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Biomedical subjects

H G Prentice

Publications and source records attributed to H G Prentice.

At least 235 records · Page 13Linked to original sources
PubMed1986

T-cell depletion of allogeneic bone marrow prevents acceleration of graft-versus-host disease induced by exogenous interleukin 2.

Highly purified human recombinant interleukin 2 (IL-2) markedly accelerated lethal GVHD in the H-2-identical B10.BR----CBA combination, but had no effect when the donor cells were depleted of mature (Thy-1.2-positive) T lymphocytes, indicating a strong immunopotentiating effect of IL-2 on mature T cells causing GVHD. In the same donor-host combination, IL-2 did not influence the recovery from the post-transplantation bone marrow aplasia. The results suggest that IL-2 could be considered for adjuvant hormonal therapy to enhance immune recovery in recipients of T-cell-depleted allogeneic marrow.

Animals↗
PubMed1986

A515U: a prodrug of acyclovir with increased oral bioavailability.

The tolerance and pharmacokinetics of A515U, a xanthine oxidase-activated prodrug of acyclovir have been investigated in healthy volunteers and in two phase-I clinical studies in immunocompromised patients. In all cases the bioavailability of acyclovir following oral administration of A515U was substantially increased over that achieved in the same subjects with oral acyclovir itself. Plasma acyclovir levels were similar to those previously attainable only with intravenous acyclovir. This increase in bioavailability may permit reductions in the frequency of administration and extend the range of herpes virus infections amenable to oral therapy. A515U was very well tolerated, with no significant clinical adverse events being attributed to the drug.

Acyclovir↗
PubMed1986

The contribution of large granular lymphocytes to B cell activation and differentiation after T-cell-depleted allogeneic bone marrow transplantation.

Immunoglobulin and specific antibody levels are well maintained in the recipients of T-cell-depleted allogeneic bone marrow transplants (BMT), even though up to 99% of mature T cells are removed from the donor graft. For 3-8 weeks after the procedure, natural killer (NK) cells with an activated pattern of target cell killing have been shown to circulate in the recipient. This study investigates whether these recipient NK cells spontaneously secrete lymphokines that modulate B cell function in a way analogous to that of in-vitro-activated NK cells from normal individuals. Large granular lymphocytes (LGLs) (which contain a high proportion of NK cells) have been prepared from the peripheral blood of 11 recipients of T-cell-depleted major-histocompatibility-complex-matched allografts. In the first 4-6 weeks after BMT these LGLs were found spontaneously to secrete interleukin 2, interferon gamma and B cell differentiation factor. While secretion of these factors declines by 20-24 weeks after BMT, the quantities are still greater than those seen from control donors. Patient LGLs are also able to activate autologous (donor) B cells, rendering them potentially responsive to the secreted factors. It appears likely that activated NK cells (or LGL) play a significant role in maintaining B cell function in vivo after T-cell-depleted BMT.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1986

The significance of host haemopoietic cells detected by cytogenetic analysis of bone marrow from recipients of bone marrow transplants.

Bone marrow from 39 patients who received a bone marrow transplant (BMT) from a matched donor of different sex were studied by chromosome analysis for evidence of mixed haemopoietic chimaerism (MC). Recipient metaphases were detected in the bone marrow of 10 patients after BMT. Patients in whom MC was detected within 6 weeks of BMT did not all have a poor outcome. Two of seven are disease-free survivors at greater than 470 and greater than 632 d. All three patients in whom MC was diagnosed more than 6 weeks after BMT subsequently relapsed. Four factors appear to be important in determining the probability of relapse when MC is detected in a patient after BMT: the timing of detection of residual recipient cells; the proportion of these cells in the bone marrow; persistence of these cells in increasing proportions; and the karyotype of the recipient metaphases detected. Cytogenetic assessment may provide the earliest indication of relapse in these patients. In addition, this study provides further evidence that cyclophosphamide and total body irradiation, as used in these patients, may be inadequate conditioning therapy for BMT.

Adolescent↗
PubMed1986

Natural killer cell activity following T-cell depleted allogeneic bone marrow transplantation.

We have examined the recovery of natural killer (NK) cell function in seven recipients of MHC matched T cell depleted bone marrow allografts. NK cell activity against the erythroblastoid line K562 recovers 2-3 weeks after transplantation. Recipients also show a high level of killing of the T cell target HSB2 and of EBV transformed lymphoblastoid cell lines (B-LCL). This activity peaks at 4-6 weeks and declines towards normal by 12-14 weeks after transplantation. Although killing of HSB2 and B-LCL is usually the property of activated NK cells, few of these patients had any obvious 'trigger' of such activation: none had CMV infection, there were no episodes of graft rejection, and only two patients had mild and transient grade I graft versus host disease (GvHD). We conclude that T cell depletion does not affect the reconstitution of NK cell function and that NK cell activation occurs after T depleted bone marrow transplantation even in the absence of clinically detectable GvHD, graft rejection or CMV infection.

