The Interleukin-1 Gene Cluster Polymorphisms Are Associated with Takayasu's Arteritis in Mexican Patients

Abstract

Takayasu's arteritis (TA) is a chronic inflammatory arteritis of unknown etiology involving mainly the aorta and its major branches. The interleukin (IL) 1β and IL-1 receptor antagonist have been playing an important role as regulators of inflammation. We investigated whether the polymorphisms at the IL-1B and IL-1RN gene cluster were associated with the genetic susceptibility to develop TA. We analyzed the IL-1B, IL-1F10.3, and IL-1RN polymorphisms in a sample of 58 TA patients, and 248 clinically healthy unrelated Mexican individuals by 5′ exonuclease TaqMan polymerase chain reaction. Polymorphic haplotypes were constructed after linkage disequilibrium analysis. We found increased frequencies of different polymorphisms (C allele and TC genotype of IL-1F10.3; TT genotype of IL-1RN.4; C allele and TC genotype of IL-1RN6.1; G allele of IL-1RN6.2 and haplotypes “1T” and “1C” of IL-RN VNTR and IL-1RN6.1) in the group of TA when compared to healthy controls. On the other hand, decreased frequency of IL-1-511 TC genotype was found in the TA group compared to controls. IL-1B and IL-1RN gene polymorphisms could be involved in the risk of developing TA in the Mexican population. These associations were independent of the affected vessels.

Introduction

T akayasu's arteritis (TA), also known as pulseless disease, is a chronic inflammatory arteritis affecting large vessels, predominantly the aorta and its main branches. Vessels inflammation leads to wall thickening, stenosis, fibrosis, and thrombus formation. Acute inflammation may destroy the arterial media and lead to aneurysm formation (Numano and others 2000). TA clinical manifestations usually appear in the second or third decade of life and it is most common in Japan, India, South East Asia, and Mexico; women being more frequently affected than men (Numano and others 2000; Johnston and others 2002).

Vascular inflammation of TA originates in the vasa vasorum and it is followed by infiltration of several inflammatory cells, leading to the formation of granulomas. At this stage, the production of inflammatory mediators is markedly increased (Noguchi and others 1998; Inder and others 2000). Previous studies have reported increased expression of interleukin (IL)-1 and IL-6, locally produced, in aortic tissues from patients suffering from TA (Seko and others 1996).

IL-1 may mediate the inflammatory response occurring in the vascular wall by activating monocytes and expression of adhesion molecules on endothelial cells, inducing secretion of other cytokines, chemokines, growth factors, and stimulating smooth muscle cells proliferation (Dinarello 1993; Dinarello 1996). In addition, IL-1 may enhance atherosclerosis by promoting vascular smooth muscle cells proliferation (Libby and others 1986b), increasing endothelial cell procoagulant activity (Libby and others 1986a), and by affecting lipid metabolism (Lopes-Virella 1993). Moreover, IL-1 is a potential proinflammatory agent that has a central role in tissue destruction (Hutyrova and others 2002). The most important members of the IL-1 family are the IL-1α, IL-1β, and IL-1 receptor antagonist (Ra). The common polymorphisms of the genes corresponding to the IL-1 family members are located within their regulatory regions. As a consequence, IL-1 gene polymorphisms have a potential modulating role in IL-1 proteins production, and are related with the development of several diseases (Moos and others 2000).

IL-1Ra is an IL-1 natural competitive inhibitor, acting by occupying cell surface receptors without triggering signal transduction (Ma and others 2002). IL-1Ra plays a role as an important regulator of inflammation and its corresponding gene (IL-1RN) contains several polymorphisms included RN.4T>C, RN6.1C>T, RN6.2C>G, and a variable number of tandem repeat (VNTR) of 86 bp sequence in intron 2 (Garcia-Gonzalez and others 2001).

Another gene included within the 360-kb region widely expressed is IL-1 F10.3, including on activated monocytes and B cells, and signal through a range of IL-1 receptors (Laurincova 2000; Smith and others 2000).

IL-1β is the predominant circulating isoform of IL-1 in human beings (Lopes-Virella 1993; Hutyrova and others 2002). Allelic polymorphism at position IL-1B −511 has been described to represent a C/T single nucleotide polymorphism (SNP).

