for those who developed chronic graft-versus-host disease, the number of circulating CD20+ B cell normalized by the fourth posttransplant month. The earliest detectable B cells normally expressed HLA-DR, CD19, surface immunoglobulin (slg), CD21, Leu-8, and lacked expression of CD10 (CALLA). In addition, the circulating B cells expressed CD1c, CD38, CD5, and CD23 for the first year following transplant, antigens that are normally expressed on a small percentage of circulating B cells in normal adults, but highly expressed on cord blood B cells. Similar to cord blood B cells, patient B cells isolated during the first year following transplant, proliferated normally to Staphylococcus aureus Cowan strain I (SAC), and produced IgM, but minimal or no IgG when stimulated with pokeweed mitogen and SAC, unlike normal adult B cells that produce both. The similar phenotype and function of posttransplant and cord blood B cells, and their similar rate of decline in patients and normal children adds further evidence to support the hypothesis that B-cell differentiation posttransplant is recapitulating normal B-cell ontogeny.

Adult↗
PubMed1990

Absence of interleukin 2 production in a severe combined immunodeficiency disease syndrome with T cells.

We have characterized a child with a severe combined immunodeficiency disease syndrome with increased numbers, but a normal distribution, of CD3+ T cells. This patient's immunological defect appears to be attributable to a selective deficiency in T cell production of IL-2, which may reflect a subtle abnormality in the IL-2 gene locus or a defect in a regulatory factor necessary for IL-2 transcription. The increased numbers of phenotypically normal T cells in this patient suggest that alternative pathways of T cell development exist in man or that IL-2 production intra- and extrathymically is controlled via distinct regulatory mechanisms.

Antigens, CD↗
PubMed1990

Cytotoxic and proliferative T-cell clones with antidonor reactivity from a patient transplanted for severe combined immunodeficiency disease.

Patients who have become split lymphoid chimeras (T cells of donor origin, B cells and monocytes of host origin) following transplantation of HLA-haploidentical marrow for the treatment of severe combined immunodeficiency disease provide a unique model for the study of tolerance. One such patient, UPN 345, was transplanted with maternal marrow and was found to have antidonor proliferative reactivity without detectable donor-directed cytotoxicity when tested at 18, 23, and 66 mos following bone marrow transplantation. In bulk culture, the proliferation to donor cells could be blocked by monoclonal antibodies to HLA-DR and -DQ. Nine clones with antidonor reactivity were established by limiting dilution techniques from a mixed lymphocyte culture between engrafted T cells and irradiated donor E rosette-negative cells. All of the clones were of maternal donor origin, and all were CD3+CD4+CD8-. The clones were tested for proliferative and cytotoxic activity toward donor, host, and paternal B-lymphoblastoid cell lines (B-LCL). Six clones proliferated strongly to maternal B-LCL but not to host B-LCL. Six clones were found to exclusively lyse maternal B-LCL. Four of the clones had both antidonor cytotoxic and antidonor proliferative reactivity. Monoclonal antibody blocking studies were performed on five of the six clones with cytotoxic activity. The antidonor cytotoxicity was not inhibited by monoclonal antibodies to class I determinants; however, three clones were inhibited in the presence of monoclonal antibody to DR, one clone was inhibited by anti-DQ monoclonal antibody, and one clone was inhibited by anti-DP monoclonal antibody. The cytotoxicity of all five clones was inhibited by monoclonal antibody to CD4. These data indicate that antidonor reactivity may also include a cytotoxic component which is not apparent in bulk cultures and which, based on our limiting dilution studies, is probably controlled by regulatory cells. Both the antidonor cytotoxicity and the antidonor proliferation appear to be directed primarily toward donor HLA class II antigens that are not shared with the patient.

Adult↗
PubMed1990

Differential expression and regulation of the human CD8 alpha and CD8 beta chains.

