allele associated to behçet's disease and to anterior uveitis in Moroccan patients

doi:10.1684/abc.2011.0591

To cite this article: Radouane A, Oudghiri M, Chakib A, Naya A, Belhouari A, El Malki A, Bennani S. HLA-B*27 allele associated to Behc¸et’s disease and to anterior

HLA-B*27 allele associated to Behc¸et’s disease and to anterior uveitis in Moroccan patients

HLA-B*27 allèle associé à la maladie de Behc¸et et à une uvéite antérieure chez les patients marocains

Asmaa Radouane ¹ Mounia Oudghiri ¹ Abdelfettah Chakib ² Abdallah Naya ¹

Abderrahman Belhouari ³ Abdelouhab El Malki ⁴ Siham Bennani ⁴

1

Laboratoire de physiologie et génétique moléculaire, Faculté des Sciences, Université Hassan II Aïn Chock, Maârif, Casablanca, Maroc

<oudghiri.m@menara.ma>

<mouniaoudghiri@gmail.com>

<m.oudghiri@fsac.ac.ma>

2

Hôpital Ibn Rochd, Casablanca, Maroc

3

Faculté des Sciences, Ben M’Sik, Casablanca, Maroc

4

Institut Pasteur, Casablanca, Maroc

Article received 7 January 2011, accepted 18 February 2011

Abstract. Human leukocyte antigen HLA-B51 is the most strongly associated gene with Behc¸et disease (BD) in different ethnic populations. We analyze the influence of HLA-B alleles in BD predisposition in Moroccan population and its association with clinical manifestations. The HLA-B phenotype frequencies were analyzed by serologic HLA class I typing and by polymerase chain reaction sequence-specific oligonucleotide (PCR-SSO) reverse dot blot hybridization in 120 unrelated Moroccan patients: all of whom fulfilled the international study group criteria for Behc¸et’s disease, and in 112 ethnically matched healthy controls. Besides HLA-B*51 allele (20%), a significant increased frequency of the HLA-B*27 allele was found in Moroccans patients with Behc¸et’s disease when compared to controls (13.3% of patients versus 2.7% of controls, chi square = 8.75, OR = 5.59, 95% IC [1.58-19.75] and particularly in the patients who presented an anterior uveitis (25% vs. 5.5%, p < 0.005).

Key words: association HLA, Beh¸cet’s Disease, HLA-B 27, Moroccan popula- tion, anterior uveitis

Résumé. L’implication du système HLA en particulier l’allèle HLA-B51 dans le développement de la maladie de Behc¸et (MB) a été rapportée par différentes études et dans diverses ethnies. Pour analyser l’influence du système HLA de classe I dans le développement de la MB dans la population marocaine et son association avec les manifestations cliniques, les fréquences alléliques ont été analysées dans un groupe de 120 patients marocains par biologie moléculaire (PCR-SSO). Tous les cas ont été colligés au Centre hospitalier universitaire Ibn Rochd, sélectionnés suivant les critères internationaux de la MB et comparés à un groupe de 112 individus contrôle de donneurs sains de même ethnie.

L’analyse statistique des résultats obtenus a montré, à côté de l’expression signi- ficativement élevée du HLA-B51 (20 %), celle également de l’allèle HLA-B27 (13,33 % des patients versus 2,67 % des contrôles, chi square = 8,75, OR = 5,59, 95% IC [1,58-19,75] et particulièrement chez les patients qui présentaient une uvéite antérieure (25 % vs 5,5 %, p < 0,005).

Mots clés : association HLA-B27, maladie de Beh¸cet, patients marocains, uvéite antérieure

Behc¸et’s disease (BD) is an inflammatory disorder of unknown cause, characterized by recurrent oral aphthous ulcers, genital ulcers, uveitis, and skin lesions [1]. A close association of the human leukocyte antigen HLA-B51 allele

with the disease suggests that genetic predisposition contri- butes to susceptibility to BD [2]. In addition, infections with agents such as herpes simplex virus [3, 4] and Streptococcus sanguis [5] have been implicated in the development of BD, although no specific infectious agent has been identified as its cause [6, 7].

Reprints: M. Oudghiri

HLA-B51 association with BD has been described in seve- ral ethnic groups [8-18]. However, the relative risk of HLA-B51 positive individuals to develop the disease fol- low the distribution of B51 allele around the world, although there are some communities, i.e. Inuit or North American Indian, who have high levels of HLA-B*51 and no reported disease. In most cases, the highest levels of HLA-B*51 fol- low the trade routes as does BD [19]. Furthermore, among the several B51 alleles (B*5101–5109), the B*5101 is the most frequently observed [20-24]. In a systematic review and meta-analysis of case-control genetic association stu- dies; they showed the strength of the association between BD and HLA-B51/B5 and its consistency across popula- tions of various ethnicities, this lends further support to this allele being a primary and causal risk determinant for BD [25].

In Moroccan patients, only two studies reported the dis- tribution of HLA alleles. In one of them, both alleles HLA-B*15 and HLA-B*51 have been found associated with BD with a frequency more important in women than in men [26]. Results were compared to a control group from the big Casablanca city. In the other study [27], HLA-B*51, HLA-B 58 and HLA-B 72 were been found the alleles asso- ciated with BD. The HLA-B*15 was not detected in this study where the control group was originated from a general Moroccan population without ethnic origin distinction.

