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Biomedical subjects

A Lanzavecchia

Publications and source records attributed to A Lanzavecchia.

At least 163 records · Page 9Linked to original sources
PubMed1985

Isolation and characterization of Ni-specific T cell clones from patients with Ni-contact dermatitis.

Ni-specific T lymphocyte clones (TLC) were isolated from two patients with Ni-contact dermatitis. All of the isolated TLC required both histocompatible antigen-presenting cells (APC) and Ni for induction of proliferation. By using a panel of HLA-typed Epstein Barr virus-transformed B cells (EBV-B cells) as APC and monoclonal anti-DR antibody, the clones were shown to recognize Ni in the context of HLA class II determinants. All of the clones that were isolated are OKT3+, OKT4+, OKT8-. In the presence of Ni, they polyclonally activate autologous B cells, and in the presence of Ni and autologous EBV-B cells, they produce IL 2 and very high levels of IFN-gamma. The Ni-specific clones should be helpful in the identification of the Ni-induced antigen which is recognized by T cells.

Antigen-Presenting Cells↗
PubMed1985

Specific B lymphocytes efficiently pick up, process and present antigen to T cells.

To study the nature of the antigen bridge between specific B and T lymphocytes we have isolated from the same donor clones of human T cells and EBV-transformed B cells specific for tetanus toxoid (TT). We found that TT-specific B cells are extremely efficient in presenting TT (but not an unrelated antigen) to T cells, as they can trigger T cell proliferation in the presence of only 10(-12) M TT, a concentration that is approximately 10(4) times lower than that required for presentation by conventional antigen-presenting cells such as macrophages or non-specific B cells. The high avidity of the interaction between specific B and T cells is reflected by the resistance to inhibition by antibodies against the T4 antigen. Experiments with fixed and chloroquine-treated B cells show that the role of surface antibodies is limited to the uptake of antigen and that in order to obtain presentation, the antigen has to be internalized, processed and subsequently displayed on the cell surface, where it becomes available for T cell recognition in an MHC-restricted fashion.

Antigen-Presenting Cells↗
PubMed1984

The same human alloreactive T cell clone can help both B lymphocytes and specific cytotoxic precursors.

Human alloreactive proliferating T cell clones have been compared for their capacity to provide help for B cell activation and the generation of a specific cytotoxic response. The results demonstrate that, when triggered by the relevant alloantigen, the same T cell clone can induce a strong polyclonal B cell activation and serve as the only source of helper cells for the generation of a specific cytotoxic response by any source of CTL precursors against any stimulator cell present in culture.

B-Lymphocytes↗
PubMed1984

In vitro stimulation of IgE production at a single precursor level by human alloreactive T helper clones.

Human alloreactive proliferating T cell clones were isolated by a combination of allogeneic stimulation and interleukin 2-dependent growth. When cultured with B cells and macrophages bearing the appropriate alloantigens, the helper clones induced the production of high levels of IgE, while in the absence of the appropriate stimulation B cells produced undetectable IgE levels. Allogeneic peripheral blood T cells did not provide any help, but rather suppressed the IgE production induced by the alloreactive clones. The development of culture conditions where the help provided by specific T cell clones is non-limiting and suppressor-cytotoxic T cells are absent allowed the set up of limiting dilution experiments to determine the frequency of the B cells activated to high rate IgE production. One in 2,200-6,000 B cells in the peripheral blood of normal donors was activated to produce measurable amounts of IgE. This experimental system will allow the clonal analysis of the IgE antibody repertoire, in different physiological and pathological conditions.

B-Lymphocytes↗
PubMed1983

Activation of human B lymphocytes: frequency of antigen-specific B cells triggered by alloreactive or by antigen-specific T cell clones.