As key mediators of inflammation, IL-1β, IL-1F10, and IL-1Ra are expected to play a major role in the pathogenesis of inflammatory vascular diseases, particularly in TA; an increase in the synthesis of IL-1β has been demonstrated in human arterial plaques in patients with cardiovascular disease (Tipping and others 1991; Galea and others 1996; Hasdai and others 1996). Furthermore, IL-1RN allele 2 genotype (IL-RN*2) has been found associated with single-vessel cardiovascular disease (SVCD) (Francis and others 1999). Considering that TA involves an intense inflammatory process and that cardiovascular disease is a common feature in TA patients, we have postulated that IL-1B, IL-1F10.3, and/or IL-1RN gene polymorphisms participate in the susceptibility to the development of this disease.

Material and Methods

Subjects

A total of 58 patients with TA clinically evaluated according to the American College of Rheumatology were included in this study. Clinical classification of TA was defined in 5 subgroups as proposed by Hata: (1) type I was presumed in patients with involvement of the aortic arch; (2) type IIa was confined to the ascending aorta and aortic arch, and type IIb confined to the ascending aorta, aortic arch, and descending aorta without involvement of the celiac artery; (3) type III was characterized by involvement of the descending aorta (from the end of aortic arch to the femoral artery); (4) type IV was presumed in patients with involvement of abdominal aorta and renal arteries; and (5) type V was presumed in patients with involvement of all the aorta and its branches. In each type, coronary and pulmonary arteries may be involved (Dabague and Reyes 1996; Hata and others 1996).

Blood pressure was measured after 5 min in a sitting position. The hypertension criteria were when the patients had above 90 mmHg for diastolic pressure and above 140 mmHg for systolic pressure in at least 3 recordings in different days.

The control group included 248 clinically healthy unrelated Mexican individuals recruited at the National Cardiology Institute “Ignacio Chávez” in Mexico City. Lack of known inflammatory-associated diseases, hypertension, familial histories of DM2, and coronary heart disease, as well as normal body mass index and plasma lipid levels, were the inclusion criteria for control subjects.

The study was conducted in accordance with the Declaration of Helsinki, and was approved by the Institutional Ethics Committee of the National Cardiology Institute, “Ignacio Chávez.” Informed written consent was obtained from all participants.

Genotyping

Genomic DNA was isolated from the blood samples using the salting out method (Miller and others 1988). The VNTR of IL-1RN intron 2 polymorphism (rs2234663) was analyzed as described, the PCR products were analyzed by electrophoresis on a 3% agarose gel stained with ethidium bromide. Allele 1 (4 repeats) was 410 base pairs (bp), allele 2 (2 repeats) 240 bp, allele 3 (3 repeats) 325 bp, allele 4 (5 repeats) 500 bp, and allele 5 (6 repeats) 595 bp (Tarlow and others 1993).

The IL1B-511C/T (rs16944), IL-1F10.3C/T (rs3811058), IL-1RN.4T/C (rs419598), IL-1RN6.1C/T (rs315952), and IL-1RN6.2C/G (rs315951) SNPs were genotyped using 5′ exonuclease TaqMan genotyping assays on a 7900HT Fast real-time PCR system, according to manufacturer's instructions (Applied Biosystems, Foster City, CA). Each SNP (allele and genotype) was manually and automatically defined with the allelic discrimination software (7300 System SDS Software^® by Applied Biosystems).

Statistical analysis

Allele and genotype frequencies of the studied polymorphisms in patients and healthy controls were obtained by direct counting. Hardy–Weinberg equilibrium (HWE) was calculated using the chi-square test. The significance of the differences between groups was determined using Mantel–Haenzel chi-squared analysis, which was combined with the 2×2 contingency tables using the EPISTAT statistical program (Version 5.0; USD Incorporated 1990, Stone Mountain, Georgia). Fisher's exact test was used if the number in any cell of the 2×2 contingence table was less than 5. The P values were corrected (pC) according to the number of specificities tested and the number of comparisons performed, and they were considered statistically significant if their value were <0.05. Relative risk with 95% confidence intervals (CI) was calculated as the odds ratio. Pairwise linkage disequilibrium (LD, D′) estimations between polymorphisms and haplotype reconstruction were performed with Haploview version 4:1 (Broad Institute of Massachusetts Institute of Technology and Harvard University, Cambridge, MA, USA). Multivariate analysis with analysis of variance and post hoc analysis (least significant difference) were performed for variances of hypertension and activity. Statistical significance was accepted at an alpha level of less than or equal to 0.05.

