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L B Lundin

Publications and source records attributed to L B Lundin.

11 recordsLinked to original sources
PubMed1981

Proliferation and lymphocyte stimulatory capacity of Theileria-infected lymphoblastoid cells before and after the elimination of intracellular parasites.

A prominent pathogenic facet of Theileria infections is that the parasite infects lymphocytes and 'transforms' them into parasitized lymphoblastoid cells which are highly proliferative and can be cultured indefinitely in vitro. To analyse the relationship between the intracellular parasite and lymphocyte transformation we have studied the effects of eliminating parasites from these lymphoblastoid cells using the naphthoquinone derivative 993.C. Treatment of Theileria-infected lymphoblastoid cells with 993.C gradually eliminates intracellular parasites but cell proliferation is not inhibited until several days after parasite elimination. The proliferating cells no longer contain schizont particles and are medium-sized lymphocytes and small blast cells. The surface phenotype of these cells, as defined by lectins and monoclonal antibodies, remains unchanged after parasite elimination. The division of non-parasitized cells, under the culture conditions examined, was not indefinite. The compound 993.C itself does not appear to be mitogenic and possible mechanisms for this continued division are discussed. It has been previously reported that co-cultivation of irradiated Theileria-infected lymphoblastoid cells with autologous lymphocytes induces marked DNA synthesis in the latter. We examined further the relevance of this observation for immunity to Theileria by using lymphoblastoid cells treated with 993.C. Elimination of intracellular parasites by this compound does not impair the ability of these cells to stimulate DNA synthesis in autologous lymphocytes. Furthermore, lymphocytes from Theileria-immune or non-immune cattle react similarly. The reaction differs from a classical mixed lymphocyte reaction induced by antigens encoded in the main histocompatibility complex since the stimulator cells are exclusively T lymphocyte-derived cells, the magnitude of response is greater and stimulated lymphocytes are able to act as 'stimulator cells' to fresh autologous lymphocytes. Thus we question the immunological relevance of the observed lymphocyte division. The possibility that Theileria-infected lymphoblastoid cells carry viral genomes or infectious virus particles is discussed. Preliminary electron microscopic studies have not revealed any virus particles.

Animals↗
PubMed1981

Trypanosome variable surface antigens: studies using two-dimensional gel electrophoresis and monoclonal antibodies.

Variable surface antigens of cloned populations of African trypanosomes were studied using 2-dimensional gel electrophoresis and monoclonal antibodies. Two-dimensional gel maps showed that the only major differences in protein profiles of the non-nuclear materials from different clones of solubilized trypanosomes were attributable to the variable surface antigens and that purification doesn't alter these molecules, at least with respect to charge and apparent m.w. Purified variable surface antigens were used as immunogens and a number of monoclonal antibodies were derived using cell-fusion technology. In radioimmunoassay, each of the monoclonal reagents was shown to be specific for the immunizing antigen, and in immunofluorescence tests using acetone-fixed trypanosomes, each bound specifically to the clone from which the antigens were purified. Only 20% of the monoclonal reagents bound to living trypanosomes, however, providing evidence for both exposed and nonexposed antigenic sites on the variable surface antigens. Those reagents derived to a single antigen bound to different nonoverlapping antigenic sites, which were on the protein portion of the molecules and not the carbohydrate moieties. The data show that monoclonal antibodies are ideal probes for studying localization of antigenic sites on the antigen molecules and for studying antigen synthesis, glycosylation, and architecture in relation to the cell surface. In addition, the finding of exposed and nonexposed antigenic sites on trypanosome variable antigens allows a possible explanation for the role of the antigens in pathogenesis of African trypanosomiasis.

Animals↗
PubMed1980

Methods for derivation and detection of anti-parasite monoclonal antibodies.

We describe detailed methods for derivation and cloning of myeloma hybrids which secrete antibodies specific for antigens of protozoan parasites. The methods were designed to enable the derivation of large numbers of specific monoclonal antibodies and to give high cloning efficiencies of desired hybrids. Although special attention is paid to derivation and detection of anti-parasite antibodies, the methods can be applied to many different antibody-antigen systems. Using the described methods we have isolated more than 90 myeloma hybrids which secrete antibodies specific for antigens of African trypanosomes and Theileria parasites, thus illustrating their effectiveness.

Animals↗
PubMed1979

Cell-mediated immunity to Theileria-transformed cell lines.

In East and Central Africa the protozoan parasite Theileria parva causes a disease of cattle called East Coast fever (ECF). In Kenya alone between 60,000 and 85,000 cattle die from ECF every year. Infected animals can recover from ECF either naturally or after treatment with tetracyclines or menoctone and are subsequently able to resist challenge with the homologous strain of parasite. That this acquired resistance is due to cell-mediated rather than humoral immunity has been suspected but never decisively shown. A major difficulty in studying immunity to ECF has been the lack of inbred animals for studying Theileria-specific immunity in the absence of allogeneic histocompatibility barriers. We have avoided this problem by measuring cell-mediated immune responses in a syngeneic system in vitro. Unidirectional mixed lymphocyte cultures (MLC) were set up using bovine peripheral blood lymphocytes (PBL) as responder cells and autologous cell lines transformed in vitro by T. parva as stimulator cells. In these cultures, DNA synthesis was induced in PBL from both normal and Theileria-immune animals. However, cytotoxic lymphocytes were induced only in cultures containing responder lymphocytes from Theileria-immune cattle. The results show that Theileria-transformed cells express antigens which are recognized by effector cells and provide evidence that cell-mediated cytotoxic mechanisms function in immunity to ECF.

