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I Motta

Publications and source records attributed to I Motta.

At least 19 recordsLinked to original sources
PubMed2001

Cross-presentation by dendritic cells of tumor antigen expressed in apoptotic recombinant canarypox virus-infected dendritic cells.

We have investigated the possible usefulness of recombinant canarypox virus (ALVAC) encoding the melanoma-associated Ag, Melan-A/MART-1 (MART-1), in cancer immunotherapy, using a dendritic cell (DC)-based approach. ALVAC MART-1-infected DC express, and are able to process and present, the Ag coded by the viral vector. One consistent feature of infection by ALVAC is that these viruses induce apoptosis, and we show cross-presentation of Ag when uninfected DC are cocultured with ALVAC MART-1-infected DC. Uptake of apoptotic virally infected DC by uninfected DC and subsequent expression of tumor Ag in the latter were verified by flow cytometry analysis, image cytometry, and confocal microscopy. Functional activity was monitored in vitro by the stimulation of a MART-1-specific cytotoxic T cell clone. Heightened efficiency in Ag presentation is evidenced in the 2- to 3-fold increase in IFN-gamma production by the T cell clone, as compared with the ALVAC-infected DC alone. Cocultures of ALVAC MART-1-infected and uninfected DC are able to induce MART-1-specific T cell immune responses, as assessed by HLA class I/peptide tetramer binding, IFN-gamma ELISPOT assays, and cytotoxicity tests. Overall, our data indicate that DC infected with recombinant canarypox viruses may represent an efficient presentation platform for tumor Ags, which can be exploited in clinical studies.

Antigen Presentation↗
PubMed1998

In vitro induction of naive cytotoxic T lymphocytes with complexes of peptide and recombinant MHC class I molecules coated onto beads: role of TCR/ligand density.

We previously reported that complexes of peptide with soluble single-chain recombinant MHC (SC-MHC) class I molecules are able to induce cytotoxic T lymphocytes (CTL) in vitro in a murine system with an efficiency comparable to that observed with peptide-pulsed dendritic cells as antigen-presenting cells. In this report, we have assessed the capacity of preformed peptide/SC-Kd complexes in monomeric or dimeric form as well as of peptide/SC-Kd-loaded beads to generate in vitro specific CTL responses from naive DBA/2 spleen cells. Peptide/SC-Kd-coated beads were consistently more efficient. We evaluated the role of costimulatory molecules, using monoclonal antibodies anti-CD80 or anti-CD86. In addition, the capacity of peptide/SC-Kd-coated beads to generate a CTL response from purified naive CD8+ T cells was ascertained. Taken together, the results indicate that, under our conditions, CTL priming does not require the participation of co-stimulatory molecules and is the consequence of a direct interaction between the cognate TCR on peptide-specific CTL precursors and the peptide/SC-Kd-loaded beads. Titration of the amount of preformed complexes of SC-Kd and peptide 170-179 of HLA-CW3 that need to be coated onto the beads to prime CTL precursors shows an activation threshold which can be calculated to be between 25000 and 50000 complexes. In effect, in cultures stimulated with specific peptide CW3/SC-Kd complexes representing less than 50% occupancy of the total (10(5)) complexes on the beads, no peptide-specific cytolytic activity was observed. These results suggest that the efficiency of the primary CTL induction depends on the density of specific peptide/SC-Kd complexes present on the beads.

Animals↗
PubMed1998

In vitro induction of specific cytotoxic T lymphocytes using recombinant single-chain MHC class I/peptide complexes.

We have previously described the production and purification of a murine single-chain, soluble recombinant major histocompatibility complex (MHC) class I molecule (SC-Kd). A similar strategy was devised to produce a recombinant HLA-A2.1 (SC-A2) molecule. The latter was composed of the first three domains of the HLA-A2.1 heavy chain connected to human beta 2-microglobulin through a spacer of 15 amino acids. Immunoaffinity-purified SC-A2 molecules-were correctly folded and biologically functional. They specifically bound HLA-A2-restricted peptides and induced a peptide-specific cytotoxic T lymphocyte (CTL) clone to proliferate and secrete interleukin-2. The ability of murine and human SC-MHC molecules to elicit primary CTLs in vitro was next investigated. When coated in high density onto beads, complexes of antigenic peptide and SC-Kd or SC-A2 molecules efficiently induced a specific primary CTL response in vitro. Furthermore, the structural features of these CTLs were characterized by T cell receptor-beta chain analysis, which revealed rearrangements very similar, if not identical, to those found in CTLs generated by in vivo immunization. Such single-chain, soluble recombinant MHC class I molecules should provide a useful tool in particular for peptide binding assays and for in vitro primary CTL induction to identify immunogenic peptides such as those derived from known tumor-associated antigens.

