Induction of Regulatory CD4+ Cells and Prolongation of Fully Major Histocompatibility Complex Mismatched Murine Cardiac Allograft by Shigyakusan.

Shigyakusan (also known as Tsumura Japan [TJ]-35) is composed of peony, bitter orange, licorice, and Bupleuri radix is used for cholecystitis and gastritis as an anti-inflammatory agent. We investigated the effect of TJ-35 on alloimmune response in a murine heart transplantation model. CBA mice that underwent transplantation of a C57BL/6 (B6) heart were assigned to four groups: no treatment, TJ-35-exposed, each component-exposed, or each component missing-exposed. The four groups above each received oral administration of TJ-35, each component, or TJ-35 with each component missing from the day of transplantation until 7 days, respectively. Untreated CBA recipients rejected B6 cardiac grafts acutely (median survival time [MST], 7 days). TJ-35-exposed CBA recipients had significantly prolonged B6 allograft survival (MST, 20.5 days). However, MSTs of CBA recipients that had been administered each component and TJ-35 with each component missing did not reach that of TJ-35-exposed recipients. Adoptive transfer of CD4+ splenocytes from TJ-35-exposed primary allograft recipients resulted in significant prolonged allograft survival in naïve secondary recipients (MST, 63 days). Flow cytometry studies showed that the percentage of CD4+CD25+Foxp3+ cell population was increased in TJ-35-exposed CBA recipients. In conclusion, TJ-35-induced prolongation of fully allogeneic cardiac allografts and may generate regulatory CD4+CD25+Foxp3+ cells in our model. The effect seemed to require all components of TJ-35.

The role of T-cell receptor recognition of peptide:MHC complexes in the formation and activity of Foxp3⁺ regulatory T cells.

Foxp3(+) regulatory T (Treg) cells are required to prevent the immune system from spontaneously mounting a severe autoaggressive lymphoproliferative disease and can modulate immune responses in a variety of settings, including infections. In this review, we describe studies that use transgenic mice to determine how signals through the T-cell receptor (TCR) contribute to the development, differentiation, and activity of Treg cells in in vivo settings. By varying the amount and quality of the self-peptide recognized by an autoreactive TCR, we have shown that the interplay between autoreactive thymocyte deletion and Treg cell formation leads to a Treg cell repertoire that is biased toward low abundance agonist self-peptides. In an autoimmune disease setting, we have demonstrated that diverse TCR specificities can be required in order for Treg cells to prevent disease in a mouse model of autoimmune inflammatory arthritis. Lastly, we have shown that Treg cells initially selected based on specificity for a self-peptide can be activated by TCR recognition of a viral peptide, and that they can acquire a specialized phenotype and suppress antiviral effector cell activity at the site of infection. These studies provide insights into the pivotal role that TCR specificity plays in the formation and activity of Treg cells.

Aqueous extract of Phyllanthus niruri (Euphorbiaceae) enhances the phenotypic and functional maturation of bone marrow-derived dendritic cells and their antigen-presentation function.

Decoctions of Phyllanthus niruri (PN) (Fam. Euphorbiaceae) is promoted in traditional medicine of Africa, Asia, and South America as beneficial supplement for different infectious diseases, especially for viral hepatitis, tumor, and for immune compromised patients. This stimulated the interest in understanding the mechanisms by which the whole extract of the plant could stimulate the immune system. Dendritic cells (DCs) are professional antigen-presenting cells and provide a link between the innate and the adaptive immune responses. In the present study, the effects of lyophilized aqueous extract of PN on structural and functional maturation of murine bone marrow-derived DCs (BM-DCs) were investigated. Bone marrow cells were cultured in the presence of granulocyte macrophage-colony stimulating factor and interleukin-4 (IL-4) and the generated immature DCs were stimulated with PN (25, 50, and 100 microg/mL) or lipopolysaccharide (10 microg/mL) for 48 h. Results showed that treatment with PN increased the expression of major histocompatibility complex-II and the various makers for DCs maturation (CD40), activation (CD83), and costimulation (CD86) in a concentration-dependent manner. Consistent with the increase in phenotypic makers, functional maturation assay showed that treatment of BM-DCs with PN caused a decrease in fluorescein isothiocyanate-dextran pinocytosis and an increase in IL-12 in the supernatant. In a transgenic T-cell activation model, PN-treated BM-DCs presented Ova antigen to Ova-specific CD8(+) T cells from OT-1 mice more efficiently as demonstrated by increased T-cells proliferation and IL-2 production. Therefore, PN enhances the structural and functional maturation of BM-DCs and their antigen-presenting function. These effects are relevant in immunodeficient conditions, tumor control, and in infectious diseases.