Animals↗
PubMed1979

Immune depression in trypanosome-infected mice. II. Characterization of the spleen cell types involved.

Spleen cells from Trypanosoma congolense-infected mice showed a drastic depression in their capacity to respond to B and T lymphocyte mitogens and to allogeneic spleen cells in mixed lymphocyte cultures. Spleen cells from infected mice were also poor stimulators in mixed lymphocyte cultures. The poor responsiveness or stimulation capacity was not due simply to dilution of relevant B or T lymphocytes by the large number of null cells found in the spleens of infected animals. These null cells expressed approximately eight times more H-2 antigen than spleen cells from normal (uninfected) mice and were devoid of Ia antigens.

Animals↗
PubMed1979

Immune depression in trypanosome-infected mice. III. suppressor cells.

Spleen cells from trypanosome-infected mice strongly suppressed lymphocyte stimulation induced in normal spleen cell populations by lipopolysaccharide, concanavalin A or allogeneic (H-2-different) stimulator cells. This suppression was not H-2-restricted, as responses of spleen lymphocytes both allogeneic and syngeneic to the suppressors were inhibited. Irradiation or mitomycin C treatment of suppressor populations markedly reduced but did not eliminate suppressor activity. Suppressor populations were effective when present in very low numbers. Addition of suppressor cells to mixed lymphocyte cultures at various intervals after initiation of the cultures showed that the suppressors require 48 h to manifest their activity. Cell depletion or enrichment experiments indicate that the mechanism of suppression is complex and involves more than one cell type.

Animals↗
PubMed1979

Suppressor cells in Trypanosoma congolense-infected mice.

Spleen cells from mice infected with T. congolense strongly suppressed lymphocyte stimulation induced in normal spleen cells by incubation with mitogens or allogeneic cells. Cell dilution studies showed that suppressor activity was extremely strong. Suppressor cell activity was markedly reduced by treatment of spleen cell populations with mitomycin-C and was unaffected by treatment with anti-Thy.1 sera and complement. Removal of cells which bound carbonyl iron or which bound to nylon columns, decreased but did not abolish suppressor activity.

Animals↗
PubMed1979

The bovine lymphoid system: binding and stimulation of peripheral blood lymphocytes by lectins.

We tested ability of 11 different lectins to stimulate DNA synthesis in bovine peripheral blood lymphocytes, using a wide range of experimental conditions. Five of the 6 lectins which induced DNA synthesis (concanavalin A, succinyl-concanavalin A, phytohemagglutinin M, pokeweed mitogens and lipopolysaccharide) did so under conditions similar to those optimal for stimulation of murine lymphocytes. The other lectin (peanut agglutinin) stimulated normal bovine lymphocytes whereas it does not stimulate normal mouse, rat, guinea pig or human lymphocytes. The binding of 5 different lectins to bovine peripheral blood lymphocytes was measured by fluorescence microscopy. Four of the lectins bound to various proportions of cells. Double labeling experiments using a rhodamine-labeled goat anti-bovine immunoglobulin reagent and fluorescein-labeled lectins showed that both peanut agglutinin and soybean agglutinin bound to lymphocyte populations which were negative for surface immunoglobulin. The majority of lymphocytes negative for surface immunoglobulin bound peanut agglutinin, indicating that this lectin may bind specifically to bovine 'T' lymphocytes.

Animals↗
PubMed1979

Immune depression in trypanosome-infected mice. IV. Kinetics of suppression and alleviation by the trypanocidal drug Berenil.

Mice infected with T. congolense were monitored for numbers of parasites in peripheral blood, changes in spleen cell populations, immune depression and suppressor cell activity. Depression of B and T lymphocyte responses and the appearance of suppressor cell activity in spleens of infected mice paralleled the appearance of parasites in the peripheral blood. The immune depression was manifest before any visible changes in spleen cell populations occurred. Treatment of infected mice with the trypanocidal drug Berenil resulted in a rapid clearance of parasites from the peripheral blood, a parallel loss of immune depression and suppressor cell activity and a gradual return towards normal spleen cell composition. The splenic white pulp showed severe depletion following longstanding infection with T. congolense. However, following treatment with Berenil there was rapid repopulation of the white pulp and widespread active germinal centre formation.

Amidines↗
PubMed1978

Immune depression in trypanosome-infected mice. I. Depressed T lymphocyte responses.

Using a wide range of experimental conditions, several kinds of T lymphocyte responses in spleen cell populations from trypanosome-infected mice were studied. Lymphocyte stimulation after culture with the mitogen concanavalin A or with histoincompatible cells differing at H-2 or minor lymphocyte-stimulating loci was reduced or abolished in spleen cells from infected mice when compared with responses of spleen cells from uninfected controls. In addition, cytotoxic lymphocytes were not generated in mixed lymphocyte cultures which contained spleen cells from infected animals. Allogeneic skin grafting experiments performed with normal and infected mice showed that a decreased T lymphocyte response also occurs in vivo. The depressed immune responses were not simply due to low numbers of T lymphocytes in spleens of infected animals, but reflected a generalized immune depression which was not antigen-specific.

Animals↗