International Immunology Advance Access originally published online on January 17, 2008
International Immunology 2008 20(3):365-374; doi:10.1093/intimm/dxm148
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Antigen-dependent monophasic or recurrent autoimmune uveitis in rats
Section of Immunobiology, Department of Ophthalmology, Ludwig-Maximilians-University, Mathildenstrasse 8, 80336 Munich, Germany
Correspondence to: G. Wildner; E-mail: gerhild.wildner{at}med.uni-muenchen.de
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Abstract |
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Experimental autoimmune uveitis (EAU) in the Lewis rat has been regarded as an acute and monophasic disease. Uveitis can be induced by immunization with retinal soluble antigen (S-Ag), interphotoreceptor retinoid-binding protein (IRBP) or their peptide derivatives (PDSAg from S-Ag and R14 from IRBP) in CFA as well as by the transfer of activated, antigen-specific T cells. Previously, it has been shown that adoptively transferred, IRBP peptide-specific, but not S-Ag peptide-specific T cells can induce relapsing uveitis in rats. We observed spontaneous recurrences of intra-ocular inflammation even after immunization with R14 in CFA and were able to experimentally re-induce uveitis in rats previously immunized with autoantigen peptide in CFA. The efficiency of re-induction was dependent on the mode of pre-treatment [immunization or adoptive transfer (AT)] as well as on the antigen itself. Primary PDSAg-responses prevented subsequent re-induction of disease much more efficiently than primary R14-mediated EAU. In our model, the suppressive effect of CFA did not play a key role in preventing re-induction or spontaneous relapses. Furthermore, epitope spreading could not be demonstrated as a cause for recurrent inflammation. These data suggest that autoimmune responses with different antigen specificities could underlie similar clinical pictures while being differently regulated, which may help explain the variations in the disease courses in patients and the differential responses to therapeutic modalities.
Keywords: EAU, epitope spreading, experimental re-induction, IRBP, S-Ag
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Introduction |
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In contrast to the mouse model of experimental autoimmune uveitis (EAU) in B10.BR mice, in which relapsing EAU can be induced by decreasing the dose of immunizing antigen (1), EAU in rats is regarded as an acute, monophasic disease. No recurrences are generally observed after primary induction by active immunization or adoptive transfer (AT) of T cells specific for retinal soluble antigen (S-Ag) or one of its uveitogenic peptides. Recently, Shao et al. (2) showed that the adoptive transfer of uveitogenic T cells specific for a peptide from interphotoreceptor retinoid-binding protein (IRBP) [R16, amino acid (aa) 1177–1191] could cause multiple spontaneous recurrences of intra-ocular inflammation. We observed recurrences of disease also after immunization with an elongated form of R16, IRBP peptide R14 (aa 1169–1191), in addition to relapses after adoptive transfer of R14-specific T cells.
The induction of EAU in Lewis rats by active immunization with retinal antigens or their peptide derivatives in CFA was regarded as a means to prevent recurrences of the disease due to a suppressive effect of the Mycobacterium tuberculosis within the CFA (3). The mycobacteria-dependent induction of IFN-
is thought to provoke a general down-regulation of the immune response (4).
Nevertheless, uveitis in horses can be experimentally induced and also repeatedly re-induced by immunization with IRBP in CFA (5). In contrast to IRBP, retinal S-Ag is not a useful pathogen in horses (6). Here, we investigated the possibility to experimentally re-induce EAU after primary disease elicited with active immunization or adoptive T cell transfer. The comparison of two distinct autoantigen peptides and two means of disease induction, active immunization and T cell transfer, revealed striking differences between the T cell responses specific for S-Ag or IRBP peptide. In contrast to primary R14-specific disease, primary induction of EAU with specificity for S-Ag peptide PDSAg was followed by impaired re-induction. Differences in the regulation of PDSAg- and R14-mediated EAU have been previously described by our group, where the effect of the CCL5 mutant Met-RANTES was found to completely suppress uveitis induced by adoptive transfer of PDSAg-specific T cells (7). Here, we show differences in the regulation of re-induction of EAU mediated by PDSAg- and R14-specific immune responses.