A new twist in TCR diversity revealed by a forbidden alphabeta TCR.

We report crystal structures of a negatively selected T cell receptor (TCR) that recognizes two I-A(u)-restricted myelin basic protein peptides and one of its peptide/major histocompatibility complex (pMHC) ligands. Unusual complementarity-determining region (CDR) structural features revealed by our analyses identify a previously unrecognized mechanism by which the highly variable CDR3 regions define ligand specificity. In addition to the pMHC contact residues contributed by CDR3, the CDR3 residues buried deep within the V alpha/V beta interface exert indirect effects on recognition by influencing the V alpha/V beta interdomain angle. This phenomenon represents an additional mechanism for increasing the potential diversity of the TCR repertoire. Both the direct and indirect effects exerted by CDR residues can impact global TCR/MHC docking. Analysis of the available TCR structures in light of these results highlights the significance of the V alpha/V beta interdomain angle in determining specificity and indicates that TCR/pMHC interface features do not distinguish autoimmune from non-autoimmune class II-restricted TCRs.

Dendritic cells break tolerance and induce protective immunity against a melanocyte differentiation antigen in an autologous melanoma model.

Tyrosinase-related protein (TRP) 2 belongs to the melanocyte differentiation antigens and has been implicated as a target for immunotherapy of human as well as murine melanoma. In the current report, we explored the efficacy of nonmutated epitopes with differential binding affinity for MHC class I, derived from mouse TRP2 to induce CTL-mediated, tumor-reactive immunity in vivo within the established B16 melanoma model of C57BL/6 mice. The use of nonmutated TRP2-derived epitopes for vaccination provides a mouse model that closely mimics human melanoma without introduction of xenogeneic or otherwise foreign antigen. The results demonstrate that vaccination with TRP2 peptide-loaded bone marrow-derived dendritic cells (DCs) results in activation of high avidity TRP2-specific CTLs, displaying lytic activity against both B16 melanoma cells and normal melanocytes in vitro. In vivo, protective antitumor immunity against a lethal s.c. B16 challenge was observed upon DC-based vaccination in this fully autologous tumor model. The level of protective immunity positively correlated with the MHC class I binding capacity of the peptides used for vaccination. In contrast, within this autologous model, vaccination with TRP2 peptide in Freund's adjuvant or TRP2-encoding plasmid DNA did not result in protective immunity against B16. Strikingly, despite the observed CTL-mediated melanocyte destruction in vitro, melanocyte destruction in vivo was sporadic and primarily restricted to minor depigmentation of the vaccination site. These results emphasize the potency of DC-based vaccines to induce immunity against autologous tumor-associated antigen and indicate that CTL-mediated antitumor immunity can proceed without development of adverse autoimmunity against normal tissue.

Increase in the immunogenicity of HIV peptide antigens by chemical linkage to polytuftsin (TKPR40).

The use of synthetic peptide antigens in human prophylaxis still suffers from the very important problem of finding suitable carriers devoid of side effects. A desirable carrier for use in humans would be poorly immunogenic by itself, yet it would enhance the immune response to the peptide antigen. In the study reported herein, we examined the role of polytuftsin (TKPR40), a synthetic polymer of the natural immunomodulator tuftsin, as a carrier for synthetic peptides of HIV derived from the gp41 and gp120 proteins. Chimeric immunogens were constructed by chemical linkage between synthetic peptides of HIV and polytuftsin. These were employed for immunization of mice of different MHC haplotypes, and the humoral and cellular immune responses developed against the peptides were assessed by measuring total IgG, IgG, subclasses, T-cell proliferation, and in vitro cytokine release. A significantly stronger immune response was observed in mice immunized with the peptide-polytuftsin conjugates than in mice receiving the peptide dimers (peptide-peptide). Peptide-polytuftsin conjugates induced IgG2a and IgG2b isotype switching after both primary and secondary immunization. In addition, there was a positive correlation between the amounts of cytokines and the shift in the IgG isotypes. These data suggest that the use of polytuftsin as a carrier may increase the immune response against poorly immunogenic synthetic peptides.

