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Biomedical subjects

M Rowe

Publications and source records attributed to M Rowe.

At least 109 records · Page 6Linked to original sources
PubMed1984

T-cell-mediated regression of "spontaneous" and of Epstein-Barr virus-induced B-cell transformation in vitro: studies with cyclosporin A.

The regression of Epstein-Barr (EB) virus-transformed B-cell outgrowth which is seen in experimentally-infected cultures of blood mononuclear (UM) cells from healthy seropositive donors can be abolished in medium containing the T-cell-suppressive agent cyclosporin A (CSA) at concentrations of 0.05 microgram/ml and above. CSA mediates its effect within the first 4 days post-infection of the UM cells and this prevents subsequent in vitro generation of the EB virus-specific cytotoxic-T-cell response which normally brings about regression. Regression can be fully restored by supplementing the CSA-treated culture with interleukin 2 (IL-2)-containing culture supernatants or indeed with purified IL-2 itself, suggesting that CSA mediates its effect in this system through inhibiting the endogenous production of IL-2 which is required to amplify the virus-specific cytotoxic response. "Spontaneous transformation" to EB virus genome-positive lymphoblastoid cell lines in noninfected cultures of UM cells from healthy seropositive donors, though rare in normal medium, is enhanced to such a degree in the presence of CSA that, for many donors, the phenomenon becomes titratable against input cell dose across the 2.0 X 10(6)-2.5 X 10(5) cells/culture range. Cell mixing experiments suggest that the spontaneously transformed cell lines which arise with such efficiency under these conditions do so not by direct in vitro outgrowth of progenitor cells transformed by the virus in vivo, but by a two-step mechanism involving virus release and secondary infection in vitro.

B-Lymphocytes↗
PubMed1983

Heparin prevents formation of the human C3 amplification convertase by inhibiting the binding site for B on C3b.

Fluid-phase heparin prevents generation of the C3 amplification convertase of human complement, C3b, Bb most likely by inhibiting the formation of the bimolecular complex between cell-bound C3b and B. The effect of heparin on the binding of B to C3b was examined using 125I-labelled B and C3b-bearing sheep erythrocytes (EsC3b). In the absence of heparin, B bound to EsC3b with an affinity of 0.5-1 X 10(6) M-1 in the presence of 5 mM Mg2+. Incremental amounts of heparin (100-700 micrograms/10(7) EsC3b) inhibited the binding of 125I-B to C3b in a dose-dependent manner. Scatchard analysis of the binding data in the presence of four inhibitory concns of heparin revealed that heparin did not affect the binding affinity of B for C3b but decreased the number of C3b sites recognized by B on the cells. No inhibition of binding occurred in the presence of totally (N- and O-) desulfated heparin which has no anticomplementary activity. These results demonstrate that heparin prevents generation of the C3 amplification convertase by binding to cell-bound C3b and masking the binding site for B on C3b.

Animals↗
PubMed1983

Selective reactivation of Epstein-Barr virus-specific cytotoxic T cells by stimulation in vitro with allogeneic virus-transformed HLA-homozygous typing cells.

Epstein-Barr (EB) virus-specific cytotoxic T-cell preparations, produced by stimulation in vitro of peripheral blood lymphocytes with the autologous virus-transformed cell line, are HLA-A and B antigen-restricted and, with some donors, show preferential restriction through one or two of the four relevant antigens of the donor's HLA type. It has now been demonstrated that such EB virus-specific cytotoxic T cells may also be reactivated by stimulation with allogeneic virus-transformed cells provided that there is no mismatch of the HLA-A and B antigens between the responder and stimulator cell donors. In particular, virus-transformed cell lines from HLA-homozygous donors HLA-A and B antigen-matched to one of the haplotypes of an HLA-heterozygous responder were shown to reactivate selectively only those EB virus-specific cytotoxic T cells restricted through the HLA-A and B antigens present on the allogeneic stimulating cells. In addition to confirming the polyclonal nature of the HLA-restricted EB virus-specific cytotoxic T-cell response, this new experimental procedure has allowed the production, and subsequent expansion as cell lines dependent upon T-cell growth factor, of those effector cells restricted through the "nonpreferred" HLA antigens that are poorly represented in the response induced by stimulation with autologous virus-transformed cells.

