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Biomedical subjects

G F Mitchell

Publications and source records attributed to G F Mitchell.

At least 217 records · Page 12Linked to original sources
PubMed1979

Murine cutaneous leishmaniasis: disease patterns in intact and nude mice of various genotypes and examination of some differences between normal and infected macrophages.

The course of the disease, cutaneous leishmaniasis, caused by the intracellular protozoan parasite Leishmania tropica, differs markedly amongst various common inbred mouse strains. After intradermal injection of 1 x 10(6) promastigotes to young female specific pathogen-free (SPF) derived mice, persistent infection characterized by an expanding ulcerous lesion is seen in BALB/c and DBA/2 mice. In the strains CBA/H, C3H/He and A/J, lesions resolve within 8 weeks, and in C57B1/6 mice no real lesion typical of cutaneous leishmaniasis develops at the injection site. NZB mice are highly resistant. Macrophages harvested from the thioglycollate-stimulated peritoneal cavity of NZB and C57B1/6 mice appear to differ from macrophages of the other mouse strains in not supporting multiplication of L. tropica organisms in vitro. Nevertheless, hypothymic nude (nu/nu) mice of C57B1/6 genotype, as well as CBA/H-nu/nu and BALB/c-nu/nu mice, develop large lesions with metastases to other cutaneous and visceral locations. In the intact mice in which infection resolves spontaneously, resistance to reinfection is complete. Using mouse antipromastigote sera and an indirect fluorescent antibody test in carefully controlled experiments, L. tropica antigens were detected on in vitro infected macrophages of both highly susceptible BALB/c and relatively resistant CBA/H genotypes. After incubation with a crude soluble antigen preparation from cultured promastigotes, infected BALB/c macrophages differed from infected CBA/H macrophages (and uninfected macrophages of both genotypes) in being unable to sensitize syngeneic recipients for a delayed-type hypersensitivity response to that antigen. When infected and uninfected macrophages were used as "blocking cells" in an in vitro alloreactive cytotoxic T cell system involving cells from congenic mice, evidence was obtained for reduced H-2d expression on infected macrophages of the susceptible mouse strains, BALB/c. The data in this model system of cutaneous leishmaniasis raise the possibility that genetic susceptibility is associated with both a permissive macrophage and defective T cell recognition of parasite antigens on infected macrophages. Defective recognition may be the result of reduced functional expression of H-2d antigens on infected BALB/c macrophages required for efficient recognition by syngeneic T cells of one or more subpopulations.

Animals↗
PubMed1979

Hybridoma antibody immunoassays for the detection of parasitic infection: development of a model system using a larval cestode infection in mice.

A prototype immunodiagnostic assay has been developed using chronic infection with the larval cestode, Mesocestoides corti, as a model system in mice. The assay is highly sensitive, it appears to be absolutely specific for M. corti infection, and is based on the inhibition of binding (by sera from infected mice) of a radiolabelled anti-M. corti hybridoma antibody to a crude M. corti antigen extract. The hybridoma antibody binds to living M. corti larvae and is an IgG1 protein. In large scale experiments no false positives were detected and the only M. corti-infected mice not detected by the assay were hypothymic nude (nu/nu) mice. Only limited success has been achieved in attempts to convert the assay to one not requiring parasite antigen and based on the inhibition of binding of radiolabelled anti-parasite hybridoma antibody and a large pool of anti-idiotype antiserum. Monoclonal antibodies derived from anti-parasite antibody-secreting hybridoma cell lines will be of particular use in the development of new, highly specific, immunodiagnostic reagents for the detection of parasite infection, exposure and disease.

Animals↗
PubMed1979

Optimal conditions for lactoperoxidase catalyzed radioiodination of external proteins on mouse erythrocytes.