The CD8 glycoprotein is expressed by thymocytes, mature T cells and natural killer (NK) cells and has been implicated in the recognition of monomorphic determinants on major histocompatibility complex (MHC) Class I antigens, and in signal transduction during the course of T-cell activation. Both human and rodent CD8 antigens are comprised of two distinct polypeptide chains, alpha and beta. The majority of monoclonal antibodies (mAb) reactive with the human CD8 antigen bind the CD8 alpha chain, while a single mAb, T8/2T8-5H7, has been identified which binds to the CD8 alpha/beta heterodimer. While the two chains of CD8 have been presumed to be coordinately expressed in normal T cells, this is not always the case. Northern blot analysis of a panel of T-cell leukemias and normal cells demonstrate that CD8 alpha and CD8 beta are not invariably co-transcribed and phenotypic analysis of fresh and interleukin 2 (IL-2) expanded peripheral blood mononuclear cells (PBMC) confirm that the CD8 alpha and CD8 beta chains are differentially expressed at the cell surface. Four distinct subpopulations of CD8+ cells have been identified based on the expression of CD8 alpha/alpha or CD8 alpha/beta complexes: (1) T-cell receptor (TcR) alpha beta+ T cells which are CD8 alpha+/beta+; (2) TcR alpha beta+ T cells which are CD8 alpha+/beta-; (3) TcR gamma delta+ T cells which are CD8 alpha+/beta- and (4) natural killer (NK) cells which are CD8 alpha+/beta-. We also demonstrate the down-regulation of the CD8 alpha/beta heterodimers from the surface of a CD8+ T-cell clone following treatment with phorbol myristate acetate (PMA) while CD8 alpha/alpha homodimers remain on the cell surface. This observation demonstrates that a) a CD8+ T-cell clone can express both CD8 alpha/alpha homodimers and CD8 alpha/beta heterodimers and b) these two complexes do not have identical biological properties. Together, these data suggest that CD8 alpha/alpha and CD8 alpha/beta dimers may not subserve identical functions. The differential contribution of these two CD8 complexes should be considered in models of T-cell-mediated cytotoxicity and T-cell activation.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1989

Graft failure after T-cell-depleted human leukocyte antigen identical marrow transplants for leukemia: II. In vitro analyses of host effector mechanisms.

To identify mechanisms potentially contributing to graft failure, 19 leukemic recipients of T-cell-depleted marrow transplants who failed to engraft following a transplant of HLA identical sibling marrow depleted of T cells by soybean agglutinin (SBA) and sheep erythrocytes (E) were evaluated. Peripheral blood mononuclear cells isolated at the time of failure were consistently of host origin, bearing the phenotype of suppressor T cells (CD3+, CD8+, Leu 7+). A direct cytolytic effect on 51Cr-labeled donor-derived target cells was not detected, a finding that contrasts with the donor-specific cytotoxic host T lymphocytes that have been regularly observed in patients rejecting HLA nonidentical SBA -E- BMTs. However, these host T cells did exhibit a strong and specific suppressive activity against the donor marrow CFU-GM in vitro. Furthermore, in contrast to prior findings in durably engrafted recipients of SBA -E- BMTs, the lymphocytes isolated prior to or at the time of graft failure lacked natural killer surface antigen expression and effector function.

Antigens, Surface↗
PubMed1989

Characterization of B cells in severe combined immunodeficiency disease.

The circulating lymphoid cells of eight consecutive untreated infants with severe combined immunodeficiency disease (SCID) with B cells were analyzed for surface marker expression and function. The B cells of these children expressed sIg, HLA-DR, CD19 (B4), CD20 (B1), CD21 (B2), Leu-8, and lacked expression of CD10 (CALLA), as do normal peripheral blood B lymphocytes. SCID B cells also expressed antigens that are normally absent or present on only a minor subset of circulating adult B lymphocytes, including CD1c (M241), CD38 (OKT10), CD23 (PL13), with or without concomitant CD5 (Leu-1) expression. The B cells of these children were capable of proliferating in vitro when stimulated with Staphylococcus aureus Cowan I. However, in the presence of pokeweed mitogen, S. aureus Cowan I, and normal T cells, the sIg+ cells of these children produced only IgM. Studies performed on normal B cells obtained from cord blood, young children, and adults reveal that whereas cord blood B cells are predominantly CD1c, CD38, and CD23 positive, B-cell expression of these antigens decreases with age. Cord blood B cells, similar to SCID B cells, produce only IgM when stimulated in vitro with pokeweed mitogen and S. aureus Cowan I. Based on these observations, we hypothesize that SCID B cells represent a population of B cells present during normal B-cell ontogeny which becomes a minor subset when an individual develops full immunologic competence.