Animals↗
PubMed1995

Interleukin-2 down-modulates memory T helper lymphocyte development during antigenic stimulation in vitro.

Using an in vitro antigenic stimulation model of murine spleen cells in the presence of the immunosuppressor cyclosporin A (CSA) we have previously reported that not only does this drug not interfere with the differentiation of T lymphocytes into memory cells it appears to favor this differentiation (Motta, I. et al., Eur. J. Immunol. 1991. 21:551). Because CSA blocks interleukin-2 (IL-2) gene expression, we have analyzed the effect of this cytokine on memory T helper cell development. Murine splenic cells were primed for 6 days with sheep red blood cells (SRBC) in protocols in which either IL-2 was not produced or its biological activity was neutralized by anti-IL-2 receptor (R) antibodies. The helper function of the recovered T cells was revealed by their capacity to help virgin B splenocytes produce anti-SRBC antibodies upon challenge in vitro. We found that CD4+ cells primed in the absence of IL-2, provoked either by IL-2 gene transcription blockade by CSA or by treatment with anti-IL-2R antibodies, afford the best helper functions. These cells exhibit a memory-type phenotype characterized by the low expression of the MEL-14 marker and the high expression of the CD44 marker. Evidence is also presented that memory T helper cells originate in part from naive subset displaying the MEL-14hi phenotype. The pattern of expression of the genes encoding different cytokines (IL-2, IL-4, IL-5 and interferon-gamma) following a secondary antigenic stimulation shows that the helper function of the cells primed in the absence of IL-2 correlates with the up-regulation of the IL-2 and the IL-5 genes. From these data, we conclude that IL-2 plays a major role in the control of memory T helper cell induction.

Animals↗
PubMed1991

Interleukin 2/interleukin 4-independent T helper cell generation during an in vitro antigenic stimulation of mouse spleen cells in the presence of cyclosporin A.

Cyclosporin A (CsA), an immunosuppressive drug which completely suppresses the humoral response to thymus-dependent antigens, does not affect the generation of T helper (Th) cells during an in vitro stimulation of murine spleen cells with sheep red blood cells. The appearance of Th cells depends on time and their development can be prevented by X-ray irradiation performed at the onset of the culture and up to 3-4 days later; however, beyond this time, irradiation is ineffective, suggesting that cell proliferation is essentially completed by this time. The activity of Th cells generated in the presence of CsA is resistant to irradiation, indicating that the effector cells belong to a memory subset. Limiting dilution analysis has shown that the frequency of the Th cells recovered from 6-day sheep red blood cell-stimulated and CsA-treated cultures is of approximately 1.4 X 10(-3), representing an increment of about 500-fold compared to naive spleen cells. The increased frequency of Th cells and the sensitivity to irradiation of the generation of these cells demonstrate that Th cell precursors proliferate in the presence of CsA. Lymphokine genes transcription analysis confirms that the inhibition of interleukin (IL) 2/IL 4 gene expression is one target of CsA action. That the generation of Th memory cells can nevertheless take place strongly argues in favor of the existence of an IL 2/IL 4-independent pathway for murine T cell proliferation. Our finding that the transcription of the IL 7 gene is not inhibited by CsA raises the possibility for a role of this T cell growth factor in the generation of memory Th cells.

Animals↗
PubMed1987

Cyclosporin A does not affect the in vitro induction of antigen-specific delayed-type hypersensitivity-mediating T cells.

The effect of cyclosporin A (CsA) on the in vitro induction of sheep red blood cell (SRBC)-specific T cells mediating the delayed-type hypersensitivity (DTH) reaction was studied. CsA (1 microgram/ml) addition to the culture medium totally inhibits the in vitro anti-SRBC humoral response but does not interfere with the generation of anti-SRBC DTH-mediating T (TDTH) cells. The induction of TDTH requires the presence of antigen and their expression is mediated selectively by the antigen used in the culture. The TDTH cells generated are Lyt-1+,2- and their induction occurs with a similar efficiency in CsA-treated and untreated cultures: the frequency of the TDTH cells increases by a factor of 10 to 20 during the 6-day incubation period. Lyt-2+ suppressor cells are also generated in CsA-treated or untreated cultures. Our results suggest that a small fraction of T cells can be driven into the proliferative pathway by antigen even in presence of CsA.