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Antigen peptides
Custom peptides were purchased from Biotrend (Cologne, Germany). Peptides derived from the sequence of bovine S-Ag are PDSAg (aa 342–355), peptide M (bovine S-Ag aa 303–315), SAg281 (aa 281–296) and SAg286 (aa 286–297). Peptides from human IRBP are R14 (aa 1169–1191), R16 (IRBP aa 1177–1191), PDIRBP (aa 1174–1187), R4/R14 (aa1169–1180), R4T (aa 1163–1176), PI536 (aa 536–549), PI731 (aa 731–744) and PI1137 (aa 1137–1152). Ovalbumin (OVA) was purchased from Sigma (Deisenhofen, Germany), and purified protein derivative (PPD), tuberculin, was donated by Behring (now Sanofi-Aventis, Marburg, Germany). S-Ag was purified as described (8).
Animals
Male and female Lewis rats were bred in our own colony or purchased from Janvier (Le Genest St Isle, France), maintained in sterile isolators and used for experiments at the age of 6–8 weeks. They had unlimited access to rat chow and water. Animal experiments were approved by the Review Board of the Government of Oberbayern and conformed to the ARVO Statement on the Use of Animals in Ophthalmic and Vision Research.
Induction of EAU
Immunization.
Groups of four rats were immunized subcutaneously (s.c.) into both hind legs with a total volume of 200 µl emulsion containing 50 µg R14 or 15 µg PDSAg and CFA, fortified to a final concentration of 2.5 mg ml–1 with M. tuberculosis strain H37RA (BD, Heidelberg, Germany). For adoptive transfer, T-cell lines specific for R14 or PDSAg were established as described (9). A total of 2.5 x 106 antigen-activated, peptide-specific T cells were injected intra-peritoneally. Groups of rats for re-induction and the respective controls were age and sex matched.
Grading of EAU
The time course of disease was determined by daily examination of animals with an ophthalmoscope. Uveitis was graded clinically as follows: score 0, no signs of inflammation; 0.5, dilated iris vessels; 1, peripupillar infiltrates; 2, pupil covered with fibrin; 3, hypopyon and 4, hypopyon with hemorrhage. The average clinical score of all eyes is shown per group and day. For histological analysis, eyes from sacrificed animals were immediately snap frozen in Tissue Tec OCT compound (Paesel and Lorey, Frankfurt/Main, Germany) in methyl butane. Cryosections of rat eyes were immunohistochemically stained for CD4 (10) and graded as described (11).
Transfer of spleen and mesenteric lymph node cells from CFA-immunized rats
Lewis rats were immunized with an emulsion of PBS and 100 µl CFA; spleens were collected 4 weeks later. Single-cell suspensions of spleen cells were cultivated for 48 h in RPMI 1640 (PAA, Coelbe, Germany) with 5% FCS and 1 µg ml–1 ConA (BD), before 2 x 108 spleen cells were injected intra-peritoneally into naive recipient rats. The animals were subsequently immunized s.c. with either PDSAg-CFA or R14-CFA.
Proliferation of lymph node cells
Inguinal, popliteal and para-aortal lymph nodes were collected from rats either immediately after spontaneous relapses or 10 days after secondary immunization (5–6 days after second course of disease). Single-cell suspensions were cultivated at 5 x 105 per 200 µl RPMI 1640 (PAA) with 20 µg ml–1 antigens (PPD: 10 tuberculin U ml–1) and 2% rat serum (PAA). After 3 days of incubation, the cells were pulsed with 1 µCi [3H]thymidine per well (PerkinElmer, Rodgau, Germany) for 18 h before harvesting. Proliferation is given as stimulation index.
