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V K Kuchroo

Publications and source records attributed to V K Kuchroo.

At least 37 records · Page 2Linked to original sources
PubMed1999

B7-2 expressed on EL4 lymphoma suppresses antitumor immunity by an interleukin 4-dependent mechanism.

For T cells to become functionally activated they require at least two signals. The B7 costimulatory molecules B7-1 and B7-2 provide the "second signal" pivotal for T cell activation. In this report, we studied the relative roles of B7-1 and B7-2 molecules in the induction of antitumor immunity to the T cell thymoma, EL4. We generated EL4 tumor cells that expressed B7-1, B7-2, and B7-1+B7-2 by transfecting murine cDNAs. Our results demonstrate that EL4-B7-1 cells are completely rejected in syngeneic mice. Unlike EL4-B7-1 cells, we find that EL4-B7-2 cells are not rejected but progressively grow in the mice. A B7-1- and B7-2-EL4 double transfectant was generated by introducing B7-2 cDNA into the EL4-B7-1 tumor line that regressed in vivo. The EL4-B7-1+B7-2 double transfectant was not rejected when implanted into syngeneic mice but progressively grew to produce tumors. The double transfectant EL4 cells could costimulate T cell proliferation that could be blocked by anti-B7-1 antibodies, anti-B7-2 antibodies, or hCTLA4 immunoglobulin, showing that the B7-1 and B7-2 molecules expressed on the EL4 cells were functional. In vivo, treatment of mice implanted with double-transfected EL4 cells with anti-B7-2 monoclonal antibody resulted in tumor rejection. Furthermore, the EL4-B7-2 and EL4-B7-1+B7-2 cells, but not the wild-type EL4 cells, were rejected in interleukin 4 (IL-4) knockout mice. Our data suggests that B7-2 expressed on some T cell tumors inhibits development of antitumor immunity, and IL-4 appears to play a critical role in abrogation of the antitumor immune response.

Animals↗
PubMed1999

Mapping autoimmunity genes.

Rat and mouse models for the major human autoimmune/inflammatory diseases are under intense genetic scrutiny. Genome-wide linkage studies reveal that each model is regulated by multiple genetic loci. Many of these loci colocalize to homologous genomic regions associated with several different autoimmune diseases of mice, rats and humans. Candidate genes are being identified. Polymorphic alleles associated with these chromosomal segments may represent predisposing genetic elements common to a number of human diseases with very different clinical presentations.

Animals↗
PubMed1999

Changes in the strength of co-stimulation through the B7/CD28 pathway alter functional T cell responses to altered peptide ligands.

T cells require a TCR and a co-stimulatory signal for activation. We have examined the effect of the strength of TCR and co-stimulatory signals on proliferation and production of cytokines by differentiated T cell clones. The TCR signal was varied using antigen dose and altered peptide ligands. The co-stimulatory signal was varied by using as antigen-presenting cells, Chinese hamster ovary cell transfectants that express different levels of the B7-1 molecule with similar levels of MHC class II. Our results show that the level of co-stimulation has a profound effect on the response to an antigen, and that a strong co-stimulatory signal can convert a weak agonist into a full agonist and an agonist into a superagonist. Antigenicity is not absolute but a function of the strengths of the TCR and co-stimulatory signals. Increasing the strength of co-stimulation can lower antigen concentration required for maximal proliferative responses by T cell clones by 5 log. These results show that the level of expression of co-stimulatory molecules will profoundly regulate T cell clonal expansion and effector functions.

Animals↗
PubMed1998

IL-10 is critical in the regulation of autoimmune encephalomyelitis as demonstrated by studies of IL-10- and IL-4-deficient and transgenic mice.

Experimental autoimmune encephalomyelitis (EAE) and other organ-specific autoimmune diseases are induced by autoantigen-specific Th1 cells. In contrast, transfer of autoantigen-reactive Th2 cells that produce IL-4 and IL-10 can prevent and/or reverse EAE. The relative roles of these two Th2 cytokines in the regulation of EAE has not been evaluated. Utilizing IL-4 and IL-10 knockout mice deficient for these cytokines and IL-10 and IL-4 transgenic mice overexpressing these cytokines, we demonstrate that IL-10-deficient mice (IL-10(-/-)) are more susceptible and develop a more severe EAE when compared with IL-4-deficient mice (IL-4(-/-)) or wild-type mice. T cells from IL-10(-/-) mice exhibit a stronger Ag-specific proliferation, produce more proinflammatory cytokines (IFN-gamma and TNF-alpha) when stimulated with an encephalitogenic peptide, and induce very severe EAE upon transfer into wild-type mice. In contrast, while IL-4 transgenic mice develop similar disease compared with their nontransgenic littermates, mice transgenic for IL-10 are completely resistant to the development of EAE. Taken together, our data suggest that IL-10 plays a more critical role in the regulation of EAE by regulating autopathogenic Th1 responses.

