Aberrant production of soluble costimulatory molecules CTLA-4, CD28, CD80 and CD86 in patients with systemic lupus erythematosus
C. K. Wong,
L. C. W. Lit,
L. S. Tam1,
E. K. Li1 and
C. W. K. Lam
Department of Chemical Pathology and 1 Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong.
Correspondence to: C. W. K. Lam, Department of Chemical Pathology, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong. E-mail: waikeilam{at}cuhk.edu.hk
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Abstract
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Objective. The costimulatory interactions of the B7 family molecules CD80 and CD86 on antigen-presenting cells with their T-cell counter-receptors CD28 and CTLA-4 modulate T lymphocyte-mediated immune responses in a reciprocal manner. We investigated the possible aberrant production of soluble (s) forms of the T-cell costimulatory molecules CD80, CD86, CD28 and CTLA-4 in plasma of patients with systemic lupus erythematosus (SLE), an autoimmune disease arising from T-lymphocyte dysregulation.
Methods. Plasma concentration and ex vivo production of soluble costimulatory molecules of 79 SLE patients with or without active disease and 40 sex- and age-matched healthy subjects were measured by enzyme-linked immunosorbent assay.
Results. Plasma sCTLA-4, sCD28, sCD80 and sCD86 concentrations of all SLE patients were significantly higher than concentrations in control subjects (all P<0.01). These increases were observed even in patients with inactive disease [SLE Disease Activity Index (SLEDAI) <3]. Plasma sCTLA-4 concentration in all SLE patients correlated significantly with SLEDAI score (r = 0.228, P = 0.043). Upon mitogen treatment of peripheral blood mononuclear cells, the percentage increases in ex vivo production of sCD28 and sCD80 and the percentage decrease in sCTLA-4 release were all significantly smaller in SLE patients with active disease than in healthy subjects (P<0.01, P<0.05 and P<0.0001, respectively).
Conclusion. The aberrant production of soluble T-cell costimulatory molecules is important in the immunopathogenesis of SLE, which occurs by the dysregulation of T-lymphocyte costimulation. Plasma sCTLA concentration could potentially serve as a surrogate marker of SLE disease activity.
KEY WORDS: SLE, CTLA-4, CD28, CD80, CD86
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Introduction
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Systemic lupus erythematosus (SLE) is a prototypic systemic autoimmune disease characterized by various immunological abnormalities, including dysregulated activation of both T and B lymphocytes and subsequent polyclonal activation of circulating B lymphocytes that produce a large quantity of autoreactive antibodies [1, 2]. It has been shown that the activation of autoantibody-producing B cells is dependent on T-cell help through cytokines and costimulatory molecules. The initiation of T-cell activation requires a primary signal delivered by the antigenic peptide presented by major histocompatibility complex (MHC) molecules and a non-specific signal generated by the interaction of costimulatory molecules [3, 4]. The costimulatory signal results from the interaction of CD28 on T cells with the B7 family B7-1 (CD80) and B7-2 (CD86) on antigen-presenting cells (APCs) [5, 6]. Resting APCs are negative for CD80 and CD86 expression but monocytes and dendritic cells constitutively express CD86 [7]. Expression of CD80 is mainly activation-induced [7]. Cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4/CD152) is a member of the immunoglobulin superfamily and a structural homologue of CD28 [8, 9]. CTLA-4 is only expressed on activated T-helper (Th) cells and plays a negative regulatory role in the T-cell response [8, 9]. CD28 and CTLA-4 bind the same ligands, CD80 and CD86, expressed on APCs, but CTLA-4 has a 20- to 50-fold higher affinity than CD28 [10]. Therefore, CD28 provides a critical costimulatory signal essential for the initiation and progression of T-cell immunity [11], and CTLA-4 can actually down-regulate T-cell function [8].