Statistics
Statistics were performed using Mann–Whitney U-test.
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Primary disease and spontaneous relapses of EAU
The onset of clinical disease induced by immunization with PDSAg-CFA was observed 2–3 days later as compared with R14-CFA immunization (Fig. 1), both settings presenting with similar anterior chamber inflammation. The individual courses of disease in single eyes were more variable in PDSAg-induced EAU as compared with the more synchronized inflammation of eyes in rats with R14-mediated disease. Similar observations were made for EAU induced by the adoptive transfer of T cells specific for these antigens (data not shown). The course of EAU after immunization with PDSAg or adoptive transfer of PDSAg-specific T cells was monophasic (Fig. 2A), whereas the transfer of R14-specific T cells (Fig. 2B) or immunization with R14 (Fig. 2C) induced recurrent episodes of inflammation. The recurrences varied in individual eyes and animals. The incidence of relapses of 19 R14-immunized rats after an extended observation period of 4–6 weeks after immunization was 63%. After adoptive transfer of T cells, the relapses occurred earlier than after immunization with R14-CFA.
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Re-induction of EAU
To investigate whether EAU can be re-induced experimentally, disease was induced by immunization with either R14-CFA or PDSAg-CFA or by adoptive transfer of T-cell lines specific for R14 (R14-AT) or PDSAg (PDSAg-AT), and then re-induced with all combinations (Table 1). PDSAg-CFA pre-immunization severely impeded further attempts at re-induction, whereas primary induction with R14-CFA allowed re-induction of mild inflammation. The incidences of affected animals did not strictly correlate with the significantly decreased disease scores. That is, re-induction after prior R14-CFA immunization resulted in average clinical scores of 1.1–1.2 (except secondary PDSAg-CFA immunization with an average score of 0.1) with incidences of 100% (secondary PDSAg-CFA: 36%). After primary PDSAg-CFA immunization, EAU average scores were 0.1–0.5 only, with incidences between 25% (secondary PDSAg-AT and R14-AT) and 50–62.5% (secondary PDSAg-CFA and R14-CFA, respectively).
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R14-specific secondary responses (immunization and adoptive transfer) were less diminished by preceding R14-CFA immunizations than the PDSAg responses after PDSAg-CFA immunization. After adoptive transfer of R14-specific cells, uveitis could be fully re-induced. Primary induction with PDSAg-AT resulted in reduced secondary disease scores (scores between 0.4 and 1.1), with incidences varying from 100% (scores 0.7 and 0.8) to 75 and 50% (scores 1.1 and 0.4 for re-induction with R14-CFA and PDSAg-CFA, Table 1). However, impairment of EAU re-induction by first induction with PDSAg-AT was less efficient than primary treatment with PDSAg-CFA.
Primary immunizations with CFA significantly suppressed EAU mediated by subsequent PDSAg-CFA immunization (P < 0.01), whereas secondary R14-CFA immunizations were not influenced, indicating a dual suppressive effect on PDSAg-specific immune responses: the unspecific suppression by M. tuberculosis within the CFA, and on the other hand an antigen-specific effect, not allowing efficient secondary disease induction following a prior PDSAg-specific response.
Histology of rat eyes
The clinical uveitis score correlates with maximal inflammation in the anterior chamber, and the histological score decribes final retinal destruction. Severe inflammation in the anterior chamber is not necessarily followed by severe retinal destruction, as shown in Fig. 3A. While PDSAg-mediated EAU usually leads to severe anterior inflammation and retinal destruction, severe anterior inflammation mediated by R14 is often accompanied by a slightly lower histological score (Fig. 3B). R14-specific disease mainly resulted in destruction of photoreceptors (histological score 1–2), whereas retinas of PDSAg-mediated EAU often showed lesions extending to the inner nuclear layer (score 3). The clinical score of rats immunized with PBS–CFA prior to EAU induction by R14-CFA immunization (Fig. 3A) was as high as of the previously untreated control groups (score 2, Fig. 3B), but the histology revealed only little retinal destruction. In contrast, PDSAg-CFA immunization after previous treatment with CFA resulted in only mild anterior chamber inflammation and minor retinal destruction (Fig. 3A). So far we cannot explain why CFA protects from retinal destruction but still allows repeated episodes of anterior inflammation.