Adolescent↗
PubMed1986

Graft rejection following HLA matched T-lymphocyte depleted bone marrow transplantation.

Bone marrow graft rejection following HLA-matched bone marrow transplantation (BMT) for leukaemia has been a rare problem. However, with the introduction of T-lymphocyte depleted BMT, graft rejection is recognized as a new complication. At the Royal Free Hospital (RFH) in London T-depletion is achieved using two monoclonal antibodies with complement mediated lysis. The methodology was extended to other centres and in total 56 patients have received T-depleted, HLA matched BMT. Twelve of 56 patients have had graft rejection. At the RFH three of 41 (7%) patients have had rejection whereas at collaborating centres nine of 15 (60%) patients have had rejection. We have investigated these rejections in order to identify factor(s) responsible. Rejection was not restricted by patient or donor characteristics, nor disease status. Patient management, chemotherapy conditioning, efficiency of T-depletion, graft versus host disease (GvHD), and infection post BMT, were not consistently implicated. The major difference between the RFH and all other centres was in the radiotherapy (RT) conditioning: The RFH prescribed a single fraction of 7.5 Gy total body irradiation (TBI) whilst collaborating centres gave 10 or 12 Gy fractionated TBI. We conclude that the different incidence of rejection (7% v. 60%) relates primarily to the RT conditioning although the mechanisms(s) of rejection remain unknown. We conclude that where T-depleted BMT is used, compensation by more intensive RT conditioning is required in order to avert graft rejection.

Adolescent↗
PubMed1986

Production of anti-cytomegalovirus antibody following T-cell depleted bone marrow transplant.

The serological status to cytomegalovirus (CMV) was examined in 24 patients with no detectable CMV excretion, following T-lymphocyte depleted bone marrow transplantation. The results show that seropositive recipients continue to produce CMV antibody regardless of the serological status of the donor but that seronegative recipients fail to produce CMV antibody even when the donor is seropositive. These findings suggest that when an effective CMV vaccine becomes available vaccination of the donor would be unlikely to confer protection on the recipient but that vaccination of the recipient may achieve this.

Antibodies, Viral↗
PubMed1986

Standardization of T-cell depletion in HLA matched bone marrow transplantation.

The IBM 2991 Blood Cell Processor has been used to isolate a mononuclear cell (MNC) fraction from the marrow of 31 allogeneic donors. The MNC fraction was then incubated with a combination of two murine monoclonal antibodies MBG6 (CD6) and RFT8 (CD8) followed by two rounds of treatment with rabbit complement resulting in a marrow inoculum significantly reduced in the number of T-lymphocytes. We report here new specifications for the use of Ficoll-Metrizoate, the method used to calculate T-lymphocyte depletion and the details of our attempts to improve T-depletion. Following marrow transplantation with this T-depleted fraction, 29 patients are evaluable for engraftment, one patient failed to engraft and one died too early for evaluation. Twenty-two had no acute graft-versus-host disease (aGvHD), at a minimum of 60 d, six had grade I acute GvHD and one grade III. No correlation was found between the absolute number of MNC infused and time to engraftment, nor any relationship between the number of residual viable T-lymphocytes in the infused marrow and the incidence of GvHD, but the patient with the most severe aGvHD also had the highest number of T-lymphocytes infused.

Antibodies, Monoclonal↗
PubMed1986

Recovery of immunoglobulin isotypes following T-cell depleted allogeneic bone marrow transplantation.

After conventional bone marrow transplantation serum IgG, IgM and IgA levels fall from pre-transplant levels and may not return to normal for 3-12 months. In contrast IgE may rise to supranormal levels, an event that may be associated with graft-versus-host disease. We have investigated the recovery of immunoglobulin isotypes in the recipients of allogeneic marrows depleted of T-cells to prevent graft-versus-host disease. We find that pre-transplant IgG, IgM and IgA levels are maintained throughout the post-transplant period but that there is a short-lived rise in IgE about 3 weeks after transplantation: this rise occurs in the absence of clinically detectable graft-versus-host disease. We conclude that specific T-cell depletion does not impair and may actually enhance the functional recovery of B cells after allogeneic BMT.

Adolescent↗
PubMed1986

Standardization of the processing of human bone marrow for allogeneic transplantation.

Allogeneic bone marrow transplantation has been undertaken within this centre on 62 patients with acute or chronic leukaemia. Employing the standard separation protocol described, all bone marrows were processed on the 2991 Blood Cell Processor to isolate the 'buffy coat' cells and subsequently the mononuclear cell component using a density separation medium of Ficoll-metrizoate. Following the mononuclear cell separation, the cells were identified for their T lymphocyte component using a combination of two murine monoclonal antibodies, MBG6 reacting with a pan T cell antigen (CD6) and RFT8 detecting the 'cytotoxic/supressor' cell antigen (CD8). The numerical results for nucleated cells, red blood cells, T lymphocytes and colony forming units-granulocyte macrophage are presented.