Cell Line↗
PubMed1982

Monoclonal antibodies to Epstein-Barr virus-induced, transformation-associated cell surface antigens: binding patterns and effect upon virus-specific T-cell cytotoxicity.

Spleen cells from mice immunized with Epstein-Barr virus-transformed lymphoblastoid cells (EB-LCL) were used to generate monoclonal antibodies to cell surface antigens associated with the EB virus-transformed state. Radioimmune and immunofluorescence binding assays identified two antibodies, MHM6 and AC2, which reacted consistently with all EB-LCL tested, with a subpopulation of cells in some but not all EB virus genome-positive Burkitt lymphoma lines, but with none of a range of EB virus genome-negative cell lines of lymphoma or leukaemia origin. While MHM6 appeared to bind an EB virus-related antigen, AC2 bound some other cell surface antigen which was also found on a small subpopulation of cells in lymphocyte cultures stimulated with phytohaemagglutinin or with pokeweed mitogen. MHM6 and AC2 recognized single polypeptides with apparent molecular weights of 45 kd and 80 kd respectively as shown by sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis of 125I-labeled cell surface polypeptides immunoprecipitated with these antibodies. These polypeptides were induced on experimentally-infected B cells within 24 h of the expression of the EB virus nuclear antigen, EBNA, at a time known to coincide with the appearance of the lymphocyte-detected membrane antigen, LYDMA. However, saturating concentration of MHM6 and AC2 were unable to protect EB-LCL target cells from lysis by LYDMA-specific cytotoxic T cells in a chromium-release assay.

Animals↗
PubMed1982

Cytotoxic T cell recognition of Epstein-Barr virus-infected B cells. III. Establishment of HLA-restricted cytotoxic T cell lines using interleukin 2.

Epstein-Barr virus (EBV)-specific cytotoxic T cell precursors, present in the circulation of previously infected (seropositive) individuals, have been reactivated in vitro by challenging with autologous EBV-transformed cells, and the reactivated populations subsequently expanded as interleukin 2 (IL2)-dependent cell lines. These lines were dominated by T cells possessing the cytotoxic/suppressor cell surface phenotype and, when tested for effector function in chromium-release assays, demonstrated potent EBV-specific, HLA-A and -B antigen-restricted cytotoxicity even when derived from seropositive donors whose initial cytotoxic response to in vitro reactivation was relatively weak. With all the lines tested from 10 seropositive donors, strong killing of autologous EBV-transformed cells was observed in the absence of any significant lysis of autologous mitogen-stimulated lymphoblasts or of a panel of EBV genome-negative cell lines sensitive to natural killing. Furthermore, the availability of IL2-expanded effectors cell populations allowed their being tested upon a wide panel of allogeneic EBV-transformed targets such that the dominant HLA-restricted reactivities within these populations could be identified. Monoclonal antibody blocking experiments confirmed that lysis of the autologous EBV-transformed cell line by IL2-expanded effectors could be specifically inhibited (a) by pretreatment of the target cells with antibodies binding to the HLA/beta 2-microglobulin complex, and (b) by pretreatment of the effector cells with the cytotoxic/suppressor T cell-specific antibody Leu 2a.

Adult↗
PubMed1981

Reactivation of Epstein-Barr virus-specific cytotoxic T cells by in vitro stimulation with the autologous lymphoblastoid cell line.