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In order to further investigate the effect of CFA, we transferred splenocytes from naive rats or animals previously immunized with CFA. Compared with the group transferred with ‘untreated’ splenocytes, rats receiving CFA-primed cells showed slightly diminished infiltration of inflammatory cells after PDSAg immunization (Fig. 3C), which had no effect on retinal destruction as detected by histology (Fig. 3D). The group that was only immunized with PDSAg-CFA developed a more severe disease, as observed by clinical examination (Fig. 3C) as well as by histology (Fig. 3D). No such effects could be obtained by subsequent R14-CFA immunization.
Histology of eyes from rats treated to re-induce EAU showed the final retinal destruction after two episodes of intra-ocular inflammation (Fig. 4A–D). The histology always revealed severe retinal destruction when primary disease was PDSAg mediated, irrespective of the secondary treatment (Fig. 4A–D), suggesting that most of the retinal destruction happened during the primary course of disease, which is supported by the findings shown in Fig. 3B. There was more retinal destruction after PDSAg than after R14 immunization. The histological scores in re-induced eyes (Fig. 4A–D) were slightly higher (3–4) than in control eyes with a single course of disease (mean scores < 3, Fig. 3B), indicating an additional, secondary wave of retinal destruction. When primary disease was R14-mediated, the final histological scores remained low, between 1 and 2 (Fig. 4A–D), and only when the disease was re-induced with PDSAg-specific T cells (Fig. 4D), retinal destruction increased, resulting in a histological score of 3. When disease was first induced with R14-CFA and then re-induced by transfer of PDSAg-specific T cells (Fig. 4C), a strong correlation of clinic and histology was observed: this combination resulted in decreased anterior chamber inflammation as well as decreased retinal destruction. Although PBS–CFA pre-immunization had no effect on EAU induced by subsequent transfer of PDSAg-specific T cells, prior immunization of CFA with retinal antigen (R14, PDSAg) suppressed the ability of the transferred cells to induce inflammation (Table 1) or to destroy the retina (Fig. 4D).
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Comparison of clinical diseases in single eyes during primary and secondary disease
The maximal clinical disease of each eye during the first course of EAU and the re-challenge is shown in Fig. 5. Most, but not all eyes showed decreased inflammation during the secondary course of disease. Some eyes even had increased (Fig. 5I–L and N) or similar inflammation (Fig. 5A, C, D, I–L and P) during the second attack. Most eyes with high secondary inflammation (scores 2–3) had only mild primary disease (score 1), but some also showed a score of 2 (Fig. 5D, I, K, L and P). Of those rats primary immunized with peptide in CFA, only few eyes had increased or similar clinical score during the secondary course of disease (Fig. 5A, C and D).
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Time course of re-induced disease
When disease was induced by adoptive transfer of PDSAg-specific T cells and then re-induced (Fig. 6A–D), the onset of secondary, very mild clinical disease was concomitant with EAU of the non-pre-treated control rats (Fig. 6B–D). Only in the group that was re-induced by PDSAg-CFA immunization, the onset of secondary low-grade inflammation preceded that of the control group of 5 days (Fig. 6A). In those rats, which were primarily induced by adoptive transfer of R14-specific T cells (Fig. 6E–H), the course of the re-induced clinical disease was comparable with the primary disease course with respect to duration and intensity (Fig. 6F–H), but with a slightly earlier onset of 1–2 days compared with the controls. Only when the rats were re-induced by PDSAg-CFA immunization (Fig. 6E), the intra-ocular inflammation was milder than during the primary course of EAU.
