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Biomedical subjects

A Lanzavecchia

Publications and source records attributed to A Lanzavecchia.

At least 127 records · Page 7Linked to original sources
PubMed1991

Selection by two powerful antigens may account for the presence of the major population of human peripheral gamma/delta T cells.

V gamma 9/V delta 2 cells represent a fraction of human gamma/delta cells that is expanded after birth in the periphery, carries markers of activated cells, and becomes a major population in peripheral blood. We found that these cells do not comprise a single population but actually represent two nested sets, the smaller of which, specific for Mycobacterium tuberculosis-pulsed antigen-presenting cells (APC), is contained in a larger set specific for an antigen found on the Molt-4 lymphoma. The larger set, representing 40-80% of all blood gamma/delta cells, is comprised of cells bearing the V gamma 9/C gamma 1 chain. Cells in the smaller, included set have an additional requirement for V delta 2 (and probably for certain permissive junctional regions, since a very small percentage of V gamma 9/V delta 2 cells do not react against mycobacteria-pulsed APC). Optimal stimulation by mycobacteria is dependent on the presence of APC, and is not restricted by classical major histocompatibility complex molecules. Some of the V gamma 9/V delta 2 mycobacteria-specific clones are also stimulated by APC pulsed with different bacteria, such as Listeria monocytogenes and Escherichia coli, indicating that the population includes several different patterns of reactivity. These data establish a relationship in humans between specificity and V gamma/V delta gene usage, and offer an explanation for the peripheral expansion of these gamma/delta cells.

Antigen-Presenting Cells↗
PubMed1991

Efficient and selective presentation of antigen-antibody complexes by rheumatoid factor B cells.

Using Epstein-Barr virus B cell clones and antigen-specific T cell clones, we asked how antigen-antibody complexes are handled by B cells. We found that the only B cells capable of efficient presentation of antigen-antibody complexes are those that bind the complexes via membrane immunoglobulin, i.e., rheumatoid factor-producing B cells and, to a lower extent, antigen-specific B cells. On the contrary, nonspecific B cells, although capable of binding antigen-antibody complexes, fail to present them to T cells. Thus, rheumatoid factor B cells can present any antigen in the context of an immune complex and be triggered by T cells specific for a variety of foreign antigens. These results demonstrate a mechanism of intermolecular help that may be responsible for the production of rheumatoid factor and possibly of other types of autoantibodies.

Antigen-Antibody Complex↗
PubMed1991

Bispecific single chain molecules (Janusins) target cytotoxic lymphocytes on HIV infected cells.

The human immunodeficiency virus type 1 (HIV-1) uses cell surface CD4 as a receptor to infect susceptible cells. Therefore, different forms of soluble CD4 (sCD4) molecules have been developed recently for potential therapeutic purposes. Here we describe a novel design of sCD4 molecules which exploit cytotoxic T cells as their effector function. The principle of bispecific antibodies was exploited and further developed to create new bispecific reagents which could retarget cytotoxic T cells of any specificity and thus, induce killing of HIV-1 infected cells. The most advanced molecules, Janusins, contain in one polypeptide chain the first two N-terminal CD4 domains and single chain combining site against the human CD3 complex (FvCD3).

Amino Acid Sequence↗
PubMed1991

Chemical and functional analysis of MHC class II-restricted T cell epitopes.

Various aspects of antigen degradation and presentation are reviewed, in particular with respect to fragmentation of native vs. denatured proteins, different enzymatic machinery present in different cells and individuals, characterization of epitopes and their persistence on antigen-presenting cells as well as their capacity to interact with different MHC class II molecules. Finally, the structure of antigenic peptides is discussed.

Animals↗
PubMed1990

T cell activation by a bispecific anti-CD3/anti-major histocompatibility complex class I antibody.