Peptide based cytotoxic T-cell vaccines; delivery of multiple epitopes, help, memory and problems.

Synthetic CD8+ cytotoxic T-lymphocyte (CTL) peptide epitope based vaccines are being developed against a number of human diseases. Here we describe extensive preclinical testing of peptide epitope vaccines formulated with a protein as a source of CD4 help and Montanide ISA 720, an adjuvant currently in human clinical trials. Such water-in-oil formulations could effectively co-deliver several peptide epitopes and simultaneously induce multiple independent CTL responses. The efficiency of CTL induction by some peptides was, however, dependent on the aqueous buffer conditions, with poor performance correlating with non-covalent peptide oligomerisation. Any of a number of proteins currently used in human vaccines could supply CD4 help and no difference in CTL induction was obtained if the CD4 response was amnestic or a primary. Peptide immunisation was found to induce long term CTL memory and the recall of protective responses did not depend on an amnestic CD4 response. Slow pyroglutamic acid formation and rapid oxidation of methionine residues was observed in water-in-oil formulations, however, the latter had no effect on CTL induction. These data highlight the need to monitor for potential deleterious chemical events and interpeptide interactions, but illustrate that peptide based vaccination can effectively deliver multiple epitopes, in conjunction with any protein, and induce protective memory.

Major histocompatibility complex and T cell receptor interaction of the P91A tum- peptide.

The P91A antigen was identified following mutation of P1 mastocytoma cells. The peptide epitope is encoded by a mutant form of the S3 subunit of the PA700 proteasome regulatory complex. P91A stimulates a strong CD8+ T cell response when expressed on tumor cells or normal tissue and P91A-specific T cells express a restricted range of T cell receptors. Although it is a strong Ld-binding peptide, P91A does not conform to the established motif for this major histocompatibility complex (MHC) molecule and this has hampered elucidation of the precise epitope. Ld predominantly associates with nonamer peptides; however, using a variety of complementary approaches, the P91A epitope is identified as the octamer QNHRALDL. In the absence of the Ld motif residue proline at position 2, residues 5-7 are primarily involved in MHC interaction. P91A is thus atypical in its interaction with Ld. Residues 1, 3, and 4 are found to influence T cell recognition of P91A. Definition of the P91A peptide will allow studies on P91A processing and interactions of the P91A peptide/MHC complex with T cell receptors of differing avidity to establish the basis for restricted T cell receptor usage. The basis for the failure of the P91A tum+ peptide (QNRRALDL) to bind to Ld is addressed by molecular modeling.

Susceptibility of DA rats to arthritis induced with adjuvant oil or rat collagen is determined by genes both within and outside the major histocompatibility complex.

Inbred DA rats are remarkably susceptible to arthritis induced both by non-immunogenic mineral oil only (OIA) and by rat collagen II together with mineral oil (rCIA). This fact enables interesting studies concerning which DA genes are associated with the arthritogenicity of adjuvant oil and collagen, respectively. In this paper the authors have investigated the role of genes within and outside the major histocompatibility complex (MHC), in this respect by comparative susceptibility studies in inbred rat strains (DA, LEW) and MHC-congenic strains (DA.1I, DA.1O, DA.1M, DA.1H, LEW.1AV1, PVG.1AV1). The authors confirm earlier reports on the arthritis-promoting nature of the DA MHC haplotype (RT1av1), but demonstrate that neither OIA nor rCIA is restricted to this haplotype or its class II alleles (Ba, Da). A decisive role of non-MHC genes in determining susceptibility is also clear since the PVG.1AV1 strain, with the permissive RT1av1 haplotype, is resistant to both arthritis models. In conclusion, the authors demonstrate that the susceptibility of DA rats to OIA and rCIA is determined similarly, by permissive genes both within and outside the MHC. Second, and more interesting from a general perspective, the investigation demonstrates a notable influence of genes within and outside the MHC on the pathogenic capacity of a non-immunogenic adjuvant oil. This adjuvant is in turn a critical component in provocations leading not only to rCIA but also to many other experimental autoimmune diseases where the influence of 'adjuvant response genes' is rarely considered.