Recent studies have provided evidence that peripheral mechanisms of T-cell tolerance are essential for controlling self-reactive T cells. The elimination of the peripheral mechanisms of T-cell tolerance results in the development of autoimmune disease [12, 13]. Genetic studies indicated that there is an association of CTLA-4 gene polymorphisms with susceptibility to SLE [14] and other autoimmune diseases [13]. A soluble form of CTLA-4 (sCTLA-4) was found to be expressed in non-stimulated human T cells and to be released into human plasma [15, 16]. Some previous studies showed elevation of plasma sCTLA-4 concentration in SLE [17] and autoimmune thyroid disease [18], but Hebbar et al. did not observe any significant changes [19]. In animal studies, CTLA-4 immunoglobulin was found to modify the development of lupus [20] and inhibit the onset of murine lupus nephritis [21], probably through the blockage of B7CD28 interaction. CTLA-4 knockout mice exhibit a profound spontaneous autoimmune disease [22]. Apart from these findings, recent studies have demonstrated that there is significant elevation of serum soluble CD28 (sCD28) concentration [19], cell surface expression of CD80 and CD86 on peripheral blood T lymphocytes [23], and CD86 on B lymphocytes [24] in SLE patients compared with healthy control subjects. Defective interferon (IFN)-
-induced up-regulation of CD80 and CD86 expression on SLE monocytes has been postulated to be a factor in the pathogenesis of SLE [25]. In fact, enhancement of CD86 expression on B cells by another costimulatory molecule CD40L (CD154) is essential for polyclonal antibody production [26].
In view of the above findings, it is evident that dysregulation of the T- and B-cell costimulatory pathways and CTLA-4/CD28:B7-1,2 interaction are related to the development of SLE. However, the plasma levels, the mechanisms for the production of sCTLA-4, sCD28, sCD80 and sCD86, and their correlation with SLE disease activity have not been well elucidated. In an attempt to further evaluate the immunopathological roles of T-cell costimulatory molecules and to search for potential surrogate markers in SLE, we investigated the plasma concentration and ex vivo production of sCD28, sCTLA-4, sCD80 and sCD86 from peripheral blood mononuclear cells (PBMC) in SLE patients and compared them with data from normal healthy subjects.
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Materials and methods
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SLE patients, control subjects and blood samples
Seventy-nine Chinese SLE patients were recruited at the rheumatology out-patient clinic of the Prince of Wales Hospital, Hong Kong. Diagnosis of SLE was established according to the 1982 revised American Rheumatism Association (ARA) criteria [27], and disease activity was evaluated using the SLE Disease Activity Index (SLEDAI) score [28]. The SLE patients were divided into two groups: the active disease group (ASLE, n = 52) and the inactive disease group (ISLE, n = 27). Active lupus was defined as a SLEDAI score >3. Forty sex- and age-matched healthy Chinese volunteers were recruited as control subjects (NC group). Twenty millilitres of venous peripheral blood was collected in EDTA (ethylenediamine tetraacetate) from each patient and control subject. The above protocol was approved by the Clinical Research Ethics Committee of The Chinese University of Hong KongNew Territories East Cluster Hospitals, and informed consent was obtained from all participants.
Whole blood assay
The method of Viallard et al. (1999) was adopted [29]. After a maximum storage period of 1 h of collected EDTA blood at room temperature, blood samples were diluted 1:1 with RPMI 1640 (Gibco Laboratories, NY, USA), and 1 ml aliquots were dispensed in each well of a 24-well plate (Nalge Nunc International, IL, USA). The blood culture was then incubated with or without the T-cell mitogen phytohaemagglutinin (PHA) (Sigma, MO, USA) at 5 µg/ml, and the B-cell and macrophage mitogen lipopolysaccharide (LPS) at 25 µg/ml (Sigma) for 24 h at 37°C in a 5% CO2 atmosphere for the optimal activation of macrophages, T cells and B cells. After incubation, the cell-free supernatant from ex vivo cultures was harvested and stored at 70°C for subsequent enzyme-linked immunosorbent assay (ELISA) of costimulatory molecules. The absolute number (cells/µl) of leucocytes (CD45+) of each whole blood sample was measured with the Multitest IMK Kit with Trucount Tubes (Becton Dickinson, CA, USA) using the lyse/no-wash method with a four-colour FACSCalibur flow cytometer (Becton Dickinson) [30]. To normalize the individual difference in leucocyte number of each whole blood sample, the ex vivo production of costimulatory molecules was expressed as ng/106 leucocytes. The percentage increase in ex vivo production of costimulatory molecules was calculated as (median of amount produced by PHA-LPS group median of amount produced by medium control group)/(median of amount produced by medium control group).