Adoptive Transfer↗
PubMed1998

Expansion by self antigen is necessary for the induction of experimental autoimmune encephalomyelitis by T cells primed with a cross-reactive environmental antigen.

Cross-reactivity with environmental antigens has been postulated as a mechanism responsible for the induction of autoimmune disease. Experimental autoimmune encephalomyelitis is a T cell-mediated autoimmune disease model inducible in susceptible strains of laboratory animals by immunization with protein constituents of myelin. We used myelin proteolipid protein (PLP) peptide 139-151 and its analogues to define motifs to search a protein database for structural homologues of PLP139-151 and identified five peptides derived from microbial Ags that elicit immune responses that cross-react with this self peptide. Exposure of naive SJL mice to the cross-reactive environmental peptides alone was insufficient to induce autoimmune disease even when animals were treated with Ag-nonspecific stimuli (superantigen or LPS). However, immunization of SJL mice with suboptimal doses of PLP139-151 after priming with cross-reactive environmental peptides consistently induced experimental autoimmune encephalomyelitis. Furthermore, T cell lines from mice immunized with cross-reactive environmental peptides and restimulated in vitro with PLP139-151 could induce disease upon transfer into naive recipients. These data suggest that expansion by self Ag is required to break the threshold to autoimmune disease in animals primed with cross-reactive peptides.

Adoptive Transfer↗
PubMed1998

Heteroclitic proliferative responses and changes in cytokine profile induced by altered peptides: implications for autoimmunity.

Productive engagement of T cell receptors (TCRs) by cognate ligand (major histocompatibility complex plus peptide) leads to proliferation, differentiation, and the elaboration of effector functions. Altered peptides generated by single amino acid substitutions in the antigenic peptide have diverse effects on the outcome of the T cell response. We have generated an altered peptide (Q144) from an autoantigenic peptide of myelin proteolipid protein 139-151 by a single amino acid substitution (from tryptophan to glutamine) in the primary TCR contact at position 144 that is capable of inducing CD4(+) T cell responses in H-2(s) mice. By using a Q144-specific T cell clone (Q1.1B6), we see a hierarchy in T cell proliferation and cytokine production with various position 144 substituted peptides and have identified a peptide (L144) that hyperstimulates this T cell clone. In contrast to Q144, L144 induces maximal proliferation at 7 logs lower antigen concentration, induces greater cell death at higher antigen dose, and induces the secretion of cytokines not detected following stimulation with the cognate ligand. This heteroclitic T cell response associated with changes in cytokine profile was observed with several other T cell clones of different specificities. The L144 peptide also induces costimulation independent proliferation and cytokine production from the Q1.1B6 T cell clone. We describe this as a superagonist response. Such responses may have a role in the initiation of autoimmunity by promoting a proinflammatory environment following ligation of a cross-reactive TCR on autoreactive T cells.

Amino Acid Sequence↗
PubMed1998

CD28/B7 costimulation: a review.

The current model of T cell activation requires two signals. The first signal is specific, requiring T cell receptor recognition and binding to MHC/Antigen presented by an antigen-presenting cell. The second signal is nonspecific, resulting from the binding of B7 ligand on the antigen-presenting cell with its receptor, CD28, on the T cell. If both signals are provided, the T cell will proliferate and secrete cytokines. Recently, it has been shown that CTLA4, another receptor for B7 that is upregulated following T cell after activation, can deliver an inhibitory signal, downregulating T cell proliferation. The B7 family of ligands has two family members, B7-1 and B7-2. They both bind to CD28 and CTLA4, but they differ in their binding affinity, structure, and temporal expression. Considerable research has been done on the CD28/B7 costimulatory pathway. Different ways of manipulating this pathway could provide insights into the mechanism and treatment of opposing pathological states. Blocking the CD28/B7 pathway could result in immunosuppression, with implications for the treatment of autoimmune diseases, organ transplantation, and graft vs. host disease. Activating the CD28/B7 pathway could be useful for including the immune system to recognize and eliminate tumors that evade the immune system. Finally, the CD28/B7 pathway could be involved with maintaining immune tolerance, as recent studies suggest the preferential binding of the B7-CTLA4 pathway results in the down-regulation of the responding T cells. Thus, the B7/CD28/CTLA4 pathway has the ability to both positively and negatively regulate immune responses.