Antibodies, Monoclonal↗
PubMed1989

Immune reconstitution following bone marrow transplantation: comparison of recipients of T-cell depleted marrow with recipients of conventional marrow grafts.

The reconstitution of hematopoietic cells and in vitro assays of immunologic function have been followed in leukemic patients after conventional bone marrow transplantation (BMT) (N = 34) and T-cell depleted BMT (N = 52) from human leukocyte antigen (HLA)-identical sibling donors. No effects of the T-cell depletion could be seen on the recovery of myeloid or lymphoid cells as measured by the day to engraftment or by the absolute number of cells through day 100. Normal numbers of lytically active natural killer cells returned the earliest and were rapidly followed in both groups of patients by the appearance of circulating B cells and normalization of the responses to B-cell mitogens. However, the recovery of normal T-cell proliferative responses were more delayed in recipients of T-cell depleted grafts. Significant quantitative differences were seen only during the first 3 months after transplantation. Neither the number of CD3+ T cells nor the ratio of CD4:CD8 positive cells differed markedly between the two transplant groups. Mitogen-induced immunoglobulin production by peripheral blood lymphocytes (PBL) from patients following T-cell depleted BMT was quantitatively less than that of conventional marrow recipients through the first year, with low normal IgM production reached by 4 to 6 months in both groups. IgG production reached low normal 7 to 9 months after conventional BMT but did not remain at this level until 1 year following either type of transplant. Assessment of the incidence of infections from the day the absolute neutrophil count reached 500 until day 180 after transplant revealed no significant differences between the two groups; indeed, the overall nonleukemic mortality was higher in the recipients of conventional bone marrow. Thus, in our series, the removal of mature cells from the marrow graft did not affect the rate or degree of recovery of myeloid and lymphoid cells but did affect the regeneration of in vitro T-cell dependent functions. We noted early quantitative differences and a delay in the normalization of the T-cell functions measured rather than prolonged absolute deficiencies. The in vitro deficiencies did not result in significant clinically apparent differences between the two groups.

Adolescent↗
PubMed1989

The use of HLA-non-identical T-cell-depleted marrow transplants for correction of severe combined immunodeficiency disease.

Since the introduction of methods for depleting T lymphocytes from human allogeneic marrow grafts in 1980, such transplants have been increasingly used as a source of lymphoid progenitors for the curative treatment of patients with lethal genetic disorders of immunity who lack an HLA matched sibling donor. This review of the results of HLA-haplotype disparate T-cell depleted marrow grafts applied to the treatment of severe combined immunodeficiency (SCID) indicates that such transplants can lead to durable engraftment and successful reconstitution of immune function without severe graft vs. host disease in a high proportion of cases. Resistance to engraftment and selective abnormalities of B cell development and function in the post transplant period constitute major obstacles to the success of these transplants. However, considerable progress has been made towards the elucidation of the cellular mechanisms responsible for graft resistance, graft-host tolerance and either the full or limited immunologic reconstitutions achieved.

Animals↗
PubMed1988

lambda PMV: a bacteriophage vector allowing single-step retrieval of cDNAs following expression in mammalian cells.

A general strategy has been developed for expression and rescue of cDNAs in mammalian cells. cDNA libraries are constructed in a new phage vector, lambda PMV, which contains simian virus 40 (SV40) early region promoter sequences for transcription of cDNA inserts, as well as a dominant-acting selectable marker neo. Efficient transfer of the cDNA library to mammalian cells can be achieved by phage particle-mediated transfection. Following selection in the antibiotic G418, cells expressing the phenotype of interest are identified and isolated. Rapid recovery of the transfected cDNA is achieved through cell fusion of the transduced cells with COS cells. Replication at the SV40 origin promotes excision of the integrated cDNA as small circular DNA, which after isolation in this form is used to transform bacteria to ampicillin resistance. To test this strategy, a cDNA encoding the human lymphocyte differentiation antigen CD8 was inserted into lambda PMV. CD8 expression on the surface of mouse L cells and the efficient recovery of full-length CD8 cDNA inserts confirm the feasibility of this system. It is anticipated that the single-step screening of libraries constructed in lambda PMV will allow for the isolation of rare cDNAs and will prove less laborious than methods currently available.

Bacteriophages↗