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Biomedical subjects

L Hudson

Publications and source records attributed to L Hudson.

At least 73 records · Page 4Linked to original sources
PubMed1985

Isolation and characterisation of human T-cell lines from a patient with Chagas' disease.

Short-term T-cell lines reactive to different Trypanosoma cruzi antigens were isolated from a patient with Chagas' disease. These T-cell lines were analysed phenotypically with monoclonal antibodies defining pan-T (T11), helper (T4), or cytotoxic/suppressor epitopes by the use of a continuous-flow microfluorimeter. One cell line, 5C3, was obtained from T-cell blasts reactive to formaldehyde-fixed amastigotes (the intracellular stage of the parasite) plated at limiting dilution (3.3 cells/well). This line was shown to be T11 and T4 positive, to respond to specific antigen in an HLA-DR restricted manner, and to produce interleukin-2 under similar growth conditions.

Antibodies, Monoclonal↗
PubMed1985

Alternative splicing accounts for the four forms of myelin basic protein.

We have isolated cDNA clones encoding the four different forms of mouse myelin basic protein (MBP) and have analyzed the structure of the MBP gene. The three larger forms of MBP differ from the smallest by the inclusion of either or both of two short amino acid sequences at positions 57 and 124 of the smallest protein. The mouse genome contains a single MBP gene comprised of seven exons. The two amino acid sequences present only in the larger MBPs are encoded by separate exons. Furthermore, all exons in the coding region begin or end in complete codons so that alternative splicing does not alter the reading frame. We conclude that the four forms of this myelin protein are encoded in separate mRNAs, each derived by a simple alternative splicing of the primary MBP gene transcript. Comparison of the amino acid sequence encoded by each exon with a recent model of the secondary structure of MBP suggests that each of the seven exons encodes one or two of the predicted structural motifs of the protein.

Amino Acid Sequence↗
PubMed1985

Antigen-specific lymphocyte transformation in congenital toxoplasmosis.

Secreted (TSA) and water lysed antigens (WLA) derived from cell culture of the RH strain of Toxoplasma gondii have been used to induce antigen-specific mitogenesis of lymphocytes from children with congenital toxoplasmosis. Responsiveness to WLA was variable, with all patients giving false negative results. Responses to TSA, however, were highly specific, with no false negatives. This increased specificity was not due to an increased response to TSA (P less than 0.001), but a lower TSA response by the lymphocytes of the uninfected subjects (P greater than 0.1), compared with WLA in both cases. Preliminary studies have shown that while WLA induces high levels of non-specific immunity, such as natural killing, TSA is able to induce specific killing of Toxoplasma in vitro through the action of activated macrophages; this may partially explain the increased specificity of TSA in the lymphocyte transformation test.

Adult↗
PubMed1985

Administration of adenosine diphosphate-ribosyl transferase antagonist allows in vivo control of anti-dinitrophenyl response.

3-Methoxybenzamide (3MB) is one of a series of chemical inhibitors of the nuclear enzyme adenosine diphosphate (ADP)-ribosyl transferase (ADPRT), which has been shown to inhibit cell differentiation in vitro, but has no effect on differentiation independent proliferation. Treatment of mice with an optimal concentration of 3MB (20 mg/kg body weight) at or 1 day after dinitrophenyl-keyhole limpet haemocyanin (DNP-KLH) immunisation reduced anti-DNP plaque-forming cell (PFC) numbers to less than 10% of those of control animals. The period for maximum PFC suppression showed a narrow time window relative to immunisation, suggesting that in vivo, as in vitro, 3 MB was acting only on those lymphocytes differentiating in response to antigen. Experimental findings showed that it was possible to select for PFC derived from different populations of DNP-responsive lymphocytes by adjusting the time of 3MB treatment relative to immunisation. When 3MB was used with antigen priming, the residual PFC showed a lower average affinity than PFC in mice treated with 3MB 3 days after priming, suggesting a differential selection of those lymphocytes responding either 'early' or 'late' in the primary immune response.

Animals↗
PubMed1985

Human and mouse sera recognize the same polypeptide associated with immunological resistance to Trypanosoma cruzi infection.

Effective immunological resistance to challenge with trypomastigotes of Trypanosoma cruzi has been linked to antibodies which are specific for determinants on live, but not fixed, trypomastigotes. In man and mouse, these antibodies can be detected specifically by viable immunofluorescence (VIF) and complement mediated lysis (CML) assays. VIF/CML positive sera from chagasic patients or experimentally infected mice recognize the same trypomastigote specific surface polypeptides of apparent Mr 70-160 kDa. VIF/CML negative chagasic sera fail to react with polypeptides of Mr 120, 145 and 160 kDa, whereas negative mouse sera lack antibodies to the 160 kDa component alone. Taken together, these clinical and experimental data suggest that the 160 kDa polypeptide should be tested for its potential in immunoprophylaxis.