Abatacept↗
PubMed1997

Expression of a hypoglycosylated form of CD86 (B7-2) on human T cells with altered binding properties to CD28 and CTLA-4.

CD80 (B7-1) and CD86 (B7-2) on APC provide a major costimulatory signal through interactions with CD28 on T cells. Absent from resting human T cells, CD86 is up-regulated early upon T cell activation, whereas CD80 expression appears later. Whereas T cell expression of CD80 has been implicated in costimulation, the functional significance of CD86 expression on T cells is unclear. We now demonstrate that CD86 expressed on human CD4+ T cell clones does not provide a costimulatory signal for other CD4+ T cell clones. Binding studies using CD28-Ig and CTLA-4-Ig fusion proteins demonstrate that CD86 expressed on T cells has significantly reduced binding affinity for CTLA-4 and no detectable binding to CD28. Biochemical analysis demonstrates that post-translational modifications of CD86 in human T cells are different from those of CD86-transfected Chinese hamster ovary cells or EBV-transformed B cells, in that T cells express a hypoglycosylated form of CD86 on the surface membrane. Thus, our results suggest that while CD86 is expressed on a number of different cell types, its costimulatory function and affinity for its ligands may be regulated by cell type-specific post-translational modifications.

Abatacept↗
PubMed1997

Fas- and FasL-deficient mice are resistant to induction of autoimmune encephalomyelitis.

Experimental autoimmune encephalomyelitis (EAE) is an organ-specific autoimmune disease inducible in susceptible animals by myelin Ag-specific CD4+ Th1 cells. The mechanisms by which these cells induce inflammation and demyelination in the central nervous system (CNS) are incompletely understood. To determine the roles of Fas and FasL in the involvement of CNS autoimmune injury, we determined susceptibility to EAE of Fas-or FasL-deficient mice. Compared with wild-type mice, mice expressing lpr (Fas) and gld (FasL) mutations were relatively resistant to the development of clinical EAE, and this correlated with fewer inflammatory infiltrates and cells undergoing apoptosis in the CNS of the mutant mice. The gld and lpr mice, however, developed significant T cell responses with production of Th1 cytokines in response to the encephalitogenic myelin peptide. These results suggest that the Fas/FasL pathway plays a critical role in the development of EAE probably by mediating apoptosis within the target tissue.

Amino Acid Sequence↗
PubMed1997

Autopathogenic T helper cell type 1 (Th1) and protective Th2 clones differ in their recognition of the autoantigenic peptide of myelin proteolipid protein.

We previously generated a panel of T helper cell 1 (Th1) clones specific for an encephalitogenic peptide of myelin proteolipid protein (PLP) peptide 139-151 (HSLGKWLGHPDKF) that induces experimental autoimmune encephalomyelitis (EAE) upon adoptive transfer. In spite of the differences in their T cell receptor (TCR) gene usage, all these Th1 clones required W144 as the primary and most critical TCR contact residue for the activation. In this study, we determined the TCR contact residues of a panel of Th2/Th0 clones specific for the PLP peptide 139-151 generated either by immunization with the PLP 139-151 peptide with anti- B7-1 antibody or by immunization with an altered peptide Q144. Using alanine-substituted peptide analogues of the native PLP peptide, we show that the Th2 clones have shifted their primary contact residue to the NH2-terminal end of the peptide. These Th2 cells do not show any dependence on the W144, but show a critical requirement for L141/G142 as their major TCR contact residue. Thus, in contrast with the Th1 clones that did not proliferate to A144-substituted peptide, the Th2 clones tolerated a substitution at position 144 and proliferated to A144 peptide. This alternative A144 reactive repertoire appears to have a critical role in the regulation of autoimmune response to PLP 139-151 because preimmunization with A144 to expand the L141/G142-reactive repertoire protects mice from developing EAE induced with the native PLP 139-151 peptide. These data suggest that a balance between two different T cell repertoires specific for same autoantigenic epitope can determine disease phenotype, i.e., resistance or susceptibility to an autoimmune disease.