Results

General characteristics

A total of 58 TA patients, 2 men and 56 women, were studied. The mean age was at 28.0 years old with an interval of 13–52 years old. According to Hata classification (Hata and others 1996), the distribution of our patients was: type I=7 (12.1%), type II=7 (12.1%), type III=3 (5.2%), type IV=0 (0%), and type V=41 (70.7%). Thirty-eight subjects were in active phase (65.5%) and 20 in nonactive phase (34.5%). Hypertension was present in 27 (46.5%) TA patients (one with type I Hata's classification, 3 with type II and 23 with type V). The control group included 48 men and 200 women, with a mean age of 34.7 years old and an interval of 17–51 years old. Polymorphisms of IL-1B or IL1-RN were not associated with demographic or clinical parameters (data not shown).

IL-1B polymorphism

Allele and genotype frequencies of IL-1B genes in TA and healthy control groups are shown in Table 1. The observed and expected frequencies in both groups studied were in HWE.

Table 1.

Allele and Genotype Frequencies of the IL-1B and IL1F10.3 Polymorphisms in Takayasu's Arteritis Patients and Healthy Controls

	Takayasu's (n=58)		Controls (n=248)		pC	OR	95% CI
IL-1B-511
Allele	n	af	n	af
T	83	0.715	347	0.699
C	33	0.284	149	0.300
Genotype	n	gf	n	gf
TT	35	0.603	122	0.491
TC	13	0.224	103	0.415	0.020	0.41	0.20–0.83
CC	10	0.172	23	0.092
IL-1F10.3
Allele	n	af	n	af
T	72	0.620	395	0.796
C	44	0.379	101	0.203	10⁻⁴	2.39	1.51–3.77
Genotype	n	gf	n	gf
TT	15	0.258	158	0.637	6×10⁻⁷	0.20	0.10–0.39
TC	42	0.724	79	0.318	<10⁻³	5.62	2.86–11.15
CC	1	0.017	11	0.044

af, allele frequency; gf, genotype frequency; IL, interleukin; pC, P values were corrected; OR, odds ratio; CI, confidence interval.

The IL-1B genotype frequencies showed statistical differences in both polymorphisms studied. Decreased frequencies of the IL-1-511 TC, and IL-1 F10.3 TT genotypes were found in TA patients when compared to healthy controls (pC=0.020, OR=0.41 95% CI=0.20–0.83 and pC=6×10⁻⁷, OR=0.20 95% CI=0.10–0.39, respectively). On the other hand, increased frequencies of IL-1 F10.3 C allele and TC genotype were observed in TA patients when compared to healthy controls (pC=10⁻⁴, OR=2.39, 95% CI=1.51–3.77 and pC<10⁻³, OR=5.62, 95% CI=2.86–11.15, respectively).

IL-1RN polymorphism

We analyzed different polymorphism of IL-1 receptor antagonist. The allele and genotype frequencies are shown in Table 2. A significant increase frequency of RN.4 TT genotype was found in the group of TA when compared to the control group (pC=0.037, OR=2.10, 95% CI=1.12–3.97). With respect to IL1RN6.1 polymorphism, there were increased frequencies of the C allele and TC genotype (pC=0.008, OR=2.02, 95% CI=1.21–3.37 and pC=4×10⁻⁴, OR=3.18, 95% CI=1.65–6.15, respectively) in TA patients when compared to healthy controls. In the same polymorphism, the TT genotype showed a decreased frequency in TA patients (pC=0.001, OR=0.36, 95% CI=0.19–0.68). In regard to the IL1RN6.2 polymorphism, only the frequency of G allele was slightly increased in TA compared with healthy controls (pC=0.033, OR=1.77, 95% CI=1.08–2.90). Table 3 shows the analysis of variable number tandem repeats, were the frequency of 1 allele (4 repeats, size 410 bp) was increased in the TA patients with respect to the controls (pC=2.24×10⁻⁴, OR=2.74, 95% CI=1.58–4.82); as a consequence, the frequency of 1, 1 genotype was also increased in TA patients with respect to controls subjects (pC=3.4×10⁻³, OR=2.3, 95% CI=1.41–3.83). These associations were independent of the affected vessels on the basis of Hata's classification and the presence or not of the activity phase of the disease (data not shown).

Table 2.

Allele and Genotype Frequencies of the IL-1RN Polymorphisms in Takayasu's Arteritis Patients and Healthy Controls

	Takayasu's (n=58)		Controls (n=248)		pC	OR	95% CI
IL-1RN.4
Allele	n	af	n	af
T	90	0.775	335	0.675
C	26	0.224	161	0.324
Genotype	n	gf	n	gf
TT	37	0.638	113	0.455	0.037	2.10	1.12–3.97
TC	16	0.276	109	0.439
CC	5	0.086	26	0.104
IL-1RN6.1C>T
Allele	n	af	n	af
T	86	0.741	423	0.852
C	30	0.258	73	0.147	0.008	2.02	1.21–3.37
Genotype	n	gf	n	gf
TT	31	0.534	189	0.762	0.001	0.36	0.19–0.68
TC	24	0.414	45	0.181	4×10⁻⁴	3.18	1.65–6.15
CC	3	0.052	14	0.056
IL-1RN6.2C>G
Allele	n	af	n	af
G	89	0.767	323	0.651	0.033	1.77	1.08–2.90
C	27	0.232	173	0.348
Genotype	n	gf	n	gf
GG	33	0.569	108	0.435
GC	23	0.397	107	0.431
CC	2	0.034	33	0.133

Table 3.