Human T cell clones specific for tetanus toxoid (TT) or for alloantigens were isolated and expanded in culture using antigen stimulation and soluble growth factors. When stimulated by the specific antigen, the clones were able to proliferate in the absence of exogenous growth factors and to provide help to B cells. The alloreactive and TT-specific clones were compared for their capacity to help an anti-TT as well as a polyclonal antibody response. The frequency of the B cells activated to the production of specific antibody was determined by limiting dilution analysis in cultures containing limiting numbers of responding B cells and optimal numbers of cloned T helper cells. In these conditions a single activated b cell was able to produce about 10 ng of antibody. TT-specific clones, in the presence of low TT concentrations, selectively induced a number of TT-specific B cells to produce IgG antibody in the absence of a detectable polyclonal B cell activation. On the other hand the alloreactive clones activated higher numbers of TT-specific B cells as a part of a strong polyspecific B cell activation. In this case the antibody production did not require the presence of TT in culture; furthermore cells producing antibodies of unrelated specificities were also activated in allostimulated cultures. IgG anti-TT were produced only by immune donors, while IgM anti-TT were produced by immune and nonimmune donors, providing the B cells were activated by alloreactive clones. These data demonstrate that human memory B cells can be triggered by both antigen-specific and alloreactive T cells to antibody production. The alloreactive clones can therefore be used to analyze at the clonal level the repertoire of a pool of B cells that contain most, if not all, the memory antibody specificities.

Antibody Formation↗
PubMed1983

One out of five peripheral blood B lymphocytes is activated to high-rate Ig production by human alloreactive T cell clones.

Human alloreactive helper T cell clones were isolated from a secondary mixed lymphocyte reaction by limiting dilution in the presence of irradiated stimulator cells and T cell growth factor (interleukin 2). When cultured with B cells and macrophages possessing the relevant alloantigens, the T cell clones proliferated and induced a strong B cell activation with production of high immunoglobulin levels. Limiting dilution of the B cells from the peripheral blood showed that about one in 5-10 can be activated to produce IgG, one in 10 IgM, one in 20-40 IgA and one in 2000-5000 IgE. Following stimulation by the relevant alloantigen, the clones were able to help also B cells that lacked the alloantigen, indicating that a direct T-B cell interaction is not required. This method is particularly interesting because it is suitable for the clonal analysis of a B cell subset that is triggered in the absence of antigen by an unrestricted T cell help.

Antibody-Producing Cells↗
PubMed1983

In vitro selective expansion of allergen specific T cells from atopic patients.

Peripheral blood mononuclear cells from atopic donors were stimulated in vitro with allergens (Rye group I or Dermatophagoides pteronyssinus). T cell lines were originated and maintained in long term culture using IL-2 and periodical restimulations with allergen. The lines were antigen specific (i.e. responded to the allergen used to raise them and not to other antigens) and required that the antigen was presented by autologous cells (i.e. they were restricted). The restriction elements were probably at the level of HLA-DR antigens since the proliferative response was specifically blocked by anti-HLA-DR antibodies. Surface marker analysis revealed that the lines comprised mainly cells with an helper/inducer phenotype, although cells with markers of the suppressor/cytotoxic T cells were also present. The lines could be cloned by limiting dilution and clones with the same restriction and specificity as the parental line were isolated. These studies demonstrate the possibility of obtaining a large number of allergen specific human T cells that can be used for further in vitro studies on the regulation of the IgE response.

Allergens↗
PubMed1982

Human T cell lines with antigen specificity and helper activity.

Human T blasts, obtained by stimulation of peripheral blood mononuclear cells (PBM) with tetanus toxoid, diphtheria toxoid or Candida albicans, were expanded in long-term culture using alternate periods of antigen restimulation and growth in media containing interleukin 2. The cells gave a proliferative response only to the antigen originally used for stimulation. Such as response was strictly dependent upon the presence of autologous but not of allogeneic mitomycin C-treated mononuclear cells. When added to autologous PBM depleted of E-rosetting cells together with the specific antigen, the T blasts induced a polyclonal proliferation and differentiation of B cells. Allogeneic B cells were activated by antigen-stimulated T blasts only in the presence of irradiated mononuclear cells autologous to the responding T blasts. The above responses seemed not to be regulated solely by the release of soluble factors; apparently cell to cell interactions had to take place to obtain an efficient B cell activation.