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Antigen specificity of T-cell responses in vitro
Rats were immunized with R14-CFA and draining lymph nodes collected immediately after spontaneous relapses (Fig. 7A and B) or after recurrences induced by re-immunization with R14-CFA (Fig. 7E and F). To prove whether immunization with CFA and an antigen unrelated with uveitis can induce a relapse, we secondary immunized with OVA–CFA (Fig. 7C and D). Proliferation was tested in response to a variety of peptides derived from IRBP or S-Ag, S-Ag protein, OVA and PPD as a representative antigen of M. tuberculosis from CFA. Of 12 rats immunized with R14-CFA, two animals had spontaneous relapses after 24 days (both eyes, Fig. 7A) or after 19 (left eye) and 23 days (right eye, Fig. 7B), respectively. OVA–CFA immunization did not cause relapses, whereas after secondary immunization with R14-CFA, all animals had recurrences of inflammation between days 4 and 6 after second R14-CFA injection. The lymphocytes from one of the two spontaneously relapsing rats displayed intramolecular epitope spreading from R14/R16 to R4/R14 and intermolecular spreading to S-Ag peptide PDSAg (Fig. 7A), while the other rat (with independent relapses of both eyes) only showed weak lymph node cell proliferation in response to peptides R14 and R16, the latter representing the main T-cell epitope of peptide R14 (Fig. 7B).
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Lymphocytes from rats that were re-immunized with R14-CFA (Fig. 7E and F) had recurrent disease, but only responded to R14 and R16 and to none of the other tested antigens, indicating that the re-induced EAU was mediated R14 specifically. However, we cannot exclude any immune response to an epitope that was not tested. Their pattern of antigen recognition was similar with that of the control rats that were only once immunized with R14-CFA and lymph nodes collected 11 days later (Fig. 7G and H). The only difference was the higher response to PPD in re-immunized rats. Those rats that were re-immunized with OVA–CFA to provoke relapses by an unspecific immunologic stress as provided by the CFA did not experience any relapses (Fig. 7C and D). Their lymph node cell proliferations revealed specificity for R14 and R16 from the primary R14 immunization, OVA from secondary immunization and for PPD as antigen from CFA.
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Discussion |
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The rat model of EAU is well established with two different antigens from the photoreceptor layer: IRBP, an extracellular transport protein, and S-Ag, an intracellular antigen and the major protein of the dry mass of photoreceptors. Both proteins and their well-defined peptides are potent immunogens upon immunization in CFA emulsions, and Th1 cell lines with specificity for these antigens can efficiently induce disease after transfer to naive rats.
For a long time, EAU induced with either antigen was thought to result in similar diseases, although a preference for anterior inflammation in R14-mediated disease and more posterior involvement caused by PDSAg-specific immunity was observed. In addition, R14-induced EAU has an earlier onset than PDSAg-mediated disease, and after adoptive transfer of T cells with either peptide specificity, clinical signs of disease appear earlier than after immunization. Here in this model, we describe spontaneous relapses, which occur earlier after adoptive transfer than after active immunization. This could be explained by the fact that immunization with antigen in CFA results in a depot of antigen remaining for an extended period of time, which might redirect antigen-specific T cells to the draining lymph nodes after induction of intra-ocular inflammation and thus probably delaying their return to the eye. Adoptively transferred T cells follow the conventional homing to lymphoid organs after EAU induction and have no secondary source of their specific antigen except within the eye.
Irrespective of the mode of induction, we observed differences in the retinal infiltration of leucocytes (7). While in PDSAg-induced EAU T cells and inflammatory cells preferentially infiltrate the eye via the choroid and the retinal pigment epithelium with destruction of the latter, in R14-induced EAU the infiltration is mainly via the retinal vessels, leaving the RPE intact even when the photoreceptors are destroyed.