Unfractionated mononuclear (UM) cells and T cells freshly prepared from the blood of adult donors were co-cultivated in microtest plate wells with progressively lower numbers of cells from the autologous EB-virus-transformed B-cell line. The fresh cells present in co-cultures from EB virus antibody-negative (seronegative) donors regularly facilitated autologous cell line outgrowth, monitored after 4 weeks, whereas outgrowth was markedly inhibited in the corresponding co-cultures from seropositive donors. Larger-scale co-cultures, set up at a ratio of 80-100 fresh UM cells to one autologous virus-transformed B cell, were harvested after 8 to 12 days and the T-cell subpopulation was examined for cytotoxicity both by growth inhibition and by chromium release assays. Cytotoxic T cells were generated exclusively in seropositive donor co-cultures and were strongly active against the autologous virus-transformed cell line without affecting either autologous uninfected B cells or any of a range of EB virus genome-negative target cell lines chosen as sensitive indicators of non-specific cytotoxicity. Recognition of allogeneic EB-virus-transformed cells was restricted to those whose HLA-A and/or B and/or B and/or C antigen expression matched that of the effector cells themselves;; moreover target cell lysis was specifically inhibited in the presence of monoclonal antibodies binding to these HLA antigens. The results indicate that EB-virus-specific HLA-restricted memory T cells, present in the blood of previously-infected individuals, can be reactivated in vitro using the established autologous virus-transformed cell line as a stimulus. THe reactivated cytotoxic cells appear to recognize a virus-induced lymphocyte-detected membrane antigen, LYD-MA, analogous to that first invoked to explain the cytotoxic response to primary EB virus infection observed during infectious monoucleosis.

Adult↗
PubMed1981

The effect of sympathetic nerve stimulation on responses of cutaneous pacinian corpuscles in the cat.

In the cat electrical stimulation of the distal segments of transected sympathetic nerves to the forelimb produces either an increase or a decrease in the responsiveness of the Pacinian corpuscles under the glabrous skin of th forepaw when the corpuscles are stimulated with high frequency mechanical vibration. The minimum latency of the change in Pacinian response is about 1-2 sec. As these effects could be stimulated by reduction in the forelimb blood supply it is probable that the changes in cutaneous corpuscle responsiveness following sympathetic stimulation are caused by local changes in blood flow.

Animals↗
PubMed1981

Bioavailability of 11 quinidine formulations adn pharmacokinetic variation in humans.

The bioavailabilities of eight quinidine sulfate, two gluconate, and one polygalacturonate formulations were compared, with one of the sulfate formulations as a reference (R) in a panel of 24 volunteers, according to a design comprising duplicate 6 x 6 Latin squares in two subject groups. Only one gluconate formulation (H) gave a significantly lower (p less than 0.05) area under the curve from 0 to 30 hr (AUC30), 90% or R, which was not as significant as AUC infinity (94% of R). Formulation H also gave a significantly lower peak concentration (Cmax) and a longer time to peak concentration (tmax) and generally exhibited some characteristics of sustained-release product. In addition, one product (F) gave a significantly higher Cmax while another formulation (D) gave a longer tmax. The wide range of dissolution times obtained with these products with three test conditions was not reflected in the AUC, Cmax, or tmax values obtained, except the Formulation H was consistently the slowest to dissolve. The terminal rate constants, expressed as t 1/2, of the 24 subjects gave an overall mean of 7.49 +/- 0.77 hr and ranged from 6.24 +/- 0.28 to 0.49 +/- 0.90 hr in individuals. The estimated total body clearance, with the assumption that the oral bioavailability was 70%, gave an overall mean of 4.22 +/- 1.05 and ranged from 2.49 +/- 0.28 to 6.42 +/- 0.70 mg/min/kg in individuals, demonstrating the wide range of quinidine disposition even in healthy subjects; this finding is in agreement with recently published results.

Adult↗
PubMed1980

Lymphocyte 5'-nucleotidase in primary hypogammaglobulinaemia and cord blood.

The 5'-nucleotidase (5'-N) deficiency on circulating mononuclear cells of patients with 'common variable' hypogammaglobulinaemia (CV-H) was shown to be the result of one or more of three factors: reduced T cell 5'-N activity, a reduced percentage of circulating B cells, and a low B cell 5'-N activity. A lack of circulating B lymphocytes, together with a low T cell 5'-N activity in some cases, was found to be responsible for the deficiency of lymphocyte 5'-N in patients with X-linked hypogammaglobulinaemia (X-H). The low levels of 5'-N activity in CV-H and X-H patients were not due to abnormal compartmentalization of the enzyme, altered enzyme kinetics, or the presence of a regulatory factor. Cord Blood B and T cells have a lower 5'-N activity than adult lymphocytes. The patient and cord blood data are discussed in relation to the stage of cellular maturity.

Adolescent↗