HLA-B27 heavy chains contribute to spontaneous inflammatory disease in B27/human beta2-microglobulin (beta2m) double transgenic mice with disrupted mouse beta2m.

MHC class I allele, HLA-B27, is strongly associated with a group of human diseases called spondyloarthropathies. Some of these diseases have an onset after an enteric or genitourinary infection. In the present study, we describe spontaneous disease in HLA-B27 transgenic mice where endogenous beta2-microglobulin (beta2m) gene was replaced with transgenic human beta2m gene. These mice showed cell surface expression of HLA-B27 similar to that of human peripheral blood mononuclear cells. In addition, free heavy chains (HCs) of HLA-B27 were also expressed on thymic epithelium and on a subpopulation of B27-expressing PBLs. These mice developed spontaneous arthritis and nail changes in the rear paws. Arthritis occurred primarily in male animals and only when mice were transferred from the pathogen-free barrier facility to the conventional area. Transgenic mice expressing HLA-B27 with mouse beta2m have undetectable levels of free HCs on the cell surface and do not develop arthritis. In vivo treatment with anti-HC-specific antibody delayed the onset of disease. Our data demonstrate specific involvement of HLA-B27 'free' HCs in the disease process.

Identification of T-cell epitopes of Lol p 9, a major allergen of ryegrass (Lolium perenne) pollen.

T-cell recognition of Lol p 9, a major allergen of ryegrass pollen, was investigated by using a T-cell line and T-cell clones generated from the peripheral blood of an atopic donor. The T-cell line reacted with purified Lol p 9, as well as with crude ryegrass pollen extract, but failed to cross-react with Bermuda grass pollen extract. All of six T-cell clones generated from this line proliferated in response to Lol p 9. Epitope mapping was carried out with a panel of 34 overlapping synthetic peptides, which spanned the entire sequence of the Lol p 9 12R isoform. The T-cell line responded to two of the peptides, Lol p 9 (105-116) and Lol p 9 (193-204), whereas reactivity with one or other of these peptides was shown by five T-cell clones. These two peptides contained sequences consistent with motifs previously reported for major histocompatibility complex class II-restricted peptides. HLA antibody blocking studies showed that presentation of peptide Lol p 9 (105-116) to one T-cell clone was HLA-DR-restricted; this clone expressed a T helper cell phenotype (CD3+, CD4+) and the T-cell receptor alpha beta. The identification of immunodominant T-cell epitope(s) on allergens is essential for devising safer and more effective immunotherapy strategies, which can interrupt the chain of events leading to allergic disease.

Differential mycobacterial 65-kDa heat shock protein T cell epitope recognition after adjuvant arthritis-inducing or protective immunization protocols.

Immunization of Lewis rats with heat-killed Mycobacterium tuberculosis (Mt) in mineral oil induces adjuvant arthritis (AA), associated with T cell responses to residues 180-188 of the mycobacterial 65-kDa heat shock protein (hsp65). Preimmunization with hsp65 protects rats against AA and other forms of arthritis. Several explanations for these protective effects have been proposed, including enhanced responsiveness to protective epitopes in hsp65, down-regulation of T cell responses to the 180-188 epitope, and activation of self-hsp60-reactive T cells. To assess the potential of these hypotheses, we analyzed hsp65 T cell epitopes recognized after immunization of Lewis rats with Mt or hsp65. Here we identify nine RT1.B1-restricted T cell epitopes in hsp65. Mt immunization induced T cell responses in which the 180-188 epitope was dominant, whereas hsp65 immunization resulted in a co-dominance of this and two further epitopes, 216-225 and 226-235. Two minor epitopes were recognized after hsp65 but not Mt immunization. These results indicate that hsp65 preimmunization does not down-regulate responses to the AA-associated epitope, but does enhance responses to several hsp65 epitopes that are minor or absent after the AA-inducing immunization protocol. Cross-reactive T cell recognition of hsp65 and rat hsp60 was limited to a single epitope (256-265), recognized after hsp65 immunization, but poorly recognized after Mt immunization. This study provides the necessary basis for elucidating the T cell events involved in the protective effects of hsp65 preimmunization.

