The beta 2-adrenergic agonist salbutamol potentiates oral induction of tolerance, suppressing adjuvant arthritis and antigen-specific immunity

Therapeutic protocols for treating autoimmune diseases by feeding autoantigens during the disease process have not been very successful to date. In vitro it has been shown that beta-adrenergic agonists inhibit pro-inflammatory cytokine production and up-regulate anti-inflammatory cytokine production. We hypothesized that the protective effect of oral administration of Ag would be enhanced by oral coadministration of the beta(2)-adrenergic agonist salbutamol. Here we demonstrate that oral administration of salbutamol in combination with the Ag mycobacterial 65-kDa heat shock protein increased the efficacy of disease-suppressive tolerance induction in rat adjuvant arthritis. To study the mechanism of salbutamol in more detail, we also tested oral administration of salbutamol in an OVA tolerance model in BALB/c mice. Oral coadministration of OVA/salbutamol after immunization with OVA efficiently suppressed both cellular and humoral responses to OVA. Coadministration of salbutamol was associated with an immediate increase in IL-10, TGF-beta, and IL-1R antagonist in the intestine. The tolerizing effect of salbutamol/OVA was maintained for at least 12 wk. At this time point IFN-gamma production in Ag-stimulated splenocytes was increased in the OVA/salbutamol-treated animals. In conclusion, salbutamol can be of great clinical benefit for the treatment of autoimmune diseases by promoting oral tolerance induction.

Immunomodulatory effects of antigen-pulsed macrophages in a murine model of allergic asthma

Macrophages (Mphi) play an unique role in the activation and regulation of T cells through their ability to modulate specific costimulatory and cytokine signals. Here we investigated the immunomodulatory effects of allergen presentation by Mphi in a murine model of allergic asthma. Purified peritoneal Mphi were pulsed with ovalbumin (OVA) (OVA-Mphi), or the immunodominant epitope OVA(323-339) (OVA(323-339)-Mphi), and characterized for cell surface markers, cytokine production, and antigen-presenting capacity toward OVA(323-339)-specific DO11.10 T cells. Antigen-pulsed Mphi were injected (intravenously) in OVA-sensitized Balb/c mice that were repeatedly challenged with OVA or saline aerosol. Administration of OVA-Mphi inhibited airway eosinophilia and hyperresponsiveness to methacholine concomitant with a reduced interleukin (IL)-4 and IL-5 production by T cells upon OVA stimulation in vitro. Interestingly, OVA-induced IL-10 levels remained unchanged, whereas interferon-gamma could not be detected. In contrast to OVA-Mphi, OVA(323-339)-Mphi administration had no effects on these asthma manifestations. Additional in vitro studies demonstrated that OVA-Mphi, but not OVA(323-339)-Mphi, produced high levels of IL-10 upon interaction with the DO11.10 T cells. This IL-10 production by the OVA-Mphi was dependent on MHC-TCR and CD86-CD28, but not CD80-CD28 or CD40-CD154 interactions. Our data suggest that IL-10 production by allergen presenting Mphi plays a crucial role in successful immunotherapy.

Progressive bovine paratuberculosis is associated with local loss of CD4(+) T cells, increased frequency of gamma delta T cells, and related changes in T-cell function

Bovine paratuberculosis is caused by the infection of young calves with Mycobacterium avium subsp. paratuberculosis, resulting in a chronic granulomatous infection of predominantly the ileum. After an incubation period of 2 to 5 years, the disease becomes progressive in some of the chronically infected, but asymptomatic cows. This results in a protein-losing enteropathy that will ultimately be fatal. A loss of cell-mediated immune responses in symptomatic animals has been described, but no information is available concerning immune reactivity in the intestine. We sought to investigate putative disease status-associated lymphocyte subset distributions and antigen-specific functional characteristics of mononuclear cells isolated from blood, gut-associated lymphoid tissue, and the intestinal walls of 22 cows in different stages of disease and in control animals. The results demonstrated a significant decrease in CD4(+) T-cell frequency and a significant increase in TcR1-N12(+) gamma delta T-cell frequency in ileum lamina propria lymphocytes of symptomatic animals compared to the asymptomatic shedders. Immunohistology revealed that there was also an absolute decrease in the number of CD4(+) T cells in sections of the lesional ileum. Our findings also indicated that both peripheral and intestinal cell-mediated responses are decreased in symptomatic animals compared to asymptomatic animals. We conclude that the decrease in cell-mediated responses is likely related to a loss of antigen-specific CD4(+) T cells, which is most prominent in the lesional ileum from symptomatic animals, thus contributing to the progressive nature of bovine paratuberculosis.

Inhibition of adjuvant-induced arthritis by interleukin-10-driven regulatory cells induced via nasal administration of a peptide analog of an arthritis-related heat-shock protein 60 T cell epitope

OBJECTIVE

To prevent and treat experimental arthritis via nasal administration of an altered peptide ligand (APL) from the major arthritogenic epitope in adjuvant-induced arthritis (AIA) and to explore the mechanisms involved.

METHODS

Peptides were administered nasally before and after induction of arthritis. Splenocytes and lymph node cells draining both the site of inflammation and the site of tolerance induction were used for cell transfer and were studied for antigen-specific T cell characteristics. In addition, attempts were made to stop T cell tolerance in vitro, using anticytokine antibodies.