Adoptive Transfer↗
PubMed1997

A T cell receptor antagonist peptide induces T cells that mediate bystander suppression and prevent autoimmune encephalomyelitis induced with multiple myelin antigens.

Experimental autoimmune encephalomyelitis (EAE) induced with myelin proteolipid protein (PLP) residues 139-151 (HSLGKWLGHPDKF) can be prevented by treatment with a T cell receptor (TCR) antagonist peptide (L144/R147) generated by substituting at the two principal TCR contact residues in the encephalitogenic peptide. The TCR antagonist peptide blocks activation of encephalitogenic Th1 helper cells in vitro, but the mechanisms by which the antagonist peptide blocks EAE in vivo are not clear. Immunization with L144/R147 did not inhibit generation of PLP-(139-151)-specific T cells in vivo. Furthermore, preimmunization with L144/R147 protected mice from EAE induced with the encephalitogenic peptides PLP-(178-191) and myelin oligodendrocyte protein (MOG) residues 92-106 and with mouse myelin basic protein (MBP). These data suggest that the L144/R147 peptide does not act as an antagonist in vivo but mediates bystander suppression, probably by the generation of regulatory T cells. To confirm this we generated T cell lines and clones from animals immunized with PLP-(139-151) plus L144/R147. T cells specific for L144/R147 peptide were crossreactive with the native PLP-(139-151) peptide, produced Th2/Th0 cytokines, and suppressed EAE upon adoptive transfer. These studies demonstrate that TCR antagonist peptides may have multiple biological effects in vivo. One of the principal mechanisms by which these peptides inhibit autoimmunity is by the induction of regulatory T cells, leading to bystander suppression of EAE. These results have important implications for the treatment of autoimmune diseases where there are autopathogenic responses to multiple antigens in the target organ.

Animals↗
PubMed1997

B7.2 expressed by T cells does not induce CD28-mediated costimulatory activity but retains CTLA4 binding: implications for induction of antitumor immunity to T cell tumors.

The B7 family of costimulatory molecules provides the second signal necessary for activation of T cells. In the absence of the second signal, responding T cells become anergic. Although predominantly expressed on professional APCs, recent evidence shows that the B7 molecules are also expressed on T cells. To study the functions of B7 molecules on T cells, we transfected murine B7.1 (CD80) and B7.2 (CD86) cDNAs into the EL4 T cell thymoma cell line and examined the transfectants for their ability to costimulate T cell proliferation in vitro and to induce antitumor immunity in vivo. Here we show that although EL4-B7.1 cells costimulate T cells and induce tumor regression, EL4-B7.2 transfectants failed to costimulate T cell proliferation or induce tumor regression. To understand the cellular basis for this difference, we examined the binding of EL4-B7.1 and EL4-B7.2 to CTLA4 and CD28. Whereas EL4-B7.1 cells bound both CTLA4-Ig and CD28-Ig, EL4-B7.2 transfectants preferentially bound CTLA4-Ig, but not CD28-Ig. Similar binding data were obtained with freshly isolated murine T cells, which have been shown to constitutively express B7.2. Our data suggest, therefore, that B7.2 expressed on T cells may not costimulate but instead inhibit the T cell response by preferential binding to CTLA4.

Abatacept↗
PubMed1997

T cell recognition of self and altered self antigens.

T lymphocytes bearing alpha/beta TCR recognize antigens in the context of self MHC molecules, and this recognition leads to growth, differentiation, and effector functions. Recently, it has become clear that altered peptides generated by single amino acid substitution of the antigenic peptide can alter the patterns of differentiation and effector functions of the responding T lymphocytes. By defining the pattern of recognition and residues of the cognate ligand that bind to the TCR, altered peptide ligands (APLs) have been generated by selectively substituting the TCR contact residues in the antigenic peptide. These APLs have been utilized in vitro to study the biology of T cell function and alterations in the T cell signaling pathway. In vivo APLs have been utilized to study the mechanism of positive selection in the thymus and in regulation of autoimmune diseases. With this basic knowledge, APLs that can either hypo- or hyper-stimulate T cell function can be generated that can specifically alter (inhibit or enhance) immune responses in vivo in autoimmune diseases and cancers.