A bispecific anti-CD3/anti-major histocompatibility complex (MHC) class I antibody (Ab) that is able to activate human T cells in the absence of a second signal has been used to compare activation by this Ab to signaling by anti-CD3 Ab or by antigen (Ag). We have studied early, intermediate and late events that occur after triggering of a tetanus toxoid-specific T cell clone. While bivalent anti-CD3 Ab induce transient (less than 20 min) intracellular Ca2+ concentration increases, the bispecific Ab, like antigen-presenting cells plus Ag, produces sustained (greater than 2 h) elevated intracellular Ca2+ concentration. In addition, while the anti-CD3 Ab only induces low levels of c-myc mRNA lasting less than 3 h, the bispecific Ab induces high levels which are maintained for at least 8 h after triggering. Late events, such as interleukin 2 receptor expression and proliferation, occurring more than 20 h after activation, were seen only when T cells were stimulated by bispecific Ab or by antigen-presenting cell and Ag. Cells activated by linking T cell receptor (TcR)/CD3 to MHC class I antigens could not be activated by cross-linking the MHC and TcR/CD3 structures separately. Therefore, we propose that the bispecific Ab functions by modifying the membrane dynamics of the TcR/CD3 complex, rather than by the generation of a second signal through class I antigens.

Antigen-Presenting Cells↗
PubMed1989

Processing of tetanus toxin by human antigen-presenting cells. Evidence for donor and epitope-specific processing pathways.

Human T cell clones specific for epitopes 830-843 and 947-967 of tetanus toxin can be differentially activated in vitro when APC (PBL or LCL) from different donors are pulsed with tetanus toxin. Although PBL tested do not seem to exhibit substantial differences in the number of precursor T cells specific for these epitopes, APC from the same donors activate clone KT-2 specific for peptide 830-843 but not clone KT-30 specific for peptide 947-967. These APC express the proper restriction element because they can present the corresponding synthetic peptides. The failure to present a particular epitope might, however, be explained by the absence or presence of a protease(s) required for Ag presentation that may vary for different epitopes. Indeed, the protease inhibitor leupeptin was found to inhibit activation of KT-2 but not KT-30 T cell clone by the KK.35 B cell line normally capable of presenting either epitope. In summary, these data suggest that tetanus toxin processing and epitope formation by APC is distinct in different donors and for different epitopes.

Antigen-Presenting Cells↗
PubMed1989

Molecular analysis of human gamma/delta+ clones from thymus and peripheral blood.

We analyzed the V gamma and V delta gene usage in TCR-gamma/delta-bearing T cell clones isolated from human peripheral blood and postnatal thymus using V-specific mAbs and Southern and Northern analyses. In peripheral blood most of the gamma/delta cells express the V gamma 9-JP-C gamma 1 chain paired with a delta chain bearing the V delta 2 gene product. This heterodimer is very rare in the postnatal thymus, where a different and less restricted pairing of V gamma 9 and V delta 2 chains is found. These findings indicate that physical constraints cannot explain the overrepresentation of a particular V gamma 9-JP/V delta 2 heterodimer in the peripheral blood, and we discuss alternative mechanisms that may account for this differential distribution. In addition, this analysis allowed us to map the specificity of the delta TCS1 mAb to V delta 1-J delta 1 and to identify at least five different expressed V delta genes.

Antibodies, Monoclonal↗
PubMed1989

A novel and simple procedure for determining T cell epitopes in protein antigens.

A human T cell epitope was mapped on tetanus toxin by the use of a simple method. Tetanus toxin peptide preparations were produced by various specific chemical and proteolytic cleavages. T cell proliferative response to these peptide preparations was assayed to determine which amino acid residues were present or absent in the T cell epitope. Cyanogen bromide-derived tetanus toxin peptides were separated by electrophoresis and transferred onto nitrocellulose. T cell proliferative response to nitrocellulose fragments was assayed to determine the molecular weight of the antigenic tetanus toxin peptide. The combination of the two procedures allowed us to define a 21-mer tetanus toxin peptide recognized by the T cell clone. This method represents an easily performed alternative for the mapping of T cell epitopes on protein antigen.

CD4-Positive T-Lymphocytes↗
PubMed1989

Triggering T cells by otherwise inert hybrid anti-CD3/antitumor antibodies requires encounter with the specific target cell.

We used a purified bispecific antibody (Ab) against CD3 and an ovarian carcinoma (OVCA) antigen to ask whether the binding of a monovalent ligand to CD3 can induce triggering of T cells. In the presence of OVCA cells, this Ab bridges the CD3 complex to the target cell and triggers proliferation and cytotoxicity in T cells. In the absence of target cells, however, this monovalent Ab, even when bound to T cells at high levels, fails to induce any increase in cytosolic Ca2+, nor does it induce responsiveness to IL-2 or modulation of the CD3 complex. Because it is inert when bound monovalently, this hybrid Ab can be used to arm in vitro CTL clones, which then retain the capacity to kill the specific tumor for up to 2 d.