Allele and Genotype Frequencies of the IL-1-VNTR Polymorphisms in Takayasu's Arteritis Patients and Healthy Controls

	Takayasu's (n=58)		Controls (n=248)		pC	OR	95% CI
Allele	n	af	n	af
1	94	0.810	312	0.629	2.24×10⁻⁴	2.74	1.58–4.82
2	19	0.163	173	0.348	2.24×10⁻⁴	0.43	0.27–0.68
Genotype	n	gf	n	gf
1, 1	39	0.672	104	0.419	3.4×10⁻³	2.3	1.41–3.83
1, 2	13	0.224	96	0.387
1, 3	1	0.017	6	0.024
1, 4	2	0.034	2	0.008
2, 2	3	0.052	38	0.153
4, 4	0	0.000	1	0.004

VNTR, variable number of tandem repeat.

Haplotypes analysis

The analysis of haplotypes showed one block in linkage disequilibrium with D′=0.85, composed by 2 polymorphisms (IL-RN VNTR and IL-1RN6.1 C>T). The analyses showed 3 different possible allele combinations (1T, 1C and 2T) with important differences between the studied groups (Table 4). Patients with TA showed increased frequencies of “1T” and “1C” haplotypes when compared to healthy controls (pC=0.04, OR=1.55, 95% CI=1.00–2.42 and pC=0.001, OR=2.20, 95% CI=1.29–3.74, respectively). On the other hand, the TA patients showed decreased frequency of the “2T” haplotype when compared to healthy controls (pC=0.002, OR=0.38, 95% CI=0.22–0.67).

Table 4.

Haplotype Frequencies of the IL-1RN VNTR, and IL-1 RN 6/1 T>C in Takayasu's Arteritis Patients and Healthy Controls

	Takayasu's (n=58)	Controls (n=248)	pC	OR	95% CI
Haplotype	Hf	Hf
1 T	0.576	0.505	0.04	1.55	1.00–2.42
2 T	0.169	0.353	0.002	0.38	0.22–0.67
1 C	0.251	0.174	0.001	2.20	1.29–3.74

Table shows only the haplotypes with significant associations. The order of the polymorphisms in the haplotypes is according to the positions in the chromosome (rs2234663 and rs315952).

Hf, haplotype frequencies.

Hypertension in Takayasu patients and controls

We compared the hypertensive subjects with TA versus control subjects according to IL-1B and IL-1RN genotypes. In this case, the IL1-F10.3 TT genotype showed a decreased frequency in hypertensive subjects with TA when compared to control subjects (31.3% vs. 66.5%, pC=0.002). Concerning IL-1RN polymorphisms, we found significant differences in IL1-RN VNTR for genotype 1,1 which have an increased frequency in TA group compared to healthy controls (71.9% vs. 49.1%, pC=0.030, OR=2.65, 95% CI=1.15–6.08).

Association with Hata's classification

The possible association of the IL-1B and IL-1RN polymorphisms with Hata's classification (Hata and others 1996), was analyzed in our group of patients. No association was detected in this analysis (data not shown).

Discussion

The inflammatory process in infectious and autoimmune diseases is regulated by a delicate balance between the proinflammatory and anti-inflammatory cytokines that have been reported in several studies (Dewberry and others 2000; Hutyrova and others 2002; Park and others 2006; Saruhan-Direskeneli and others 2006). Previous reports have found an association between gene variants and inflammatory lesions, such as coronary heart disease and others (Galea and others 1996; Dewberry and others 2000; Laurincova 2000; Moos and others 2000; Smith and others 2000; Garcia-Gonzalez and others 2001; Ma and others 2002). Nevertheless, in TA it is not well-known which of these components are present or how they can influence the progression of the lesions. In this study, we looked for a possible association between IL-1B and IL-1RN gene polymorphisms and TA development. To our knowledge, this study is the first one in TA to implicate IL-1B and IL-1RN gene variants in susceptibility and development of this disease.

