Staphylococcal enterotoxin enhances the activation of rat encephalitogenic T cells by myelin basic protein

Minimally activated CD8 autoreactive T cells specific for IRBP express a high level of Foxp3 and are functionally suppressive

PURPOSE

Results in previous reports have demonstrated that immunization of the EAU-prone B6 mouse activates both CD4 and CD8 IRBP-specific T cells. The purpose of this study was to investigate structural and functional differences between CD4 and CD8 autoreactive T cells activated by the uveitogenic peptide.

METHODS

Purified CD4 and CD8 isolated from B6 mice immunized with an uveitogenic peptide, interphotoreceptor retinoid-binding protein (IRBP)1-20, were stimulated in vitro with various doses of immunizing peptide. The activated T cells were determined for cytokine production, expression of Foxp3, and suppressor activity.

RESULTS

CD4 autoreactive T cells underwent full activation when stimulated with high or medium concentrations of immunizing peptide, whereas a high dose of antigenic peptide resulted in only modest activation of CD8 autoreactive T cells. When stimulated by a low dose (<0.1 microg/mL) of antigen or by of a high dose of antigen and a small amount of TGF-beta1, the minimally activated CD8 T cells expressed a high level of Foxp3 and gained suppressor function.

CONCLUSIONS

Minimally activated CD8 autoreactive T cells can be functionally suppressive and may neutralize the tissue-damaging effect of the CD4 autoreactive T cells.

CpG-containing oligodeoxynucleotide 1826 converts the weak uveitogenic rat interphotoreceptor retinoid-binding protein peptide 1181-1191 into a strong uveitogen

Aberrant activation of autoreactive T cells is one of the major causes of autoimmune disease. Autoantigens are sequestered and in many cases weak immunogens. For example, in experimental autoimmune uveitis, immunization of naive rats with autologous interphotoreceptor retinoid-binding protein (IRBP) fails to induce intraocular inflammation or a strong T cell response, whereas bovine IRBP is a strong inducer of experimental autoimmune uveitis. Such observations challenge the view that the autoantigen alone is responsible for the development of autoimmunity. Here, we demonstrate that autologous rat IRBP is converted to a strong immunogen in the presence of a small dose of CpG-containing oligodeoxynucleotides. Our results indicate that specific CpG-containing oligodeoxynucleotides may play an important role in the activation and expansion of autoreactive T cells in vivo, leading to autoimmune disease.

Effect of staphylococcal enterotoxin B injection on the development of experimental autoimmune encephalomyelitis: influence of cytokine and inducible nitric oxide synthase production

Possible mechanisms involved in the protective effect of staphylococcal enterotoxin B (SEB) injection on the subsequent development of experimental autoimmune encephalomyelitis (EAE) were investigated. Only partial clonal deletion and anergy of Vbeta8 + T-lymphocytes were documented after myelin basic protein immunization in SEB injected mice. Brain permeability was not influenced. Within the brain or during in vitro rechallenge assays SEB protected mice produced significantly more IL-10, IL-4, TNF-alpha and iNOS. It is suggested that the immune deviating effect of SEB may be involved in its EAE protective effect.

Multiple sclerosis, dental caries and fillings: a case-control study

OBJECTIVES

To investigate the association between multiple sclerosis, dental caries, amalgam fillings, body mercury and lead.

DESIGN

Matched case-control study.

SETTING

Leicestershire in the years 1989-1990.

SUBJECTS

Thirty-nine females with multiple sclerosis (of recent onset) were matched with 62 controls for age, sex and general practitioner.

METHODS

Home interview of cases and controls within which there was an assessment of the DMFT index and blood and urine mercury and lead levels.

RESULTS

The odds of being a MS case increased multiplicatively by 1.09 (95% CI 1.00, 1.18) for every additional unit of DMFT index of dental caries. This represents an odds ratio of 1.213 or a 21% increase in risk of MS in relation to dental caries in this population. There was no difference between cases and controls in the number of amalgam fillings or in body mercury or lead levels. There was a significant correlation between body mercury levels and the number of teeth filled with amalgam (controls: r = +0.430, P = 0.006, cases: r = +0.596, P = 0.001).

CONCLUSION

There was evidence of excess dental caries among MS cases compared with the controls. This finding supports the strong geographical correlation between the two diseases. A further study of this association is recommended.