Antibodies, Monoclonal↗
PubMed1989

Establishment of human double-positive thymocyte clones.

Human thymocytes were sorted according to the expression of CD4 and CD8 molecules and clones representing the four subpopulations (DP, DN, and single CD4 or CD8 positive) were established. DP clones can be maintained for long periods in tissue culture and give rise to a variable percentage of SP variants. These variants, when isolated and further expanded, do not revert to a DP phenotype. DP clones express a functional TCR-CD3 complex, suggesting that this molecule can interact with the thymic microenvironment during T cell differentiation.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1989

In vivo localization of a bispecific antibody which targets human T lymphocytes to lyse human colon cancer cells.

A bispecific MAb was derived from the fusion of a hybridoma producing MAb CD3 with a hybridoma producing MAb L-DI (which is directed against a 41-kDa glycoprotein expressed in most gastro-intestinal and pancreatic carcinomas). Bispecific antibody molecules were isolated from parental antibody molecules by the use of hydroxylapatite-HPLC and shown to target human cytolytic T lymphocytes, irrespective of their original specificity, to specifically lyse human colon carcinoma cells. Localization studies in vivo using nude mice bearing human colon carcinoma xenografts showed significant accumulation of the HPLC-purified 125I-labelled bispecific antibodies into the tumor compared to 131I-labelled control CD3 antibody.

Animals↗
PubMed1989

Delineation of several DR-restricted tetanus toxin T cell epitopes.

We have characterized five human T cell clones specific for tetanus toxin. The combination of different techniques allowed us to precisely map two T cell epitopes within fragments 830-843 and 1273-1284 of tetanus toxin, as formally demonstrated by the use of corresponding synthetic peptides. The three other T cell clones were specific for regions 2-602, 604-742, and 865-1315 of tetanus toxin, respectively. The five T cell clones were shown to be restricted to HLA-DR Ag. Furthermore, the allele of HLA-DR utilized by the various epitopes has been determined. The use of HLA-DR-transfected L cells as APC directly demonstrated that two epitopes, one of which represented by fragment 1273-1284, were recognized in association with HLA-DRw52a. For the other three T cell epitopes, the data strongly suggested they were recognized in association with HLA-DR5. Finally, a sixth T cell clone was shown to be specific for tetanus toxoid, the vaccinal preparation of tetanus toxin, and not for other tetanus toxin fragments. This indicated that immunization with tetanus toxoid probably elicits a T cell response directed only in part against native tetanus toxin.

Alleles↗
PubMed1989

Universally immunogenic T cell epitopes: promiscuous binding to human MHC class II and promiscuous recognition by T cells.

To understand the effect of human MHC class II polymorphism on antigen recognition, we analyzed the memory T cell response to three tetanus toxin epitopes defined by three short synthetic peptides (p2, p4 and p30). We found that p2 and p30 are universally immunogenic, since they are recognized by all primed donors, irrespective of their MHC haplotypes. The analysis of specific clones indicates that both peptides are very promiscuous in their capacity to bind to class II. p30 can be recognized in association with DRw11(5), 7, 9 and with DPw2 and DPw4, while p2 can be recognized in association with DR1, DRw15(2), DRw18 (3), DR4Dw4, DRw11(5), DRw13(w6), DR7, DRw8, DR9, DRw52a and DRw52b. On the contrary, the third peptide, p4, can be recognized by only half of the donors in association with only DRw52a and DRw52c. Analysis of truncated peptides shows that p30 contains three distinct epitopes, each recognized in association with different class II molecules. Therefore, the restriction specificity is already set at the level of the peptide-MHC complex and, in all cases, T cells discriminate p30 bound to different class II molecules. On the contrary, p2 contains only one epitope, which is recognized in association with all DR molecules. In this case we found two different restriction patterns. Some clones are monogamous, since they recognize the peptide in association with one DR allele, while others are promiscuous, since they recognize by peptide in association with several different DR molecules. Thus, in this case, the restriction specificity is also set at the level of the T cell receptor. We suggest that both the promiscuous binding of peptides and the promiscuous recognition by T cells are dependent on the particular structure of the DR molecules, having a monomorphic alpha chain associated with a polymorphic beta chain.

Alleles↗