Bone Marrow Transplantation↗
PubMed1986

Haemolysis after T-cell depleted bone marrow transplantation involving minor AB0 incompatibility.

9 recipients of T-cell depleted allogeneic bone marrows (8 group A, 1 group AB) from group 0 donors were monitored after transplantation. Free anti-A/B was demonstrable in 8 of the 9 recipients 10-19 d post-transplant, 5 patients developed a positive direct anti-globulin test and 7 showed a rise in bilirubin. The presence of antibody was generally unrelated to the infusion of incompatible plasma, although 2 patients who also received anti-CMV immunoglobulin subsequently shown to contain high titre IgG anti-A/B were more severely affected, sustaining a fall in Hb of up to 2 g/d. These observations suggest that, after T-cell depleted bone marrow transplantation, immunocompetent B lymphocytes of donor origin are transferred, secrete antibody in the recipient, and may be responsible for self-limiting haemolytic episodes.

ABO Blood-Group System↗
PubMed1986

Salivary amylase and pancreatic enzymes in serum after total body irradiation.

Amylase increases in serum after total body irradiation (TBI). To investigate whether this increase is ascribable to pancreatic or salivary amylase, or both, we measured the post-irradiation activity concentration of the three major pancreatic enzymes (trypsin, amylase, and lipase) and of salivary-type amylase in serum from six leukemic patients given TBI before bone-marrow transplantation. Salivary amylase increased by as much as 50-fold after TBI, peaking on the first day after the irradiation. The increase was associated with the development of clinical parotitis. Pancreatic trypsin, total amylase, and lipase increased inconsistently and to a much smaller degree. There were no associated clinical features of pancreatitis. Our data show that, at the dose of radiation given to our patients, there is no danger of pancreatitis as a complication, but parotitis is a consistent development after TBI.

Amylases↗
PubMed1986

T lymphocyte regeneration after transplantation of T cell depleted allogeneic bone marrow.

The regeneration of T cell subsets was studied with double immunofluorescence marker methods in 37 patients who received HLA matched T lymphocyte depleted bone marrow transplants (BMT) as part of the treatment for their haematological disease. A cocktail of anti-pan-T (CD6: MBG6) and anti-suppressor/cytotoxic-T cell (CD8: RFT8) monoclonal antibodies was used with rabbit serum as a source of cytolytic complement to achieve selective T cell lysis. The T8+ cells reached low normal values around 60 days post-transplant and remained within the normal range throughout the study (greater than 150 days). This observation is in contrast to our previously published results in patients who, after receiving BMT without efficient T cell depletion, had increased numbers of circulation T8+ cells from 60 days post-transplant. In the present study Leu-7+, RFT8- cells reached normal values rapidly but the reconstitution of T4+ lymphocytes was slow: low normal levels were reached only around day 150 following BMT. The degree of graft-versus-host disease (GVHD) seemed to be related to the number of residual T cells infused: two of the three patients who received the highest numbers of T cells developed Grade II III; otherwise GVHD was minimal. Among the clinical parameters studied cytomegalovirus (CMV) immune status moderately influenced reconstitution: at 55-90 days post-transplant T8+ cells were present at the upper normal levels in seven out of 15 patients receiving BMT from CMV seronegative donors, but in none of the 16 individuals receiving BMT from seropositive donors. CMV related complications were relatively uncommon. Thus the most significant factor in preventing 'T8+ cell overshoot' and T cell imbalance during regeneration appears to be the depletion of T (including T8+) lymphocytes from marrow. The differences of T8+ cell reconstitution in this and previous studies may reflect a different regeneration pattern from T cell precursors as opposed to inoculated mature T cells.

Adolescent↗
PubMed1986

The use of monoclonal antibodies in graft versus host disease prevention.

One of the most important causes of procedure related death after bone marrow transplantation (BMT) is graft versus host disease (GvHD) in which donor T-lymphocytes recognise alloantigens in the recipient and attack and damage the cells bearing them. Even when donor and recipient are matched at all loci of the major histocompatibility complex (MHC) 40%-70% of recipients develop severe graft versus host disease after conventional BMT: in a third of those affected the outcome is fatal. When donor and recipient are less than identical at the MHC the incidence and severity of acute graft versus host disease are correspondingly higher. The morbidity and mortality associated with acute GvHD has limited the application of bone marrow transplantation in two ways: first by restricting the procedure to patients with serious haematological disease and second by excluding individuals who might benefit from BMT but who lack an MHC identical sibling. In this review we discuss briefly the theoretical work that led us to our protocol for T-cell depletion for GvHD prevention and then describe the results of our own and other groups undertaking T-cell depleted bone marrow transplants. Finally, we discuss some of the new problems--and benefits--associated with T-cell depletion and outline the improvements in techniques now taking place.

Antibodies, Monoclonal↗