Animals↗
PubMed1986

Effect(s) of lipopolysaccharide on lectin-induced T-cell activation.

The present study focuses on the effect of lipopolysaccharide (LPS) on the cellular events leading to T-cell activation by concanavalin A (Con A). Interleukin 2 (Il-2) production is much reduced in Con A-stimulated cultures of spleen cells derived from LPS-treated mice. This depressed Il-2 synthesis is not related to the eventual activity of LPS-activated suppressive B cells. Rather, it reflects an ineffective collaboration between adherent cells and T lymphocytes. The low level of Il-2 produced by LPS-sensitized spleen cells is sufficient for lectin-induced T-cell proliferation. Moreover, acquisition of responsiveness to Il-2 is unaltered by LPS. No strict correlation was found between the deficiency in Il-2 production and the inability of LPS-sensitized spleen cells to generate a thymus-dependent response. Less time (5 hr) is needed for LPS to exert its inhibitory effect on an anti-sheep red blood cell response than on Il-2 synthesis (at least 24 hr). Results are discussed in terms of cellular interactions implicated in a polyclonal T-cell response and with regard to the contribution of Il-2 to the LPS-induced immune unresponsiveness.

Animals↗
PubMed1985

Effects of suramin on the immune responses to sheep red blood cells in mice. I. In vivo studies.

The effect of Suramin on the cell-mediated delayed-type hypersensitivity (DTH) and the humoral immune responses elicited in mice by sheep erythrocytes was studied. The results show that administration of Suramin, at various times before or after antigenic sensitization, results in a profound inhibition of cell-mediated responses but has no adverse effect on antibody production. Suramin was particularly effective when given during the effector phase of DTH: mice which were treated with this drug, 4 days after immunization, at the time of skin testing, exhibit negative or low DTH responses compared to control mice. Evidence is presented that this short-term Suramin-induced suppressive effect on the expression of DTH is related to a defective recruitment, by sensitized T lymphocytes, of phagocytic cells at the site of the inflammatory reaction. In addition, when treatment with Suramin precedes by 8 days (Day -8) or by 1 hr sensitization with sheep erythrocytes for DTH, decreased DTH reactions over controls were observed. The inhibitory effect exerted by Suramin administered on Day -8 can be reversed by increasing the dose, from 10(6) to 10(8) sheep erythrocytes, of the sensitizing antigen. The possibility is discussed that, in this case, Suramin may interfere with the generation of DTH-mediating cells through a rapid degradation of antigen related to the Suramin-induced hyperplasia of the mononuclear phagocyte system. In contrast, DTH anergy in mice treated with Suramin 1 hr before sensitization is maintained regardless of the sensitizing antigen dose. Analysis of the sensitized lymphocyte population in these mice indicates that Suramin does not prevent the induction of DTH-mediating cells and suggests that the expression of these latter is inhibited by suppressive cells which are generated as a result of drug treatment.

Animals↗
PubMed1985

Effects of suramin on the immune responses to sheep red blood cells in mice. II. In vitro studies.

The effect of Suramin on the secondary in vitro response to sheep erythrocytes (SRBC) was studied. Spleen cells from mice which were treated with Suramin immediately prior to sensitization with SRBC failed to respond to an in vitro SRBC challenge. This Suramin-induced immunosuppression is not related to a defect in macrophage or B-cell function(s). Suramin does not interfere with the induction by SRBC of radioresistant and radiosensitive helper-T-cell subpopulations. Cell separation studies, using wheat germ agglutinin, showed radiosensitive helper-T-cell function in the nonagglutinated fraction while the radioresistant helper activities are carried out by the agglutinated subpopulation. Evidence is presented that Suramin administration results in a suppressive T-cell activity which can be demonstrated in the subpopulation agglutinated by wheat germ agglutinin. The role of such suppressive T cells in the inhibitory effect exerted by Suramin on the cell-mediated delayed-type hypersensitivity response to SRBC is discussed.

Animals↗
PubMed1983

Igh-V or closely linked gene(s) control immunological memory to a thymus-independent antigen.