Animals↗
PubMed1985

Adsorption of Trypanosoma cruzi proteins to mammalian cells in vitro.

It has previously been shown using immunological techniques that antigens from Trypanosoma cruzi adsorb to mammalian cells. Here we have used radioactively-labelled T. cruzi antigens to investigate the nature of the antigens bound. We have demonstrated that numerous T. cruzi polypeptides rapidly become adsorbed to mammalian cells in tissue culture. These polypeptides dissociate from the mammalian cells only at a slow rate. We found no indication that the binding of the polypeptides was mediated by the specific binding of any one protein.

Adsorption↗
PubMed1985

Antibody response to experimental Trypanosoma rangeli infection and its implications for immunodiagnosis of South American trypanosomiasis.

Differential immunodiagnosis of T. rangeli and T. cruzi infections in man poses a particular problem, not only because these parasites share antigenic determinants, as detected by immunofluorescence, but also because they have a similar geographical distribution, the same host range and often identical insect vectors. We show here that whereas mouse anti-T. rangeli sera have significant cross reactivity with T. cruzi by immunofluorescence, they are entirely specific when tested by ELISA, using apparently similar antigen preparations. Immunoprecipitation analysis detected relatively little cross-reactivity between heterologous antisera and parasite combinations. Intriguingly, immunization with T. rangeli epimastigotes was much more powerful than similar immunization with trypomastigotes, and the majority of the antibody was directed against a single polypeptide of apparent Mr 73kDa.

Animals↗
PubMed1985

The use of labetalol for the treatment of hypertension in patients with reversible airway obstruction.

Beta-adrenergic blocking agents are commonly used for the management of hypertension, cardiac arrhythmias, and angina pectoris; several of these agents are now available for clinical use (1-5). A significant side effect of these agents in patients experiencing reversible airway obstruction is that they block the effects of beta-adrenergic agonists and can precipitate or worsen bronchospasm (6-8). Labetalol, a new adrenergic antagonist with both alpha- and beta-adrenergic blocking effects, has been shown to have certain advantages for the management of hypertension and is widely used for this purpose in many countries (9). To evaluate its effects on airway resistance in patients with obstructive lung disease, the authors conducted two separate clinical studies. This article summarizes the results of these trials.

Airway Resistance↗
PubMed1985

Origin and immunological hyporeactivity of canine alveolar lymphocytes.

Autochthonous canine thoracic duct lymphocytes were isolated, labelled with 111indium and injected intravenously. Direct sampling showed that the label passed from blood to lymph within 25 hr. By gamma camera imaging, the initial accumulation of 111In the liver and spleen was followed by a striking increase in lymph node associated activity between 24-36 hr. Although initial lung-associated counts were low, a bicarbonate-induced non-specific inflammation of the right lung induced a rapid and selective accumulation of labelled lymphocytes (ratio right to left lung 8:1). Cell suspensions lavaged from the alveolar surface showed only a 9% response to phytohaemagglutinin (PHA) compared to peripheral blood lymphocytes (PBL). The addition of unfractionated lavage cells to PBL caused a macrophage-dependent suppression of mitogen responsiveness. However, macrophage depletion of alveolar lavage cells did not restore the lymphocyte response to PHA. Similarly, the frequency of alloreactive precursors of cytolytic lymphocytes (CTL) was almost 10-fold less in alveolar lymphocytes compared to PBL. Thus, bronchoalveolar lavage provides a technique by which viable cells may be recovered in significant numbers from the alveoli and should be invaluable for the investigation of lung allograft rejection.

Animals↗
PubMed1984

Immunological consequences of infection and vaccination in South American trypanosomiasis.

Trypanosoma cruzi infection provokes a vigorous immune response that terminates the parasitaemia associated with the acute stage within two to three months of initial infection. Even so, a variable proportion of patients may develop severe Chagas' disease, often decades after initial infection. Recent experimental findings suggest that trypomastigotes of T. cruzi possess a surface bound neuraminidase and sugar binding protein by means of which they invade host cells--a mechanism very reminiscent of influenza virus. Studies of the antibody response to trypomastigotes in patients or murine models have identified a series of antibodies able to mediate lysis of live parasites in a complement mediated lysis (c.m.l.) assay. These antibodies have also been linked to resistance to infection in vivo and disappear following successful parasitological 'cure' in drug-treated animals and human patients. Immunochemical studies have shown that sera from infected patients or mice lacking this c.m.l. activity also lack those antibodies able to bind trypomastigote surface components of 85 and 160 kDa relative molecular mass. The availability of rabbit and mouse models of Chagas' disease have produced data that suggest that chronic stage pathology may have an immunological basis dependent on the known cross reactivity between host and parasite cells. Delivery of the lethal hit leading to host cell destruction is probably facilitated by the ability of parasite antigens to bind to host cells thus exposing them to the host's own anti-parasite immune response. If Chagas' disease does indeed have an immunological basis, then this might be controlled in turn by immunoregulation, in a manner analogous to that achieved in experimental allergic encephalomyelitis.