Assay of sCTLA-4, sCD28, sCD80 and sCD86
Plasma and culture supernatant concentrations of sCTLA-4, sCD28, sCD80 and sCD86 of all SLE patients and control subjects were measured by ELISA (Bender Medsystems Diagnostics, Vienna, Austria).
Statistical analysis
Since concentrations of sCTLA-4, sCD28, sCD80 and sCD86 and SLEDAI did not have a Gaussian distribution, the MannWhitney rank sum test was used to analyse the differences in sCTLA-4, sCD28, sCD80 and sCD86 concentrations between patients and controls, and Spearman's rank correlation test was used to assess the correlations of plasma sCTLA-4, sCD28, sCD80 and sCD86 concentrations with SLEDAI. Results are expressed as median (interquartile range). All analyses were performed using the Statistical Package for the Social Sciences (SPSS) statistical software for Windows, version 9.0 (SPSS, IL, USA). P<0.05 was considered as indicating a significant difference.
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Results
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SLE patients and control subjects
The age, sex, SLEDAI score, duration of diagnosis, and drug treatment of the study populations are summarized in Table 1. We studied 52 SLE patients with active disease (ASLE group; 51 females and one male, mean±S.D. age 39±9 yr, range 1955) and 27 SLE patients with inactive disease (ISLE group; 26 females and one male, age 36±9 yr, range 1953). The mean time since the diagnosis of SLE at the time when patients were recruited for this study was 12.8±5.8 yr (range 1.829.2) and 11.2±6.5 yr (0.329.2) for the ASLE and ISLE groups, respectively. The SLEDAI scores of ASLE and ISLE patients were 7.2±3.6 (range 418) and 1.7±1.0 (range 03), respectively. Patients were being treated with prednisolone (ASLE, 6.7±4.9 mg daily, 80.8%; ISLE, 5.6±5.3 mg, 59.3%), hydroxychloroquine (ASLE, 216.7±56.5 mg daily, 46.2%; ISLE, 213.3±35.2 mg daily, 55.6%), azathioprine (ASLE, 65.0±23.5 mg daily, 38.5%; ISLE, 85.0±37.9 mg daily, 18.5%), or any combination of two or three of the drugs. Forty sex- and age-matched normal control subjects (39 females and one male, aged 40±9 yr, range 1955) were also recruited for this study.
Plasma sCTLA-4, sCD28, sCD80 and sCD86 concentrations
As shown in Table 2, sCTLA-4, sCD28, sCD80 and sCD86 were ubiquitously present in plasma, with significantly higher concentrations in all SLE patients and patient subgroups with active or inactive diseases than in control subjects (all P<0.05).
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TABLE 2. Plasma sCTLA-4, sCD28, sCD80 and sCD86 concentrations of ASLE and ISLE patients and the normal control (NC) group
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Plasma concentration of soluble costimulatory molecules and SLE disease activity
Plasma sCTLA-4 concentration exhibited a positive, significant correlation with SLEDAI score in all SLE patients (r = 0.228, P = 0.043; Fig. 1). Contrary to the above observation, plasma concentrations of other costimulatory molecules did not correlate with disease activity. Such lack of additional correlation persisted even when we redefined ASLE and ISLE using SLEDAI scores of 4 and 5 (instead of 3) as the cut-off (all P>0.05; data not shown).