Mice mount a normal primary antibody response on stimulation with the thymic-independent antigen trinitrophenylated lipopolysaccharide (TNP-LPS). Although we have previously reported the generation of functional B-memory lymphocytes to TNP-LPS, this memory response was only observed in few mouse strains. Here we have used congeneic mouse strains in an attempt to locate the genetic regions involved in the memory response. We show that genes of the major histocompatibility complex (MHC) do not have a critical role but that genes coding for the variable region of immunoglobulin heavy chains or gene(s) closely linked to them are required for memory cell induction by TNP-LPS.

Animals↗
PubMed1983

Effect of cyclosporin A on the induction and activation of B memory cells by thymus-independent antigens in mice.

The effect of cyclosporin A on the induction and activation of B memory cells by thymus-independent (TI) antigens was investigated. Studies were carried out in C57BL/6 mice, a strain in which TI.1 trinitrophenyl-lipopolysaccharide (TNP-LPS) and TI.2 dinitrophenyl-(DNP)-Ficoll antigens can elicit a secondary response. Evidence is presented that cyclosporin A does not adversely affect the primary or secondary response to TNP-LPS. In contrast, this fungal metabolite prevents the triggering of virgin B lymphocytes and TNP-LPS-induced memory cells by DNP-Ficoll. Cyclosporin A does not interfere with the generation of hapten-specific B memory cells by TNP-LPS or DNP-Ficoll. These findings are discussed in terms of B cell lineages leading to antibody-forming cell precursors and memory cells.

Animals↗
PubMed1983

Generation of immune memory by haptenated derivatives of thymus-independent antigens in C57BL/6 mice. I. The differentiation of memory B lymphocytes into antibody-secreting cells depends on the nature of the thymus-independent carrier used for memory induction and/or revelation.

It has been previously reported that trinitrophenylated lipopolysaccharide (TNP-LPS), a thymus-independent (TI)-1 antigen, elicits an anamnestic response to TNP in C57BL/6 mice. The ability of these mice to mount a secondary response to TI-2 antigens was analyzed. Priming with DNP-Ficoll or DNP-Dextran, both TI-2 antigens, resulted in an increased frequency of TNP-binding B lymphocytes. Evidence is presented that memory cell-induction by DNP-Ficoll does not require functional T cells. The differentiation into antibody-forming cells (AFC) of memory cells generated by DNP-Dextran or DNP-Ficoll cannot be obtained by a challenge with either antigen. There was no indication that the lack of a secondary response to TI-2 antigens was related to suppressive T cells interfering with memory expression. Memory cells induced by DNP-Dextran or DNP-Ficoll can nevertheless be activated by TNP-LPS. In contrast to the restricted sensitivity of TNP-memory cells generated by TI-2 antigens, TNP-LPS-induced memory cells are indifferently susceptible to TI-1 or TI-2 antigenic stimulation. These results are discussed in terms of memory B-cell subpopulations.

Animals↗
PubMed1981

Immune unresponsiveness of spleen cells from lipopolysaccharide-treated mice to particulate thymus-dependent antigen. I. Evidence for differentiation signal defect.

The cellular basis of the immune unresponsiveness induced by lipopolysaccharide (LPS) was analyzed at the B and T cell level. The immunosuppressive effect of LPS is not related to altered B cell competence. Inhibition of antibody responses was observed only for thymus-dependent (TD) and not for thymus-independent antigens. In the presence of T cell-replacing factor (TRF), LPS-sensitized B lymphocytes respond to TD antigenic stimulation and differentiate into antibody-forming cells. Evidence is presented for a decreased helper activity of LPS-sensitized T lymphocytes and for a defective production of TRF in concanavalin A-stimulated spleen cells from LPS-treated mice. The implication of a cell compartment other than T is discussed.

Animals↗
PubMed1981

The immune response of CBA mice to OSRA, a peripheral protein from the sheep erythrocyte membrane.

The capacity of a membrane protein from sheep erythrocytes (osmotic shock released antigen: OSRA) to elicit an immune response in CBA mice was investigated. While all OSRA preparations tested are antigenically identical en indistinguishable with respect to physicochemical characteristics, they are not equally efficient in stimulating immunocompetent lymphocytes for antibody production upon a primary immunization (immunogenic versus antigenic OSRA). Both antibody-forming and (T and B) memory cells are generated in mice primed with immunogenic OSRA. Evidence is presented that the failure of antigenic OSRA to induce a primary response to SRBC determinants is related to its inability to stimulate unprimed T-cells. OSRA appears to be a major antigenic determinant of the sheep erythrocyte membrane since it specifically inhibits up to 60% of an anti-SRBC response.

Animals↗