Animals↗
PubMed1984

Inhibition of cell division and antibody secretion by murine alpha/beta interferon: effects on plasmacytoma and hybridoma lymphoid cells.

Murine alpha/beta interferon (IFN) inhibited the growth of myeloma cells in vitro. Independently of the cell growth inhibition, IFN also reduced the number of antibody secreting myeloma cells as measured by haemolytic plaque assay. The sensitivity of both MOPC 315 plasmacytoma cells and 4F4 hybridoma cells varied, though not to the same extent, depending on the dose of IFN used and the duration of exposure. Inhibition of PFC activity was observed after one day of IFN treatment while inhibition of cell growth was not detected until Day 2 of incubation. A dose of 20 u/ml IFN had no effect on the growth rate of MOPC 315 cells but with 100 u/ml the inhibition of growth was virtually complete. In contrast, an inhibition of PFC activity was observed at all the concentrations tested. The cell growth and PFC activity of 4F4 hybridoma cells, on the other hand, were both inhibited by IFN when used at concentrations as low as 1.25 u/ml. Incubation with higher concentrations of IFN resulted in a progressive reduction in cell growth and PFC activity of 4F4 cells, however to a lesser degree of inhibition compared to that observed with MOPC 315 cells. For example, although virtually 70% of MOPC 315 PFC could be inhibited by culture for two days in the presence of 100 u/ml, it was necessary to use 1,250 u/ml IFN for 4 days incubation before the similar level of PFC inhibition was achieved with 4F4 cells. IFN treatment resulted in an increase in both cellular volume and protein content and this effect was prevented when IFN was previously neutralised by a specific antiserum. IFN-treated cells also showed an inhibition in the incorporation of 3[H]-thymidine but no alteration in the rate of utilization of 35[S]-methionine, when compared with an equal number of control cells.

Animals↗
PubMed1984

Antigen specific lymphocyte transformation induced by secreted antigens from Toxoplasma gondii.

Secreted (TSA) and water lysed (WLA) antigens derived from cell culture of the RH strain of Toxoplasma gondii have been used to induce antigen specific mitogenesis of lymphocytes from patients with symptomatic and asymptomatic toxoplasmosis. Lymphocyte responsiveness to WLA was similar to previous reports, with about 50% of patients showing a false negative reaction. Responses to TSA however were highly specific, with no false negative reactions. This increased specificity was not due to an increased response against TSA by patients' lymphocytes (P less than 0.001), but a lower TSA response by uninfected subjects' lymphocytes (P greater than 0.1) compared with WLA in both cases. In a minority of both infected and uninfected subjects, there was a low but detectable response to antigens secreted by the host cell line (HCA), and this was directly compared to their responses against TSA. There was at least a 10-fold increase in the patients' responses to TSA when compared with HCA (P less than 0.001), whereas there was no significant difference between the uninfected subjects' responses to these antigens (P greater than 0.1). Preliminary observations have suggested that TSA is distinct from other defined secreted antigens as both heat treatment and solid phase immunosorption did not have any noticeable effect on TSA-induced mitogenesis.

Adolescent↗
PubMed1984

Trypanosoma cruzi: continuous cultivation with murine cell lines.

Y strain parasites (Wellcome stock) were cloned as epimastigotes by limiting dilution and one clone, Wel Tryp A2 was used to infect cell cultures and irradiated mice. The fibrosarcoma line, M4, was susceptible to infection with Wel Tryp A2 trypomastigotes but, after the first round of intracellular infection, proliferation and differentiation, failed to support parasite growth in long-term continuous culture. In contrast, a muscle-derived cell line, S2, produced regular waves of extracellular trypomastigotes and amastigotes during 80 days of continuous culture reported here. These infected S2 cultures have remained in continuous culture for up to 18 months over a 5-year period and have yielded in excess of 10(8) parasites/20 ml culture at 4-6 day intervals. Extracellular amastigotes produced in these cultures have a close morphological, immunological and biochemical analogy to intracellular parasites derived from rodents, and have maintained an absolute dependence on host cells for their growth and proliferation. These amastigotes produced low-grade chronic infections in normal CBA/T6 mice but produced acute, fatal infections with high parasitaemia in mice of the same inbred strain given 900 rad. whole-body irradiation prior to infection. Although present findings relate to a single parasite clone, the parent stock from which the clone was derived showed similar growth characteristics when co-cultured with S2 cells.

Animals↗