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FIG. 1. Correlation of plasma sCTLA-4 concentration with SLEDAI in all SLE patients (n = 79). Data were analysed with Spearman's rank correlation test.
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Intercorrelation of plasma concentration of costimulatory molecules
Figure 2 shows that there was a significant and positive correlation between plasma sCTLA-4 concentration with sCD28 in the ASLE group (r = 0.426, P = 0.002) and in all SLE (ISLE + ASLE) patients (r = 0.324, P = 0.004). Similar correlations were also observed between sCD28 with sCD86 in the ASLE group (r = 0.383, P = 0.005) and all SLE (ISLE + ASLE) patients (r = 0.317, P = 0.004). However, there was no positive and significant correlation between plasma concentrations of sCD28 and sCD80, sCD80 and sCD86 in SLE patients with either active or inactive disease (P>0.05).

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FIG. 2. Correlations of plasma concentrations of sCD28 with sCTLA-4 and sCD86 in ASLE (A, B) and all SLE patients (C, D). Data were analysed with Spearman's rank correlation test.
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Ex vivo production of sCTLA-4, sCD28, sCD80 and sCD86
As shown in Table 3, the combined treatment of PHA and LPS could significantly suppress the ex vivo release of sCTLA-4, and increase the release of sCD28, from PBMC in the control group (both P<0.0001). It could also significantly increase the ex vivo release of sCD28 in ISLE patients and sCD80 in the control group (both P<0.05).
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TABLE 3. Ex vivo production and release of sCTLA-4, sCD28, sCD80 and sCD86 from mitogen activated-PBMC of ISLE, ASLE and NC groups
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The percentage decrease in ex vivo production of sCTLA-4 after incubation with PHA and LPS was significantly less in ISLE and ASLE patients than in control subjects (both P<0.0001, Table 3). There was also a significant difference in the percentage increase of sCD28 and sCD80 between the control subjects and ASLE patients (sCD28, P<0.001; sCD80, P<0.05; Table 3). However, there was no significant difference in activated ex vivo production and the percentage increase in sCD86 in control subjects and ISLE and ASLE patients (all P>0.05, Table 3).
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Discussion
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Previous studies have reported altered cell surface expression of CD28, CTLA-4, CD80 and CD86 from patients with SLE, rheumatoid arthritis (RA) and renal disease [7, 31, 32, 33]. Such aberrant expression of costimulatory molecules may contribute to the loss of self-tolerance and disease development in SLE and RA [7, 31]. Although the cell surface expression of CTLA-4, CD28, CD80 and CD86 on T cells, B cells and APCs have been studied, the production of soluble forms of the above T-cell costimulatory molecules has not been investigated in patients with SLE.
In the present study, we demonstrated that plasma concentrations of sCTLA-4, sCD28, sCD80 and sCD86 in SLE patients were significantly higher than those of control subjects (Table 2). It is noteworthy that these increases were observed even in SLE patients with inactive disease (SLEDAI <3). The elevation of plasma sCTLA-4 in all SLE patients correlated positively and significantly with disease activity (Fig. 1). In addition, there was significant and positive correlation between plasma sCTLA-4 and sCD28, sCD28 and sCD86 in all SLE patients, in particular those with active disease (ASLE group; Fig. 2). As also observed by us, the plasma sCTLA-4, sCD28, sCD80 and sCD86 concentrations in SLE patients did not show any correlation with the doses of prednisolone, hydroxychloroquine and azathioprine.