Many studies have attempted to explore the association of different diseases with proinflammatory and chemotactic plasma cytokines (Libby and others 1986a, 1986b; Dinarello 1996; Francis and others 1999), including TA (Noris 2001; Saruhan-Direskeneli and others 2006). However, it should be emphasized that previous studies have focused on plasma cytokine levels that do not necessarily reflect cytokine concentrations of a tissue. Furthermore, cytokine plasma concentrations change along time as a result of several stimuli. Noris and others (1999) reported a correlation of IL-6 and RANTES (regulated upon activation, normal T cell expressed, and secreted) with TA during the active phase of the disease, suggesting that these cytokines contribute to the vasculitis lesions in this disease. In contrast, that study did not find any association of TA with IL-1β, which remained at low plasma levels during the active phase. Similar results were reported by Alcocer-Varela and others (1989); TA patients, in active or inactive phase, had normal production of IL-1.

In our study with 58 patients, 65.5% in active phase, it was found a statistical association between IL-1B and IL1-RN polymorphisms with TA risk. Taking together all these results, it could be stated that IL-1 has an important participation in the vasculitis lesions in TA, and, as a consequence, it should be considered as a parameter in the evaluation of this inflammatory disease.

Many studies have documented quantitative and qualitative alterations in cytokine productions over inflammatory reactions in infectious and autoimmune disease; some studies in rheumatoid arthritis patients showed that plasma concentration of IL-1 was elevated, and correlated with various parameters of the disease activity. Moreover, the production of endogenous IL-1Ra appeared to be insufficient to balance these higher IL-1 levels (Kay and Calabrese 2004); thus, facilitating the inflammatory process. In ankylosing spondylitis for example, another autoimmune disease, no significant differences was found in the polymorphic alleles of IL-1α and IL-1β genes. In contrast, the frequency of the IL-1RN VNTR*2 allele carriers was significantly increased in ankylosing spondylitis patients compared with local controls (McGarry and others 2001). Also, in the Alzheimer disease, the frequency of IL-1RN VNTR*2 allele was significantly lower in patients with dementia grade ≥6 (Bosco and others 2004). These results strongly suggest that the IL-1RN may be involved in the development of TA, independently of the IL-1B gene polymorphisms. However, our results clearly demonstrated that the IL-1B and IL-1RN gene polymorphisms strongly participate in the development and susceptibility to TA. We found important significant differences in all IL-1B polymorphisms studied (IL-1B −511 and F10.3) showing the participation of these alleles with response to the disease. What was interesting is that previous studies in our laboratory did not show an increase in plasma levels cytokines in the same group of patients studied (data not shown). This could indicate that the genetic component is present in the development of the disease without necessarily the presence of changes in plasmatic levels of these molecules. Despite existing controversial results in different populations (Iacoviello and others 2000; Zhang and others 2006; Arman and others 2008), our results seem to agree with the fact that the studied polymorphisms of the IL-1B gene participate in the susceptibility to TA. These results agree with others studies in inflammatory processes (Tipping and others 1991; Galea and others 1996; Moos and others 2000; Hutyrova and others 2002; Tolusso and others 2006; Zhang and others 2006); and they further support the participation of IL-1 genes in the development of the disease. Thus, we can conclude that C allele in both IL-1B and IL-1F10.3 genes is an important marker in TA.

IL-1Ra acts as an anti-inflammatory agent that inhibits the action of IL-1. Many studies have established the participation of the IL1RN polymorphism in many diseases, but the results are controversial. Arman and others (2008), showed that homozygote carrier for IL-1RN*2 allele may be a risk factor for SVCD. Similar results were reported by Francis and others (1999), but others reports indicated that IL1RN*2 allele was significantly associated with diseases as coronary artery disease (Marculescu and others 2002), atherosclerosis (Worrall and others 2003) or myocardial infarction (MI) (Manzoli and others 2000). In this study we found an association between allele IL1RN*1 yielding a 2.74-fold increase in the odds ratio for TA disease. In contrast with previous studies that have demonstrated an effect of IL1RN*2 allele on the gene expression (Bosco and others 2004; Arman and others 2008; van and others 2009), our results showed the IL1RN*1 allele and 1, 1 genotype is associated with TA disease, suggesting that the vasculitis process in this disease is enhanced by the IL-1RN gene polymorphisms.