Protection from experimental autoimmune encephalomyelitis (EAE): non-depleting anti-CD4 mAb treatment induces peripheral T-cell tolerance to MBP in PL/J mice

Following pre-treatment with a non-depleting anti-CD4 mAb (H129.19) that produces long-lasting receptor saturation, PL/J mice were fully protected from experimental auto-immune encephalomyelitis (EAE) induced by injection of myelin basic protein (MBP). These mice did not develop EAE following MBP re-challenge 5-10 weeks later when the CD4+ cells were no longer coated by the mAb and their lymph node cells were specifically unresponsive to MBP stimulation in vitro. Moreover, superantigen staphylococcal enterotoxin B (SEB) inoculation, which re-induces EAE in MBP immunized mice, failed to activate encephalitogenic T-cells in anti-CD4 + MBP treated mice, even after MBP re-challenge, indicating that tolerance in the peripheral T-cell compartment was achieved. However, MBP re-challenge 16 weeks later, but not SEB, produced an acute episode of EAE in these mice, while it failed to induce disease in a parallel group of adult thymectomized mice. These results indicate that no memory of the first priming exists at this time and that new MBP-specific T-cell precursors are peripheralized and produce EAE after MBP recognition.

Environmental risk factors in MS: a case-control study in Moscow

Environmental influences operating as possible risk factors in MS were studied in Moscow. The study included 155 MS patients from the Neurology Departments and the outpatient clinics of the First City Hospital of Moscow and 155 controls matched for sex, age in 5-year intervals, nationality, and origin (Moscow vs. non Moscow). 72.3% of controls were recruited among patients from the same hospital as the cases. The remaining controls were volunteers from the hospital staff or medical students. Exposures before age 15 were of special interest. MS patients reported a higher frequency of: 1) tonsillitis; 2) allergic reactions age 15; 3) head trauma below age 16; 4) a predominant meat vs. vegetable diet during childhood. Stratified analysis and logistic regression pointed to "meat predominance" as the most significant risk factor. Other associations were confounded by the respondents' occupations/education.

Multiple sclerosis: sunlight, diet, immunology and aetiology

Multiple sclerosis is more common in temperate latitudes, and migration studies indicate the involvement of an aetiological environmental factor in pre-pubertal life; the precise nature of this factor has never been identified and may perhaps have been overlooked. Here we suggest a simple explanation for the latitude gradient of multiple sclerosis, i.e. that it can be explained by the immunosuppressant effects of sunlight mediated via suppression of the secretion of the immunostimulatory neurohormone melatonin from the pineal gland. The effects of dietary fatty acids in multiple sclerosis also indicate the involvement of anti-inflammatory eicosanoids in its pathogenesis. We further suggest that the exceptions to the latitude gradient (e.g. Japan), which have previously been attributed to genetic factors, may in fact have a dietary basis. Since sunlight also influences the metabolism of fatty acids in the retina, it may also influence the development of retrobulbar optic neuritis-a common antecedent of multiple sclerosis. We suggest a re-examination of the epidemiology of multiple sclerosis based on an understanding of the immunological consequences of illumination of the retina by sunlight.

Heterogeneity of rat encephalitogenic T cells elicited by variants of the myelin basic protein (68-86) peptide

By immunizing Lewis rats with myelin basic protein (MBP) peptide variants derived from the major encephalitogenic epitope of guinea pig (MBP(68-88) and then isolating encephalitogenic T cells from these animals, we demonstrated that the variant peptides do not elicit the same encephalitogenic T cell subsets as those induced by the wild-type peptide or by intact MBP. Rather, the pathogenic T cells differed in clonal composition as reflected by their heterogeneous responses to a panel of variant peptides and by their T cell receptor usage. Thus, molecules mimicking the MBP(68-88) autoantigen can elicit pathogenic T cell subsets without necessarily cross-reacting with T cells specific for the original autoantigen. This suggests that a more clonally diverse group of pathogenic T cells might be involved in EAE than has been apparent from studies with intact MBP or its unaltered peptides.

The clonal composition of myelin basic protein-reactive encephalitogenic T cell populations is influenced both by the structure of relevant antigens and the nature of antigen-presenting cells

Studies of experimental autoimmune encephalomyelitis (EAE) in rodents have revealed that encephalitogenic T cell lines reactive with myelin basic protein (BP) are frequently dominated by clones expressing a restricted T cell receptor repertoire. Using the rat EAE model, we have begun to examine the basis for clonal dominance within BP-reactive T cell lines. We find that variations introduced into the standard protocol of periodic antigen stimulation produce marked shifts in the representation of different clones within encephalitogenic T cell populations. For example, altering the source of antigen-presenting cells (APC), while holding antigen (BP) constant, and substituting BP from guinea pig (GPBP) for that of the rat antigen (RBP) with constant APC, both cause shifts in the composition of the dominant clones within BP-reactive T cell lines. Our results suggest that: (i) adherence to an invariant protocol of antigen challenge may lead to an underestimation of the diversity of BP-reactive encephalitogenic T cell populations; and (ii) the minor structural differences between GPBP and RBP not only cause the weak immunogenicity of RBP but also result in the alteration of different T cell subsets. These observations indicate that apparent restrictions upon the repertoire of autoimmune T cells should be interpreted with caution when such cells are elicited by immunization with foreign antigens.