Amino Acid Sequence↗
PubMed1996

Inheritance of susceptibility to experimental autoimmune encephalomyelitis.

Experimental autoimmune encephalomyelitis is a disease of the central nervous system that can be readily induced in a variety of species by immunization with myelin proteins. It is one of the most commonly studied models of cell-mediated autoimmune disease and consequently has been important in the elucidation of many immunological functions in vivo. Nevertheless, very little is understood about the genetic and environmental factors that control the disease. Several groups have begun undertaking systematic genetic analyses in mice to identify loci that associate with increased susceptibility to disease. In this review, we will summarize the work that has been done to understand the genetic predisposition that makes certain inbred animals susceptible to disease and others resistant, and we will discuss some of the difficulties in the genetic analysis that have arisen due to the complexities of this disease model.

Animals↗
PubMed1996

Genetic analysis of susceptibility to experimental autoimmune encephalomyelitis in a cross between SJL/J and B10.S mice.

Experimental autoimmune encephalomyelitis (EAE), a model for human multiple sclerosis, is a T cell-mediated autoimmune disease that can be induced in experimental animals by immunization with myelin Ags. Inbred strains of mice show varying degrees of susceptibility to EAE, indicating that susceptibility is an inherited trait. To define the genetic factors that control susceptibility to EAE, we performed linkage analysis on the first backcross (BC1) between highly susceptible SJL/J mice and resistant B10.S mice, both of which are of the H-2s haplotype. Mice were immunized for disease with encephalitogenic myelin proteolipid protein peptide 139 to 151, and analysis was performed on 68 backcross mice showing the severe disease phenotype (disease score > or = 3)and 68 backcross mice of the resistant phenotype (no clinical or histologic signs of disease) using microsatellite markers covering >98% of the genome. We found the strongest linkage (p = 0.001) with clinical disease at two loci: one at the telomeric end of chromosome 2, and another near the center of chromosome 3. In addition, several other regions showing some evidence of linkage (p < or = 0.05) with clinical disease were found.

Animals↗
PubMed1996

Oral tolerance in myelin basic protein T-cell receptor transgenic mice: suppression of autoimmune encephalomyelitis and dose-dependent induction of regulatory cells.

Orally administered antigens induce a state of immunologic hyporesponsiveness termed oral tolerance. Different mechanisms are involved in mediating oral tolerance depending on the dose fed. Low doses of antigen generate cytokine-secreting regulatory cells, whereas high doses induce anergy or deletion. We used mice transgenic for a T-cell receptor (TCR) derived from an encephalitogenic T-cell clone specific for the acetylated N-terminal peptide of myelin basic protein (MBP) Ac-1-11 plus I-Au to test whether a regulatory T cell could be generated from the same precursor cell as that of an encephalitogenic Th1 cell and whether the induction was dose dependent. The MBP TCR transgenic mice primarily have T cells of a precursor phenotype that produce interleukin 2 (IL-2) with little interferon gamma (IFN-gamma), IL-4, or transforming growth factor beta (TGF-beta). We fed transgenic animals a low-dose (1 mg x 5) or high-dose (25 mg x 1) regimen of mouse MBP and without further immunization spleen cells were tested for cytokine production. Low-dose feeding induced prominent secretion of IL-4, IL-10, and TGF-beta, whereas minimal secretion of these cytokines was observed with high-dose feeding. Little or no change was seen in proliferation or IL-2/IFN-gamma secretion in fed animals irrespective of the dose. To demonstrate in vivo functional activity of the cytokine-secreting cells generated by oral antigen, spleen cells from low-dose-fed animals were adoptively transferred into naive (PLJ x SJL)F1 mice that were then immunized for the development of experimental autoimmune encephalomyelitis (EAE). Marked suppression of EAE was observed when T cells were transferred from MBP-fed transgenic animals but not from animals that were not fed. In contrast to oral tolerization, s.c. immunization of transgenic animals with MBP in complete Freund's adjuvant induced IFN-gamma-secreting Th1 cells in vitro and experimental encephalomyelitis in vivo. Despite the large number of cells reactive to MBP in the transgenic animals, EAE was also suppressed by low-dose feeding of MBP prior to immunization. These results demonstrate that MBP-specific T cells can differentiate in vivo into encephalitogenic or regulatory T cells depending upon the context by which they are exposed to antigen.

Administration, Oral↗