Differences in the regulation of PDSAg- and R14-mediated EAU have been previously observed. Met-RANTES, a CCR1/CCR5 antagonist, completely blocks EAU induced by adoptive transfer of PDSAg-, but not by R14-specific T cells, although T-cell lines specific for either peptide expressed similar amounts of CCR1 and CCR5. We had also tested the cytokine secretion of T-cell lines with specificity for R14 and PDSAg and found that both display a Th1 pattern. Although gene array analyses (Wildner et al., unpublished data) revealed that mRNA levels were similar in both types of T-cell lines, R14-specific T cells secrete up to 10-fold more IFN- and tumor necrosis factor (TNF)-
than PDSAg-specific T-cell lines. Both cytokines were also shown to be associated with relapsing experimental autoimmune encephalomyelitis (12, 13).
The difference in disease susceptibility might be limited to a specific genotype (here, Lewis strain), which we did not further investigate, because the respective peptides were not even immunogenic in MHC-recombinant Lewis rats Lew 1.N and Lew 1.W (generous gifts from K. Wonigeit, Hannover, Germany). Neither Lew 1.N (MHC locus of BN rats) nor Lew 1.W (MHC locus of Wistar Furth rats) was able to respond to these peptides (data not shown) due to the lack of suitable MHC class II presentation.
Rat EAU was regarded as an acute, monophasic disease irrespective of the antigen specificity of the autoimmune response. Nevertheless, it was recently described that relapsing disease can be induced after adoptive transfer of IRBP peptide R16-specific T cells, but not after immunization with R16 in CFA (14). We could observe spontaneous relapses following immunization with R14-CFA, an elongated form of R16, as well as after adoptive transfer of R14-specific T cells. In our hands, the spontaneous relapses after adoptive transfer did not appear regularly, which was probably due to the low number of transferred cells (14).
Pre-treatment of rats by immunization with PBS–CFA resulted in impaired induction of EAU by immunization with PDSAg-CFA, but not R14-CFA, suggesting a CFA-mediated difference in the regulation of R14- and PDSAg-specific immune responses. To further address this phenomenon, we transferred splenocytes from CFA-immunized rats to test for cellular mechanisms of regulation in the group receiving CFA-challenged spleen cells. While no difference in R14-induced EAU was observed, irrespective of prior spleen cell transfer or not, we found a general mild suppression of PDSAg-induced EAU after spleen cell transfer, but no significant difference between unprimed or CFA-challenged spleen cells. This could point to a natural PDSAg-specific regulatory cell population in the rat spleen. We suspect splenic macrophages, which can suppress immune responses and even autoimmune diseases by nitric oxide (NO) production (15). PDSAg-specific T cells, which secrete lower levels of Th1 cytokines compared with R14-specific T lymphocytes, might be suppressed by the transfer of macrophage-containing splenocytes.
The immunosuppressive effect of NO secretion by macrophages can be enhanced by M. tuberculosis, which is a major component of CFA. Mycobacterium tuberculosis is a strong inducer of IFN- and promotes the EAU-inducing Th1 as well as NO synthesis. On the other hand, M. tuberculosis suppresses further Th1 responses (4, 16) by enhancing the expression of NO synthase (17), explaining the suppressive effect of CFA pre-immunization on PDSAg-CFA-induced EAU. R14-specific T cells with their increased secretion of IFN- and TNF- could probably overrun this suppression. While Shao et al. (14) induced relapses only after adoptive transfer, we observed recurrent EAU even after immunization with R14 in CFA, using lower concentrations of M. tuberculosis than Shao et al.