sCTLA-4 mRNA has been reported to be constitutively expressed on non-stimulated T cells, and its expression is down-regulated after activation [16]. A previous study has suggested that sCTLA-4 plays a more important role than membrane (m)CTLA-4 in the early stage of the immune response because sCTLA-4 is constitutively expressed on non-stimulated T cells, while mCTLA-4 is only expressed on T cells upon activation [17]. Moreover, sCTLA-4 has been shown to have immunoregulatory properties in vitro [16]. Regarding the circulating sCTLA-4 concentration in SLE patients, inconsistent levels have been reported, probably resulting from discrepancies and heterogeneity among the SLE patients recruited in these two studies [17, 19]. By using different SLEDAI cut-off values, including 3, 4 and 5, to classify patients with active or inactive lupus, we attempted to evaluate the clinical significance of the plasma concentrations of sCTLA-4 and other costimulatory molecules in these SLE patients. It is interesting to note from our study that a coherent correlation of SLEDAI score with sCTLA-4 concentration existed throughout the entire SLE patient cohort, but not the subgroups, despite using different SLEDAI cut-off scores for the stratification of active disease. As discussed above, sCTLA-4 plays a more important role than membrane mCTLA-4 in the early stage of the immune response [17]. The above observation suggests that increased production and subsequent secretion of CTLA-4 into the plasma may start in the very early phase of the disease. Furthermore, a genetic study has also indicated that there is an association of CTLA-4 gene polymorphism with susceptibility to SLE [14]. It is apparent that the presence of sCTLA-4 may play important roles in the initiation and development of SLE disease, and plasma sCTLA-4 concentration could potentially serve as a surrogate marker of SLE disease activity.
Previously, patients with either active or inactive disease have been shown to exhibit a decreased mean percentage of CD28+ peripheral blood T cells due to the accelerated apoptosis of these cells [34]. However, we demonstrated a significant elevation of soluble form of CD28 in patients with inactive and active disease (Table 2), which concurs with the results reported from other study [19]. It has also been suggested that sCD28 could be produced either by shedding of the membrane form, or from alternative mRNA splicing [35], but recent results of PCR analysis have suggested that the elevation of sCD28 in the blood circulation is more likely to be due to the shedding of the membrane form [19].
sCTLA-4 may block the interaction between B7 (CD80, CD86) on APCs and mCTLA-4 on T cells, thereby interfering with the inhibitory signal sent to T cells to enhance the immune response [17]. On the other hand, sCTLA-4 may also bind B7 expressed on APCs and thus interfere with B7:CD28-mediated costimulation of T-cell responses [16]. Our observation of a positive and significant correlation between sCD28 and sCTLA-4 in all SLE patients, particularly those with active disease (Fig. 2), does suggest that sCD28 and sCTLA-4 play important roles in modulating the activation of T cells in SLE patients, thereby leading to the exacerbation of SLE disease activity. However, the detailed immunopathological activity of these soluble costimulatory molecules in the blood circulation of SLE patients requires further in-depth investigation.
Our ex vivo experiments also confirmed that sCTLA-4 expression was down-regulated while sCD28 was upregulated in PBMC after mitogen activation in control subjects and SLE patients with inactive disease. The above opposite effect is probably due to the reciprocal activity of CTLA-4 and CD28 for T-cell activation. It has been shown that sCTLA-4 mRNA expression is down-regulated after normal activation [16]. However, our results on activated PBMC from ASLE patients did not show any significant regulatory effect for the production of sCTLA-4 and sCD28 (Table 3). This further suggests that there may be dysregulation of CTLA- and CD28-mediated costimulatory mechanisms for T-cell activation in SLE, especially in more severely ill patients. In general, there was no marked significant change in the production of sCD80 and sCD86, except that the activated PBMCs showed a decreased percentage increase in the production of sCD80 in ASLE (Table 3). Whether the decreased ex vivo induction of sCD80 is related to disease development in the ASLE groups is not known. As mCD86 is highly expressed on CD8+ T cells while mCD80 is expressed mainly on CD4+ T cells [23], these two molecules may have different immunological roles and mechanisms for the generation of their soluble molecules. It may be the reason why sCD86 could not be induced ex vivo in any of the groups (normal control, ISLE and ASLE subjects).