[The onset mechanism of experimental autoimmune uveoretinitis induced by interphotoreceptor retinoid-binding protein].

In order to analyze the onset mechanism of experimental autoimmune uveoretinitis (EAU), two experimental models were used; one was EAU induced by one injection of purified bovine interphotoreceptor retinoid-binding protein (IRBP) with complete Freund's adjuvant in Lewis rat, and the other was an IRBP-induced autoimmune uveoretinitis that occurred spontaneously in nude (nu/nu) mice at 4 weeks of age reconstituted by the grafting of rat embryonic thymus (TG nude mouse). EAU develops when the IRBP-reactive lymphocytes in the regional lymph-nodes are activated. Activation begins when the T lymphocyte recognizes the peptide for the epitope bound to a major histocompatibility complex (MHC) molecule in the antigen-presenting cell by way of the T-cell receptor (TCR). In EAU, ten peptide residues p1182-1191 of the IRBP amino acid sequence, were revealed to be sufficiently capable of lymphocyte activation for EAU, and it was also shown that amino acid positions 1182W (tryptophane), 1185G (glycine), 1186V (valine) and 1188P (proline) of IRBP play important roles as the epitopes or agretopes in developing EAU. On the other hand, two amino acids of IRBP, amino acid positions 1182W (tryptophane) and 1194P (proline) were shown to be the agretopes inducing autoimmune uveoretinitis in the TG nude mouse. A study of the variable region of the TCR with a residual p1182-1194 specific T-cell line from the TG nude mouse revealed that as many as 96% utilized the T-cell receptor V beta 6 gene and that the peptide-MHC molecule complex was recognized by restricted receptors. Adhesion molecules such as ICAM-1 and LFA-1 were also found to play an important role as cofactors in activation of lymphocytes in the antigen-recognition process of EAU. Uveoretinitis seemed to result from an immune reaction in the eye occurring when the T lymphocyte arrives there, activating the immunological process. ICAM-1 and LFA-1 were also found to be involved in the infiltration process of inflammatory cells: our immunohistological examination revealed that ICAM-1 was present in the retinal pigment epithelium and epithelium of the ciliary body composing the blood-ocular barrier. In contrast, LFA-1 was expressed in the infiltrating cells. Finally, the tolerance of IRBP was discussed and it was experimentally demonstrated that the absence of IRBP-induced uveoretinitis in human beings and certain experimental animals resulted from endogenous IRBP serving as a tolerogen; we assumed that the breakdown of this self-tolerance would induce EAU due to thymic dysfunction or IRBP antigen injection.

Photoinactivation of T-cell function with psoralen and UVA radiation suppresses the induction of experimental murine graft-versus-host disease across major histocompatibility barriers.

Bone marrow transplantation is employed in the treatment of a number of hematologic and malignant diseases. A major complication is the induction of graft-versus-host disease. Whereas removal of T lymphocytes from the donor marrow effectively reduces the incidence of graft-versus-host disease, the incidence of graft failure often increases when T cells are depleted from the transplanted marrow. In the current study, photoinactivation of the donor cells with 8-methoxypsoralen coupled with exposure to long-wavelength ultraviolet radiation (PUVA therapy) was used to inactivate the response of the donor T cells against the host. PUVA therapy suppressed the ability of spleen cells to respond to alloantigen in the in vitro mixed lymphocyte reaction. The induction of acute graft-versus-host disease across complete major histocompatibility barriers in lethally X-irradiated mice was significantly suppressed after bone marrow transplantation with photoinactivated bone marrow cells. Long-term survivors demonstrated allogeneic reconstitution and partial restoration of T-cell function. Because PUVA therapy had no inhibitory effect on hematopoiesis, these data suggest that using phototherapy to inactivate the alloreactivity of T cells may provide an alternative to purging T cells from the donor marrow, thus suppressing both the incidence of graft-versus-host disease and the incidence of graft failure.