Optimal conditions were established for specific labelling of the surface proteins of mouse erythrocytes using lactoperoxidase-catalyzed radioiodination. The levels of H2O2 and I-, and cell concentrations required for restriction of haemoglobin labelling to less than 5% of the total 125I-protein, were different for radioiodination employing direct H2O2 addition or generation of H2O2 with glucose oxidase plus glucose. Preparation of mouse erythrocyte ghosts by hypotonic lysis caused loss of some minor labelled proteins present on intact cells and shifts to lower molecular weights of others. It is therefore important to solubilize labelled cells directly in electrophoresis buffer to avoid artifactual degradation of labelled proteins. The extent of labelling internal cell proteins was measured by a procedure suitable for the comparison of a large number of samples: solubilized radioiodinated erythrocytes were electrophoresed on 14% acrylamide gels and the radioactivity determined in the haemoglobin band which migrates separately from other proteins. The major labelled protein on the mouse erythrocytes had an apparent molecular weight of 92,000, and may be analogous to Band 3 of the human erythrocyte.

Animals↗
PubMed1979

IgG1 hypergammaglobulinaemia in chronic parasitic infections in mice: magnitude of the response in mice infected with various parasites.

Mice chronically infected with 3 metazoan and 1 protozoan parasite contain in their circulation levels of IgG1 which are increased over the levels in uninfected mice by at least 10x. In the case of infection with the larval cestode, Mesocestoides corti, the serum IgG1 concentration can reach greater than 50 mg/ml and, with a half-life of less than 2 days, the number of cells engaged in IgG1 production is approximately 2 x 10(8). The IgG1 hypergammaglobulinaemia is not seen in infected hypothymic nude mice. Biosynthetic labelling studies with organ and tissue cultures established that in two of the chronic infections the organs principally involved in IgG1 synthesis were those pathologically involved or those "in line" for antigen capture: i.e. liver and spleen in the case of M. corti which is located in the liver and the peritoneal cavity, and various intestinal lymph nodes in the case of the gut-dwelling nematode, Nematospiroides dubius. This apparently exaggerated response to chronic parasitic infection is of interest simply because of the potential magnitude of the effect and the fact that it involves an Ig isotype with very poorly defined biological function.

Animals↗
PubMed1979

IgG1 hypergammaglobulinaemia in chronic parasitic infections in mice: evidence that the response reflects chronicity of antigen exposure.

The IgG1 molecules in the sera of IgG1 hypergammaglobulinaemic mice chronically infected with the larval cestode, Mesocestoides corti, are a heterogeneous population. Although antibodies to M. corti are present, the question of whether a minority or majority of the serum IgG1 molecules has anti-parasite reactivity remains open. The splenic PFC response to an intravenous injection of SRBC in M. corti-infected mice does not consist of an unusually high proportion of IgG1 anti-SRBC PFC. Moreover, the adoptive anti-DNP PFC response of spleen cells from M. corti-infected mice to DNP-M. corti is not biased towards IgG1 antibody production. Since IgG1 hypergammaglobulinaemia is seen in mice with chronic, "high-dose" infections, an attempt has been made to simulate chronic antigenic exposure with SRBC in uninfected mice. A split, high-dose regime of SRBC injections leads to a high number and high proportion of IgG1 anti-SRBC PFC in the spleen in three strains of mice. The results suggest that the extraordinarily high levels of IgG1 seen in the sera of mice chronically infected with the metazoa, M. corti and Nematospiroides dubius, reflect persistent, high-dose, "strong", T cell-dependent stimulation of the B cell system.

Animals↗
PubMed1979

Immunoprecipitation of biosynthetically-labelled products in the identification of antigens of murine red cells infected with the protozoan parasite, Plasmodium berghei.

In this methodological paper an immunoprecipitation technique has been optimised for the identification of antigens of Plasmodium berghei-infected blood which react with antibody specificities in a host-protective antiserum. Extracted 3H-leucine biosynthetically-labelled products of infected blood were sequentially reacted and precipitated with sera from mice which had been exposed to P. berghei but which were either non-protected or protected against lethal infection, protection having been shown to be transferable to naive recipients with the appropriate serum. As analysed by polyacrylamide gel electrophoresis under reducing conditions, a small number of molecular species was detected in immunoprecipitates using host-protective sera which were apparently not quantitatively precipitated out of the complex mixture of labelled products of infected blood using sera from non-protected mice.