The exact causes and mechanisms underlying the up-regulation of the production of the soluble costimulatory molecules in the plasma of SLE patients remains largely unknown, it is possible that the elevated production of soluble costimulatory molecules is influenced by the aberrant production of cytokines and chemokines. Indeed, we have shown significant elevation of concentrations of plasma proinflammatory cytokines (IL-18, IL-17, IL-12), Th2 cytokine (IL-4) [36], chemokine IL-8, regulated upon activation normal T-cell expressed and secreted (RANTES), monocyte chemoattractant protein (MCP)-1, IFN-
-inducible protein (IP)-10, and monokine induced by IFN-
(MIG) in SLE patients (data not shown). The elevation of IL-18 has been demonstrated to be significantly and positively correlated with SLEDAI [37], relating to the development of renal disease [38]. The B7-CD28/CTLA-4 costimulation can regulate T-cell chemotaxis and differentiation, probably through the activation of inflammatory cytokines and chemokines [39, 40]. Therefore, the dysregulation of T-cell functions by the elevation of soluble costimulatory molecules, such as sCD28 and sCD80, and proinflammatory cytokines and chemokines may lead to inflammation, particularly in SLE patients with more severe disease. However, it is not clear from the present studies whether aberrant expression of costimulatory molecules in SLE represents a primary defect that contributes to disease pathogenesis directly or instead represents a secondary event.
In summary, we have demonstrated elevated concentrations of plasma sCTLA-4, sCD28, sCD80 and sCD86 in SLE patients with active and inactive disease, as well as a positive and significant correlation between plasma sCTAL-4 concentration and disease activity. Taken together with findings on the aberrant ex vivo production of these costimulatory molecules, the above results should provide new postulates for their potential immunopathological roles in the exacerbation of SLE disease, and should facilitate the development of novel surrogate markers of disease activity, such as sCTLA-4. In view of recent advances in the exploration of therapeutic agents targeting T-cell activation in autoimmune disease [41], it might be possible to use therapeutic agents such as antibodies against the soluble form of the costimulatory molecules CTLA-4, CD28, CD80 and CD86 in the treatment of SLE.
The authors have declared no conflicts of interest.
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References
|
---|
- Mills JA. Systemic lupus erythematosus. N Engl J Med 1994;330:18719.[Free Full Text]
- Kotzin BL. Systemic lupus erythematosus. Cell 1996;85:3036.[CrossRef][ISI][Medline]
- Chambers CA, Allison JP. Co-stimulation in T cell responses. Curr Opin Immunol 1997;9:396404.[CrossRef][ISI][Medline]
- Greenfield EA, Nguyen KA, Kuchroo VK. CD28/B7 costimulation: a review. Crit Rev Immunol 1998;18:389418.[ISI][Medline]
- Linsley PS, Clark EA, Ledbetter JA. T-cell antigen CD28 mediates adhesion with B cells by interacting with activation antigen B7/BB-1. Proc Natl Acad Sci USA 1990;87:50315.[Abstract/Free Full Text]
- Azuma M, Ito D, Yagita H et al. B70 antigen is a second ligand for CTLA-4 and CD28. Nature 1993;366:769.[CrossRef][ISI][Medline]
- Sfikakis PP, Via CS. Expression of CD28, CTLA4, CD80, and CD86 molecules in patients with autoimmune rheumatic diseases: implications for immunotherapy. Clin Immunol Immunopathol 1997;83:1958.[CrossRef][ISI][Medline]