It is known that polymorphic frequencies depend upon the ethnic population and, as a consequence, the immunological response could change. Our haplotype analysis showed an association between the 1T and 1C haplotypes and the risk of developing TA. These haplotypes includes the IL-1RN6/1 (rs315952) polymorphism associated with MI in a previous work (van and others 2009). However, in our haplotypes analysis, the polymorphism IL-1RN6/1 (rs315952) did not distinguish the haplotypes for risk (1T and 1C) and for protection (2T). The main difference is the presence of the 1 allele of the IL-1RN VNTR polymorphism for the risk haplotype and the presence of the 2 allele for the protective haplotype. The role of this susceptibility marker for TA is controversial, as has been observed in cardiovascular diseases. On the other hand, high and low levels of IL-1RN mRNA have been reported for the VNTR 2 allele; Tolusso reported that healthy blood donors homozygous for the VNTR 2 allele had decreased plasma levels of IL-1Ra as compared to nonallele 2 carriers (Tolusso and others 2006). In contrast, Hurme found that individuals with the VNTR 2 allele have 1.2-fold increased IL-1Ra plasma levels (Hurme and Santtila 1998). Besides, in vitro studies suggest a high production of IL-1Ra in individuals with the VNTR 2 allele (Danis and others 1995; Vamvakopoulos and others 2002). These findings are in agreement with ours; the protective haplotype included the VNTR 2 allele; thus, the individuals with this haplotype could produce more IL-1Ra, diminishing the proinflammatory effects of the IL-1 cytokine.

In other way, it should be emphasized that TA is an uncommon disease and, up-to-now, this study has included the largest number of patients for the analysis of the influence of interleukins in this disease. However, it is not enough to assert the influence of the IL-1RN and IL-1B polymorphisms in the development of TA, and the demonstration of such a possible influence should be further considered in meta-analysis studies.

TA patients with systolic arterial hypertension and high circulating levels of proinflammatory cytokines, like IL-1, TNF-α, and IL-6, have been reported. In spite of such evidence, we did not find any correlation between IL-1β or IL-1Ra, but we cannot eliminate the possibility of the participation of other genes in the development of TA and its clinical manifestations. Thus, several genes may modulate the response to inflammatory processes and future studies with other candidate genes with influence on hypertension, like the renin-angiotensin system, aldosterone, and other related cytokines, are needed. Also, the association of the IL-1B and IL-1RN gene polymorphisms with Hata's classification was analyzed. No association was observed, which would have been expected, especially in type V classification where the renal artery is involved. We considered that this no association with Hata's classification is due to the small number of patients with type V that we included in the study. In our study, only 41 patients with type V classification (23 with hypertension and 18 without hypertension) were included. Additional studies in a larger number of patients could help define the true role of these polymorphisms in the severity of the disease. On the other hand, we can show that IL1RN6.1 C and IL1RN6.2 G alleles although IL1RN.4 TT, IL1RN6.1 TC genotypes are genetic markers of risk in TA because of their increased frequency in this group.

The results suggest that IL-1B (IL1B-511, IL-1 F10.3) and IL-1RN (IL-1RN.4, IL-1RN 6.1, and VNTR) gene polymorphisms could be involved in the risk of developing TA in the Mexican population. This finding was independent of the affected vessels on the basis of Hata's classification and the presence or not of the activity phase of the disease. Additional studies in a large number of patients and in other populations could help to define the true role of these polymorphisms as risk factors for developing TA.

Footnotes

Acknowledgments

The authors are grateful to the study participants and we would like to thank María Elena González García for writing assistance. Institutional Review Board approval was obtained for all sample collections.

Author Disclosure Statement

No competing financial interests exist.

References

Alcocer-Varela

, Reyes-Lopez

, Sanchez-Torres

, Alarcon-Segovia

. 1989. Immunologic studies in patients with Takayasu's arteritis. III. Immunoregulatory changes. Clin Exp Rheumatol, 7,4:345–350.

Arman

, Soylu

, Yildirim

, Furman

, Ercelen

, Aydogan

, Coker

, Tezel

. 2008. Interleukin-1 receptor antagonist gene VNTR polymorphism is associated with coronary artery disease. Arq Bras Cardiol, 91,5:293–298.

Bosco

. others. 2004. Association of IL-1 RN*2 allele and methionine synthase 2756 AA genotype with dementia severity of sporadic Alzheimer's disease. J Neurol Neurosurg Psychiatry, 75,7:1036–1038.

Dabague

, Reyes

. 1996. Takayasu arteritis in Mexico: a 38-year clinical perspective through literature review. Int J Cardiol, 54,Suppl:S103–S109.

Danis

, Millington

, Hyland

, Grennan

. 1995. Cytokine production by normal human monocytes: inter-subject variation and relationship to an IL-1 receptor antagonist (IL-1Ra) gene polymorphism. Clin Exp Immunol, 99,2:303–310.