RESULTS

Nasal administration of a modulatory APL of the heat-shock protein 60 (Hsp60) 180-188 T cell epitope, alanine 183, had a suppressive effect in AIA that far exceeded that of the wild-type epitope. In addition to its effectiveness in preventing AIA, alanine 183 may be effective in the treatment of ongoing AIA. The protective effect of alanine 183 can be passively transferred using activated splenocytes. Nasal administration of alanine 183 did not lead to detectable T cell proliferation or interleukin-2 (IL-2) production in mandibular lymph node cells, while transforming growth factor beta (TGF beta), IL-10, and IL-4 were readily produced. Likewise, after nasally induced tolerance, followed by induction of arthritis, inguinal lymph node cells produced IL-4, TGF beta, and IL-10. After neutralizing in vitro the individual cytokines with anticytokine antibodies, only blocking of IL-10 production led to reversal of tolerance, at the site of tolerance induction and the site of inflammation.

CONCLUSION

Nasal administration of an APL of Hsp60 180-188 induces highly effective protection against AIA through generation of regulatory cells that produce IL-4, TGF beta, and IL-10, whereas the induced tolerance is driven mainly by production of IL-10.

Searching for the cartilage-associated mimicry epitope in adjuvant arthritis

Adjuvant arthritis (AA) is a T cell mediated disease which can be induced in genetically susceptible rats by immunization with heat-killed Mycobacterium tuberculosis (Mt) suspended in incomplete Freund's adjuvant. The critical mycobacterial T cell epitope for the induction of AA was previously identified as residues 178-186 of the mycobacterial 65 kDa heat shock protein (Mt. hsp65(178-186)). It was suggested that the development of AA was due to molecular mimicry between a mycobacterial epitope and a cartilage-associated self-antigen. However, until now such cartilage-associated mimicry epitope has not been identified. In this study we designed a computer search profile to predict mimicry self-epitopes, and investigated whether one or more of these self-epitopes could serve as mimicry epitopes in AA. Although several of these self-epitopes were recognized by arthritogenic T cells, no cross-reactivity was found between T cells specific for these self-epitopes and Mt. hsp65(178-186) specific T cells.

Cross-reactive mycobacterial and self hsp60 epitope recognition in I-A(g7) expressing NOD, NOD-asp and Biozzi AB/H mice

The highly conserved 60 kD endogenous heat shock protein (hsp60) has been suggested to be a target for T cell recognition in autoimmune diseases such as type I diabetes. We previously reported cross-recognition of both mycobacterial hsp60 (Mt60) and self hsp60 (m60) by Mt60 immunized NOD mice. To identify the epitopes involved, we generated T cell lines against m60 or its mycobacterial counterpart and tested these lines for recognition of complete sets of overlapping peptides spanning either hsp60 sequence. T cell lines responded to identical regions in the hsp60 proteins, regardless of their degree of conservation or I-A(g7) binding-affinity. Additionally, we determined whether a protective genetic background would affect the presence of hsp60 cross-reactive T cells in the peripheral repertoire by comparing epitope recognition in I-A(g7) expressing NOD, NOD-asp and Biozzi AB/H mice. Two out of five immunodominant murine peptides were able to induce proliferation in NOD and NOD-asp Mt60 T cell lines, but not in Biozzi AB/H T cell lines. Our results point out that Mt60 immunization not necessarily leads to proliferative T cells responding to endogenous hsp60 peptides in the context of diabetes-predisposing I-A(g7). Moreover, the capacity of T cells to respond to self hsp60 is not influenced by the presence of protective I-A(g7asp). Yet, proliferation of hsp60 autoreactive T cells is solely measured in combination with insulitis and as such serves as a surrogate marker for islet inflammation.

Successful immunotherapy with matrix metalloproteinase-derived peptides in adjuvant arthritis depends on the timing of peptide administration

We have recently found that matrix metalloproteinases (MMPs) are targets for T-cell and B-cell reactivity in experimental arthritis. In the present article, we investigate whether modulation of MMP-specific T-cell responses could influence the course of adjuvant arthritis (AA). Lewis rats were treated nasally with MMP peptides prior to or after AA induction. Administration of the MMP-10 or the MMP-16 peptide prior to AA induction reduced the arthritic symptoms. In contrast, administration of the MMP-10 peptide after AA induction aggravated the arthritic symptoms. The present study shows the possible usefulness of MMP peptides for immunotherapy. However, a clear understanding of proper timing of peptide administration is crucial for the development of such therapies.

Dose-Dependent Induction of Distinct Anergic Phenotypes: Multiple Levels of T Cell Anergy

T cell anergy has been proposed as one of the mechanisms underlying peripheral T cell tolerance. In recent years, the functional relevance of T cell anergy has been studied extensively in vitro and in vivo, using different species, cell systems, and ways to induce anergy. Although these studies concurred about the induction of unresponsiveness, conflicting findings were obtained with respect to the function of anergic T cells and to the persistence of T cell anergy. In the present study, T cell anergy was induced through T-T presentation of the specific Ag by rat MHC class II+ T cells in the absence of professional APC. We show that, depending on the Ag dose with which T cells were incubated, distinct anergic phenotypes were induced. Incubation of T cell clones with a low (suboptimal) Ag dose induced hyporesponsiveness. Incubation with a higher (optimal) Ag dose induced an anergic state capable of exerting immunoregulatory effects. Incubation with a high (supraoptimal) Ag dose led to an anergic suppressive phenotype that was persistent and was not reversed by APC, Ag, and rIL-2. These findings demonstrate that T cell anergy is not confined to a single state of functional inactivation. Instead, multiple levels of T cell anergy exist. Thus, anergic T cells can contribute to the regulation of the immune response either in a persistent and active manner or in a passive manner, depending on their level of T cell anergy.