- Walunas TL, Bakker CY, Bluestone JA. CTLA-4 ligation blocks CD28-dependent T cell activation. J Exp Med 1996;183:254150.[Abstract/Free Full Text]
- Salomon B, Bluestone JA. Complexities of CD28/B7: CTLA-4 costimulatory pathways in autoimmunity and transplantation. Annu Rev Immunol 2001;19:22552.[CrossRef][ISI][Medline]
- Linsley PS, Brady W, Urnes M, Grosmaire LS, Damle NK, Ledbetter JA. CTLA-4 is a second receptor for the B cell activation antigen B7. J Exp Med 1991;174:5619.[Abstract/Free Full Text]
- Lenschow DJ, Walunas TL, Bluestone JA. CD28/B7 system of T cell costimulation. Annu Rev Immunol 1996;14:23358.[CrossRef][ISI][Medline]
- Bluestone JA. Is CTLA-4 a master switch for peripheral T cell tolerance? J Immunol 1997;158:198993.[Abstract]
- Kristiansen OP, Larsen ZM, Pociot F. CTLA-4 in autoimmune diseasesa general susceptibility gene to autoimmunity? Genes Immun 2000;1:17084.[CrossRef][ISI][Medline]
- Ueda H, Howson JM, Esposito L et al. Association of the T-cell regulatory gene CTLA4 with susceptibility to autoimmune disease. Nature 2003;423:50611.[CrossRef][ISI][Medline]
- Magistrelli G, Jeannin P, Herbault N et al. A soluble form of CTLA-4 generated by alternative splicing is expressed by nonstimulated human T cells. Eur J Immunol 1999;29:3596602.[CrossRef][ISI][Medline]
- Oaks MK, Hallett KM, Penwell RT, Stauber EC, Warren SJ, Tector AJ. A native soluble form of CTLA-4. Cell Immunol 2000;201:14453.[CrossRef][ISI][Medline]
- Liu MF, Wang CR, Chen PC, Fung LL. Increased expression of soluble cytotoxic T-lymphocyte-associated antigen-4 molecule in patients with systemic lupus erythematosus. Scand J Immunol 2003;57:56872.[CrossRef][ISI][Medline]
- Oaks MK, Hallett KM. Cutting edge: a soluble form of CTLA-4 in patients with autoimmune thyroid disease. J Immunol 2000;164:50158.[Abstract/Free Full Text]
- Hebbar M, Jeannin P, Magistrelli G et al. Detection of circulating soluble CD28 in patients with systemic lupus erythematosus, primary Sjogren's syndrome and systemic sclerosis. Clin Exp Immunol 2004;136:38892.[CrossRef][ISI][Medline]
- Finck BK, Linsley PS, Wofsy D. Treatment of murine lupus with CTLA4Ig. Science 1994;265:12257.[ISI][Medline]
- Mihara M, Tan I, Chuzhin Y et al. CTLA4Ig inhibits T cell-dependent B-cell maturation in murine systemic lupus erythematosus. J Clin Invest 2000;106:91101.[Abstract/Free Full Text]
- Waterhouse P, Penninger JM, Timms E et al. Lymphoproliferative disorders with early lethality in mice deficient in CTLA-4. Science 1995;270:9858.[Abstract]
- Abe K, Takasaki Y, Ushiyama C et al. Expression of CD80 and CD86 on peripheral blood T lymphocytes in patients with systemic lupus erythematosus. J Clin Immunol 1999;19:5866.[CrossRef][ISI][Medline]
- Bijl M, Horst G, Limburg PC, Kallenberg CG. Expression of costimulatory molecules on peripheral blood lymphocytes of patients with systemic lupus erythematosus. Ann Rheum Dis 2001;60:5236.[Abstract/Free Full Text]
- Liu MF, Li JS, Weng TH, Lei HY. Differential expression and modulation of costimulatory molecules CD80 and CD86 on monocytes from patients with systemic lupus erythematosus. Scand J Immunol 1999;49:827.[CrossRef][ISI][Medline]