Dewberry

, Holden

, Crossman

, Francis

. 2000. Interleukin-1 receptor antagonist expression in human endothelial cells and atherosclerosis. Arterioscler Thromb Vasc Biol, 20,11:2394–2400.

Dinarello

. 1993. Modalities for reducing interleukin 1 activity in disease. Immunol Today, 14,6:260–264.

Dinarello

. 1996. Biologic basis for interleukin-1 in disease. Blood, 87,6:2095–2147.

Francis

. others. 1999. Interleukin-1 receptor antagonist gene polymorphism and coronary artery disease. Circulation, 99,7:861–866.

10.

Galea

, Armstrong

, Gadsdon

, Holden

, Francis

, Holt

. 1996. Interleukin-1 beta in coronary arteries of patients with ischemic heart disease. Arterioscler Thromb Vasc Biol, 16,8:1000–1006.

11.

Garcia-Gonzalez

, Lanas

, Santolaria

, Crusius

, Serrano

, Pena

. 2001. The polymorphic IL-1B and IL-1RN genes in the aetiopathogenesis of peptic ulcer. Clin Exp Immunol, 125,3:368–375.

12.

Hasdai

, Scheinowitz

, Leibovitz

, Sclarovsky

, Eldar

, Barak

. 1996. Increased serum concentrations of interleukin-1 beta in patients with coronary artery disease. Heart, 76,1:24–28.

13.

Hata

, Noda

, Moriwaki

, Numano

. 1996. Angiographic findings of Takayasu arteritis: new classification. Int J Cardiol, 54,Suppl:S155–S163.

14.

Hurme

, Santtila

. 1998. IL-1 receptor antagonist (IL-1Ra) plasma levels are co-ordinately regulated by both IL-1Ra and IL-1beta genes. Eur J Immunol, 28,8:2598–2602.

15.

Hutyrova

, Pantelidis

, Drabek

, Zurkova

, Kolek

, Lenhart

, Welsh

, Du Bois

, Petrek

. 2002. Interleukin-1 gene cluster polymorphisms in sarcoidosis and idiopathic pulmonary fibrosis. Am J Respir Crit Care Med, 165,2:148–151.

16.

Iacoviello

, Donati

, Gattone

. 2000. Possible different involvement of interleukin-1 receptor antagonist gene polymorphism in coronary single vessel disease and myocardial infarction. Circulation, 101,18:E193.

17.

Inder

, Bobryshev

, Cherian

, Wang

, Lord

, Masuda

, Yutani

. 2000. Immunophenotypic analysis of the aortic wall in Takayasu's arteritis: involvement of lymphocytes, dendritic cells and granulocytes in immuno-inflammatory reactions. Cardiovasc Surg, 8,2:141–148.

18.

Johnston

, Lock

, Gompels

. 2002. Takayasu arteritis: a review. J Clin Pathol, 55,7:481–486.

19.

Kay

, Calabrese

. 2004. The role of interleukin-1 in the pathogenesis of rheumatoid arthritis. Rheumatology (Oxford), 43,Suppl 3:iii2–iii9.

20.

Laurincova

. 2000. Interleukin-1 family: from genes to human disease. Acta Univ Palacki Olomuc Fac Med, 143:19–29.

21.

Libby

, Ordovas

, Auger

, Robbins

, Birinyi

, Dinarello

. 1986a. Endotoxin and tumor necrosis factor induce interleukin-1 gene expression in adult human vascular endothelial cells. Am J Pathol, 124,2:179–185.

22.

Libby

, Ordovas

, Birinyi

, Auger

, Dinarello

. 1986b. Inducible interleukin-1 gene expression in human vascular smooth muscle cells. J Clin Invest, 78,6:1432–1438.

23.

Lopes-Virella

. 1993. Interactions between bacterial lipopolysaccharides and serum lipoproteins and their possible role in coronary heart disease. Eur Heart J, 14,Suppl K:118–124.

24.

, Chen

, Pan

, Du

. 2002. Genomic polymorphism within interleukin-1 family cytokines influences the outcome of septic patients. Crit Care Med, 30,5:1046–1050.

25.

Manzoli

, Andreotti

, Leone

, Sperti

, Zecchi

, Di

. 2000. Vascular and haemostatic gene polymorphisms associated with non-fatal myocardial infarction: a critical review. Ital Heart J, 1,3:184–193.

26.