Animals↗
PubMed1979

The development of resistance in different inbred strains of mice to infection with Nematospiroides dubius.

Infection by the intestinal nematode parasite Nematospiroides dubius was studied in seven different inbred mouse strains. Although there was some minor variation in the susceptibility of the different strains to a primary infection there were marked differences in their ability to develop resistance to infection following repeated exposure to infective larvae. The strains of mice which developed the best resistance also expelled adult worms arising from the previous infections. The adult worms resulting from a primary infection were slowly eliminated in two inbred strains studied whereas no loss occurred from outbred LACA mice. Although males and females of two strains, C3H/HeJ and CBA/H were equally susceptible to a primary infection, the females developed better resistance than the male mice following two oral administrations of third stage larvae. Infected mice of every strain and both sexes contained high levels of IgG1 in the serum.

Animals↗
PubMed1979

Protection of mice against Giardia muris infection.

Strains of mice showing relatively rapid (BALB/c) and defective (C3H/He) spontaneous elimination of Giardia muris displayed marked differences in the degree of resistance to infection induced by prior injection of trophozoites in Freund complete adjuvant.

Animals↗
PubMed1979

Allergenicity of concanavalin A in mice.

Concanavalin A (Con A) is a potent allergen in certain strains of mice and in particularly the H-2Kk mice, A/J, CBA/H, and C3H/He. Using a dose of 100 microgram, the subcutaneous route of injection was the most effective means of inducing high, persistent titers of T cell-dependent circulating anti-Con A reagins without the addition of the classical IgE adjuvants, aluminium hydroxide and Bordetella pertussis vaccine. Haptenated Con A induced reagins with antihapten specificity. In the discussion, one possible contributing factor in Con A allergenicity in genetically responder strains of mice is emphasised, namely, persistence in subcutaneous injection sites.

Administration, Intranasal↗
PubMed1979

Peritoneal cell population of mice infected with Mesocestoides corti as a source of eosinophils.

A prominent feature of the inflammatory cellular response in the peritoneal cavity of Mesocestoides corti-infected mice is a marked and sustained increase in the number of eosinophils. In intact mice, the total number of nucleated cells in the peritoneal cavity rises from less than 5 X 10(6) to more than 50 X 10(6) and, at certain time points, in excess of 50% of these cells are eosinophils. Peritoneal eosinophils are absent in infected hypothymic nude (nu/nu) mice of three genotypes, and eosinophils counts can be elevated in infected nude mice by injection of peripheral lymphoid cells or thymocytes. The peritoneal cells of M. corti-infected mice are a convenient starting cell population for eosinophil purification.

Animals↗
PubMed1979

Plasmodium-infected blood cells analyzed and sorted by flow fluorimetry with the deoxyribonucleic acid binding dye 33258 Hoechst.

Red cells from Plasmodium berghei infected mouse blood can be sorted on the basis of their DNA content with the bisbenzimidazole dye 33258 Hoechst. The optimal conditions for dye uptake have been established and with these conditions uninfected cells are nonfluorescent and can be completely separated from infected cells which exhibit fluorescence in almost direct proportion to the number of parasite nuclei (i.e. DNA) they contain. The number of fluorescent cells detected and their fluorescence intensity is shown to be dependent on the dye concentration and the incubation medium being used. At least a proportion of the infected cells sorted from each fluorescence peak in the cell distribution retain their infectivity in vivo with some, but not all, conditions of labeling. This technique is being used to separate minor cell populations from infected blood for biochemical and immunochemical analyses and to screen human samples for malaria infected cells.

Animals↗
PubMed1979

Short term in vitro cultivation of malaria parasites in Papua New Guinea for preparation of biosynthetically-labelled parasite antigens.

Short term in vitro cultivation has been used successfully for biosynthetic labelling of TCA precipitable macromolecules of Papua New guinean isolates of Plasmodium falciparum. Conditions satisfactory for completion of the asexual erythrocytic cycle were achieved with aa minimum of sophisticated equipment. The techniques used are described in detail and mention is made of possible applications to assessment of chloroquine resistance and the mode of action of inhibitory antisera.

Antigens↗