Antibody-Producing Cells↗
PubMed1980

Activation of human peripheral blood lymphocytes: effect of concanavalin A and lipopolysaccharide on in vitro synthesis of DNA and immunoglobulins.

We studied the interaction of lipopolysaccharide (LPS) and concanavalin A (Con A) with regard to IgM and IgG production in in vitro cultures of human peripheral blood lymphocytes (PBL). In our system LPS alone over a wide range of concentrations did not stimulate detectable IgM or IgG production, while Con A at optimal (6 microgram/ml) and suboptimal (0.6 microgram/ml) mitogenic concentrations induced synthesis of small amounts of Ig. A marked enhancing effect was present when both Con A and LPS were added to the cultures. The different doses of LPS has similar effects on both classes of Ig, and typical dose-response curves were obtained. To evaluate the cellular basis of this synergism, the effect on cell proliferation was studied under identical experimental conditions in normal subjects and patients with X-linked agammaglobulinaemia (X-LA). Parallel cultures were set up after monocyte depletion by adherence on Petri dishes. On day 3, increasing doses of LPS were associated with progressive decreases in 3H-thymidine (3H-TdR) incorporation. Similar results were obtained with normal lymphocytes and those from X-LA patients. Monocyte depletion did not substantially alter the lymphocyte response pattern. The preferential induction of helper activities, either directly by helper stimulation or indirectly by suppressor inhibition, is suggested as a possible mechanism of the interaction observed.

Agammaglobulinemia↗
PubMed1980

Ontogeny of secretory immunity: levels of secretory IgA and natural antibodies in saliva.

In 187 healthy subjects from 2 months to 27 years of age, secretory IgA and free secretory component were assayed in samples of whole saliva obtained before and after stimulation with lemon juice. Antibody titers against Escherichia coli O antigens and against rabbit erythrocytes were also dosed in unstimulated saliva. Secretory IgA, undetectable in newborns, was present in all 2-month-olds tested in both unstimulated and stimulated saliva; thereafter secretory IgA levels increased progressively, reaching adult values by 6 to 8 years in unstimulated saliva and already by 2 to 4 years in stimulated saliva. The antibody titers assessed in unstimulated saliva followed a similar pattern also reaching adult values by 6 to 8 years. On the other hand, free secretory component levels showed no significant variation with age in unstimulated saliva whereas a slight increase was observed in the first year of life in stimulated saliva.

Adolescent↗
PubMed1980

Concanavalin A induces a T-cell dependent activation of human tonsil B cells in vitro.

Tonsillar lymphocytes cultured for 7 days in serum-supplemented RPMI-1640 medium were stimulated with Con A or PWM. IgM production was assessed by a hemagglutination inhibition assay. IgM was produced after Con A as well as PWM stimulation. Our data show that T-cell irradiation and/or addition of small numbers of T cells to the responding B-cell population facilitate(s) IgM synthesis. In particular in Con A-stimulated cultures the T-cell number is critical in regulating the appearance of suppressor effects. The results are discussed in terms of the various subpopulations possibly involved in the response to these mitogens.

B-Lymphocytes↗
PubMed1979

Effect of in vitro treatment with reducing drugs on structure and function of human secretory immunoglobulin A.

Samples of unstimulated whole saliva from 15 healthy children with 0.5--6 mg/100 ml of secretory IgA and from 10 healthy adults with 4--18 mg/100 ml of secretory IgA were pooled and treated in vitro with dithiothreitol and alpha-mercaptopropionylglycine. The effect of these reducing drugs on the immunochemical properties of secretory IgA was evaluated. Dithiothreitol induced depolymerization of secretory IgA and splitting of the secretory piece from the IgA molecule; furthermore it strongly reduced the titer of secretory antibodies to Escherichia coli antigens. The drug alpha-mercaptopropionylglycine apparently did not affect either the polymeric structure of secretory IgA or the titer of secretory anti-E. coli antibodies; however it induced splitting of the secretory piece. On the whole it appers that drugs with reducing properties, currently employed for liquifying mucous secretions in clinical practice, should be carefully evaluated for possible depressive side-effects on local immunity.