On the other hand, NO plays an important role in retinal destruction. It has been shown that the addition of S-Ag protein induces more NO than IRBP in a macrophage line or peritoneal macrophages (18). S-Ag peptide PDSAg-specific immune reactions result in photoreceptor destruction with enhanced release of S-Ag, which might have a direct effect on augmenting NO production in infiltrating macrophages. The increased destruction of the photoreceptors, which are the source of both autoantigens, S-Ag and IRBP, could explain the impaired re-induction after primary PDSAg-mediated disease. Rats with R14-CFA-induced EAU had usually less severe tissue destruction represented by lower histological scores. We know that efficient induction of intra-ocular inflammation needs only invasion of few antigen-specific effector T cells, as demonstrated by the use of GFP+ uveitogenic T cells (19), while the majority of infiltrating cells in rat EAU are monocytes, macrophages and T cells of other specificities probably unrelated with uveitis (7). Eyes with high primary inflammatory score tend to be more resistant to the induction of a secondary course of disease; however, even eyes with severe destructive uveitis mediated by PDSAg-specific T-cell responses experienced secondary inflammation. Therefore, we favor regulatory phenomena to explain the prevention of secondary episodes of inflammation rather than loss of the respective autoantigens by partial tissue destruction. This is supported by the fact that even primary low-grade PDSAg-mediated EAU led to decreased secondary disease in the respective eye, whereas severe R14-mediated inflammation could be followed by intense secondary inflammation. However, so far we could not yet define antigen-specific regulatory T cells that would prevent recurrences of disease.
The appearance of spontaneous relapses could be explained by epitope spreading, a phenomenon observed and described for autoimmune disease models. We have even described intra- and inter-molecular epitope spreading during the course of multiple induced recurrences of uveitis in experimental horses (5).
To verify epitope spreading as a reason for recurrences and easy re-induction after primary R14-CFA induction, we investigated the in vitro proliferative response of lymph node cells from immunized rats. In only one of the spontaneous relapse cases, we detected reactivity to another epitope from IRBP and to S-Ag peptide PDSAg, indicating that epitope spreading may be an unrelated epiphenomenon. OVA- and R14-re-immunized animals had only responses to R14 (and its major epitope R16) and OVA, respectively. Epitope spreading is either a rare event in our model of EAU, or the immune response had extended to epitopes not provided by our selection of peptides used for in vitro assays (20, 21).
Our data point to the fact that acute, monophasic and chronic relapsing disease can occur within the same strain of experimental animals, depending on the antigen rather than on generalized regulatory mechanisms. R14- as well as PDSAg-specific effector cells target the same organ and even the same tissue and nevertheless behave differently with respect to tissue destruction and regulation. Transferred to the human situation, where we do not know the exact antigen specificities of the autoimmune response or the numbers of the recognized antigens, we might have several immune phenomena with different reactions and regulations interfering with each other in the same patient, especially when we consider epitope spreading as a potential cause for relapsing or chronic disease. This could explain the changing course of disease in patients, when single episodes of disease become relapsing or chronic progressive. Furthermore, clinically similar apparent diseases could be maintained by different immune responses to diverse antigens and thus be differentially regulated.
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Deutsche Forschungsgemeinschaft (SFB 571).
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Acknowledgements |
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We thank Isabella Rädler-Angeli for excellent technical assistance, Stephan R. Thurau for critically reviewing the manuscript and our colleagues from the Department of Neuroimmunology, Max-Planck-Institute of Neurobiology, Martinsried, Germany for lending us a centrifuge to enable the continuation of these experiments.
Funding to pay the Open Access publication charges for this article was provided by Deutsche Forschungsgemeinschaft SFB 571.
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Abbreviations |
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| aa, amino acid |
| ARVO, Association for Research in Vision and Ophthalmology |
| AT, adoptive transfer |
| EAU, experimental autoimmune uveitis |
| GFP, green fluorescent protein |
| IRBP, interphotoreceptor retinoid-binding protein |
| NO, nitric oxide |
| OVA, ovalbumin |
| PPD, purified protein derivative |
| S-Ag, retinal soluble antigen |
| s.c., subcutaneously |
| TNF, tumor necrosis factor |
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Notes |
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Transmitting editor: T. Hünig
Received 22 May 2007, accepted 13 December 2007.
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References |
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