Marculescu

, Endler

, Schillinger

, Iordanova

, Exner

, Hayden

, Huber

, Wagner

, Mannhalter

. 2002. Interleukin-1 receptor antagonist genotype is associated with coronary atherosclerosis in patients with type 2 diabetes. Diabetes, 51,12:3582–3585.

27.

McGarry

, Neilly

, Anderson

, Sturrock

, Field

. 2001. A polymorphism within the interleukin 1 receptor antagonist (IL-1Ra) gene is associated with ankylosing spondylitis. Rheumatology (Oxford), 40,12:1359–1364.

28.

Miller

, Dykes

, Polesky

. 1988. A simple salting out procedure for extracting DNA from human nucleated cells. Nucleic Acids Res, 16,3:1215.

29.

Moos

, Rudwaleit

, Herzog

, Hohlig

, Sieper

, Muller

. 2000. Association of genotypes affecting the expression of interleukin-1beta or interleukin-1 receptor antagonist with osteoarthritis. Arthritis Rheum, 43,11:2417–2422.

30.

Noguchi

, Numano

, Gravanis

, Wilcox

. 1998. Increased levels of soluble forms of adhesion molecules in Takayasu arteritis. Int J Cardiol, 66,Suppl 1:S23–S33.

31.

Noris

. 2001. Pathogenesis of Takayasu's arteritis. J Nephrol, 14,6:506–513.

32.

Noris

, Daina

, Gamba

, Bonazzola

, Remuzzi

. 1999. Interleukin-6 and RANTES in Takayasu arteritis: a guide for therapeutic decisions? Circulation, 100,1:55–60.

33.

Numano

, Okawara

, Inomata

, Kobayashi

. 2000. Takayasu's arteritis. Lancet, 356,9234:1023–1025.

34.

Park

, Lee

, Park

, Lee

. 2006. Serum cytokine profiles and their correlations with disease activity in Takayasu's arteritis. Rheumatology (Oxford), 45,5:545–548.

35.

Saruhan-Direskeneli

. others. 2006. Interleukin (IL)-12, IL-2, and IL-6 gene polymorphisms in Takayasu's arteritis from Turkey. Hum Immunol, 67,9:735–740.

36.

Seko

, Sato

, Takagi

, Tada

, Matsuo

, Yagita

, Okumura

, Yazaki

. 1996. Restricted usage of T-cell receptor Valpha-Vbeta genes in infiltrating cells in aortic tissue of patients with Takayasu's arteritis. Circulation, 93,10:1788–1790.

37.

Smith

, Renshaw

, Ketchem

, Kubin

, Garka

, Sims

. 2000. Four new members expand the interleukin-1 superfamily. J Biol Chem, 275,2:1169–1175.

38.

Tarlow

, Blakemore

, Lennard

, Solari

, Hughes

, Steinkasserer

, Duff

. 1993. Polymorphism in human IL-1 receptor antagonist gene intron 2 is caused by variable numbers of an 86-bp tandem repeat. Hum Genet, 91,4:403–404.

39.

Tipping

, Lowe

, Holdsworth

. 1991. Glomerular interleukin 1 production is dependent on macrophage infiltration in anti-GBM glomerulonephritis. Kidney Int, 39,1:103–110.

40.

Tolusso

, Pietrapertosa

, Morelli

, De

, Gremese

, Farina

, Carniello

, Del

, Ferraccioli

. 2006. IL-1B and IL-1RN gene polymorphisms in rheumatoid arthritis: relationship with protein plasma levels and response to therapy. Pharmacogenomics, 7,5:683–695.

41.

Vamvakopoulos

, Green

, Metcalfe

. 2002. Genetic control of IL-1beta bioactivity through differential regulation of the IL-1 receptor antagonist. Eur J Immunol, 32,10:2988–2996.

42.

van

, Wettinger

, de Visser

, Vos

, Reitsma

, Rosendaal

, Bertina

, Doggen

. 2009. Haplotypes of the interleukin-1 receptor antagonist gene, interleukin-1 receptor antagonist mRNA levels and the risk of myocardial infarction. Atherosclerosis, 203,1:201–205.

43.

Worrall

, Azhar

, Nyquist

, Ackerman

, Hamm

, DeGraba

. 2003. Interleukin-1 receptor antagonist gene polymorphisms in carotid atherosclerosis. Stroke, 34,3:790–793.

44.

Zhang

, Zhong

, He

, Li

, Nie

, Wang

, Chen

. 2006. [The correlation between polymorphism at position −511C/T in the promoter region of interleukin 1B and the severity of coronary heart disease] Zhonghua Yi Xue Yi Chuan Xue Za Zhi, 23,1:86–88.