Adult↗
PubMed1979

Plaque assay with protein A-coated erythrocytes for the evaluation of human immunoglobulin-secreting cells induced by pokeweed mitogen.

Cells secreting IgM, IgG and IgA were evaluated in cultures of human peripheral blood lymphocytes stimulated in vitro with pokeweed mitogen by a haemolytic plaque assay using protein A-coated erythrocytes in the presence of class-specific antisera. Kinetic study revealed that immunoglobulin-secreting cells appeared after 3 days of culture and peaked between days 5 and 7. IgM-secreting cells predominated throughout the culture period. This plaque assay is a useful and sensitive in vitro test for the evaluation of polyclonal B-cell activation in humans and may provide a good approach to the study of disturbances in the synthesis of the various classes of immunoglobulins.

Adult↗
PubMed1978

Polyclonal activation of human B lymphocytes in vitro by pokeweed mitogen: a simple technique for the simultaneous assessment of cell proliferation, generation of plasma cells, plaque-forming cells and immunoglobulin production.

A simple technique has been worked out for the simultaneous assessment of cell proliferation, generation of plasma cells, plaque-forming cells and immunoglobulin production from single cultures of 1 X 10(6) human peripheral blood lymphocytes stimulated with pokeweed mitogen (PWM). Kinetic studies showed that number of cells, thymidine incorporation rate, number of plaque-forming cells against fluorescein-isothiocyanate-haptenated sheep erythrocytes and concentration of IgM and IgG in the supernatant peaked on the average between day 5 and 7 of culture. This technique is particularly suitable for the analysis of hypogammaglobulinaemias in infancy.

Adult↗
PubMed1978

Immunodeficiency in Down's syndrome. Titres of "natural" antibodies to E. coli and rabbit erythrocytes at different ages.

"Natural" antibody titres to E. coli O antigens of different serotypes and to rabbit red blood cells were determined in 86 subjects with Down's syndrome and 79 mentally retarded but chromosomally normal controls ranging in age from 10 months to 52 years. Subjects in the two groups were matched for sex, age and socio-environmental conditions. Titres of both antibodies, assessed by haemagglutination, were significantly lower in subjects with DS in the 1 to 5 year old group. E. coli antibodies transiently increased to normal values in subjects with DS during the second 5 years of life, thereafter rapidly declining to levels significantly lower than those observed in controls. The titres of antibodies to rabbit erythrocytes in subjects with Down's syndrome showed a more variable course transiently approaching normal values in the 7-10 year group and after 20 years of age. These data are interpreted as further evidence for the existence of a congenital immunodeficiency in Down's syndrome.

Adolescent↗
PubMed1978

Immunodeficiency in Down's syndrome: T-lymphocyte subset imbalance in trisomic children.

In fourteen children with Down's syndrome the percentage of circulating T-cells forming rosettes with sheep erythrocytes, either in the presence or in the absence of foetal calf serum, was significantly lower than in appropriately matched controls. In contrast the percentage of T-cells forming rosettes with human erythrocytes was significantly higher in children with Down's syndrome than in controls. These data support the hypothesis that a defective T-cell maturation is an early integral feature of Down's syndrome.

Child, Preschool↗
PubMed1977

Human T lymphocyte subset identification according to avidity for sheep erythrocytes and rosetting capacity with allogeneic red blood cells.

Peripheral blood T lymphocytes of healthy adults were separated in appropriate Ficoll-Hypaque mixtures according to their avidity for sheep red blood cells (SRBC) and re-rosetted with both SRBC and human red blood cells (HRBC). The results showed that separation procedures causing relative depletion of lymphocytes with high avidity for SRBC led to a parallel increase in the percentage of cells forming rosettes with HRBC. Separation procedures leading to almost complete depletion of cells forming rosettes with SRBC also almost completely eliminated cells forming rosettes with HRBC. The overall data suggest that circulating T cells of healthy adults can be divided into two subsets according to their avidity for SRBC. T lymphocytes with low avidity for SRBC preferentially express receptors for HRBC. These data are presented as further evidence of T lymphocyte heterogeneity.

Animals↗