- Nagafuchi H, Shimoyama Y, Kashiwakura J, Takeno M, Sakane T, Suzuki N. Preferential expression of B7.2 (CD86), but not B7.1 (CD80), on B cells induced by CD40/CD40L interaction is essential for anti-DNA autoantibody production in patients with systemic lupus erythematosus. Clin Exp Rheumatol 2003;21:717.[ISI][Medline]
- Tan EM, Cohen AS, Fries JF et al. The 1982 revised criteria for the classification of systemic lupus erythematosus. Arthritis Rheum. 1982;25:12717.[ISI][Medline]
- Bombardier C, Gladman DD, Urowitz MB, Caron D, Chang CH, the Committee on Prognosis studies in SLE. Derivation of the SLEDAI: a disease activity index for lupus patients. Arthritis Rheum 1992;35:63040.[ISI][Medline]
- Viallard JF, Pellegrin JL, Ranchin V et al. Th1 (IL-2, interferon-gamma (IFN-gamma)) and Th2 (IL-10, IL-4) cytokine production by peripheral blood mononuclear cells (PBMC) from patients with systemic lupus erythematosus (SLE). Clin Exp Immunol. 1999;115:18995.[CrossRef][ISI][Medline]
- Wong CK, Tse PS, Wong EL, Leung PC, Fung KP, Lam CW. Immunomodulatory effects of Yun Zhi and Danshen capsules in healthy subjectsa randomized, double-blind, placebo-controlled, crossover study. Int Immunopharmacol 2004;4:20111.[CrossRef][ISI][Medline]
- Liu MF, Kohsaka H, Sakurai H et al. The presence of costimulatory molecules CD86 and CD28 in rheumatoid arthritis synovium. Arthritis Rheum 1996;39:1104.[ISI][Medline]
- Warrington KJ, Takemura S, Goronzy JJ, Weyand CM. CD4+,CD28 T cells in rheumatoid arthritis patients combine features of the innate and adaptive immune systems. Arthritis Rheum 2001;44:1320.[CrossRef][ISI][Medline]
- Biancone L, Deambrosis I, Camussi G. Lymphocyte costimulatory receptors in renal disease and transplantation. J Nephrol 2002; 15:716.[CrossRef][ISI][Medline]
- Kaneko H, Saito K, Hashimoto H, Yagita H, Okumura K, Azuma M. Preferential elimination of CD28+ T cells in systemic lupus erythematosus (SLE) and the relation with activation-induced apoptosis. Clin Exp Immunol 1996;106:21829.[CrossRef][ISI][Medline]
- Magistrelli G, Jeannin P, Elson G et al. Identification of three alternatively spliced variants of human CD28 mRNA. Biochem Biophys Res Commun 1999;259:347.[CrossRef][ISI][Medline]
- Wong CK, Ho CY, Li EK and Lam CW. Elevation of proinflammatory cytokine (IL-18, IL-17, IL-12) and Th2 cytokine (IL-4) concentrations in patients with systemic lupus erythematosus. Lupus 2000;9:58993.[CrossRef][ISI][Medline]
- Wong CK, Li EK, Ho CY, Lam CW. Elevation of plasma interleukin-18 concentration is correlated with disease activity in systemic lupus erythematosus. Rheumatology 2000;39:107881.[Abstract/Free Full Text]
- Wong CK, Ho CY, Li EK, Tam LS, Lam CW. Elevated production of interleukin-18 is associated with renal disease in patients with systemic lupus erythematosus. Clin Exp Immunol 2002;130:34551.[CrossRef][ISI][Medline]
- Hidi R, Riches V, Al-Ali M et al. Role of B7-CD28/CTLA-4 costimulation and NF-kappa B in allergen-induced T cell chemotaxis by IL-16 and RANTES. J Immunol 2000;164:4128.[Abstract/Free Full Text]
- Burr JS, Kimzey SL, Randolph DR, Green JM. CD28 and CTLA4 coordinately regulate airway inflammatory cell recruitment and T-helper cell differentiation after inhaled allergen. Am J Respir Cell Mol Biol 2001;24:5638.[Abstract/Free Full Text]
- Racke MK, Stuart RW. Targeting T cell costimulation in autoimmune disease. Expert Opin Ther Targets 2002;6:27589.[CrossRef][Medline]
Submitted 8 November 2004;
revised version accepted 29 March 2005.