The Moroccan population comprises different ethnic groups (Arabic speaking from west Morocco; Berber spea- king from the north of Morocco or Berber speaking from the south, Jewish communities . . . and so). It is characteri- zed by a great ethnic diversity. Several reports have shown that HLA gene frequencies correlate with geographically related population [28-34]. Each population exhibits some specific variants and some uncommon alleles. The choice of the control group is very important because of a great ethnic diversity of the Moroccan population.

In other populations the HLA B*27 [35] and HLA B*52 were the alleles that been found to be significantly increased in BD.

In the present study, we have analyzed the HLA-B poly- morphism in a group of 120 Moroccan BD patients, by comparison with 112 healthy controls [34] with the same ethnic origin, from the big Casablanca city. The association with the clinical manifestations and HLA-B expression was also investigated.

Patients and methods

Patients

The study included one hundred twenty Moroccan patients, coming from the Ibn Rochd’s Hospital and Pasteur

institute of Casablanca, all of whom fulfilled the internatio- nal study group criteria for Behc¸et’s disease (ISG+) with oral ulcers and two other criteria (recurrent genital ulcera- tion, eye lesions, skin lesions and positive pathergy test).

There were 84 males (70%) and 36 females (30%). Age ranged from 14 to 53 years (mean: 31 years, sex ratio: 2.3).

The control group of one hundred and twelve unrelated healthy Moroccan that was included in this study was a group of blood donors who volunteered for this study all of them were originated from the big Casablanca city and were of the same ethnic origin like the patients group.

All subjects were informed about the objectives and methods of the study and gave their consent.

HLA typing

Peripheral blood lymphocytes were isolated by using Ficoll density gradient separation. Genomic DNA was isola- ted from peripheral EDTA anti-coagulated whole blood using the Wizard Genomic DNA Purification Kit (Qiagen, QIAamp ^® DNA Midi and Blood Midi Handbook). Generic HLA-B typing was performed by polymerase chain reac- tion sequence-specific oligonucleotide (PCR-SSO) reverse dot blot hybridization using the Dynal RELI SSO HLA-B test kits (INNO LiPA HLAB Update plus).

Statistical analysis

Allelic frequencies were determined by direct counting of the individuals carrying the allele considered. Odds ratios (OR) were calculated according to the Woolf’s formula, and were given with 95% confidence interval [CI of 95%]. The distribution of the alleles was compared between patients and controls using Chi-square ( ␹ ² ) test. And the p values were calculated using Fisher’s exact test. p value was consi- dered significant if it was < 0.05.

Results

Clinical characteristics of the 120 Moroccan BD patients included in this study are summarized in table 1. All patients presented oral ulcers. The other clinical symptoms were genital ulcers (80%), skin lesions (70%), Pathergy test in 60%, arthritis in 55%, uveitis in 42.5% (anterior in 40%

and posterior in 2.5%), neurological involvement in 5%, cardiovascular and gastrointestinal in 2,5% of the patients.

The frequency of posterior uveitis in these patients was low.

No data are available on other Moroccan studies of BD to compare.

HLA-B allele frequencies in patients and controls are shown in table 2. There was no difference in the frequency of HLA-B*15 allele between patients and controls; 6.66%

vs. 6.25%, (OR = 1.07, 95% CI [0.37-3.05], p = 0.89).

Table 1. Patients’ clinical characteristics.

Manifestation Frequency (%)

Males Females

Oral ulcers 100 84 36

Genital ulcers 80 66 30

Skin lesion 70 58 26

Pathergy test 60 48 24

Arthritis 55 48 18

Anterior uveitis 40 35 13

Posterior uveitis 2.5 2 1

Neurological involvement 5 2 3

Cardiovascular disease 2.5 2 1

Gastrointestinal lesions 2.5 1 2

The frequency of HLA-B*27 was significantly higher in BD patients compared to controls; 13.33% vs. 2.67%, (OR = 5.59, 95% CI [1.58-19.75], p = 0.003). Only one patient, but none of controls were B*27 homozygote. The HLA- B*51 frequency was significantly higher in patients group 20% vs. 8.92%, in controls (OR = 2.55, 95% CI [1.16-5.61], p = 0.017). All patients and controls were B*51 heterozy- gote. The distribution of HLA-B allele according to sex in patients (table 3) showed a significant increase in frequen- cies of HLA-B*27 and B*51 alleles (15.47% vs. 2.56% and 22.61% vs. 7.69% respectively) for men. Finally, HLA-B associations were analyzed according to the some clinical manifestations of the disease. The results are summarized in table 4.

Table 2. HLA-B allele frequencies in Moroccan patients with Behc¸et’s disease (BD).

Alleles Patients with BD n = 120

(%)

Healthy controls n = 112

(%)

Chi square

P Value OR 95%

Confidence Interval

B*05 1 (0.83) 3 (2.67) 1.16 0.28 0.31 0.003-3.02

B*07 3 (2.5) 6 (5.35) 1.27 0.26 0.64 0.11-1.84

B*08 6 (5) 0 (0.0) 5.75 0.01 - -

B*13 1 (0.83) 1 (0.89) 0.002 0.96 0.93 0.06-15.05

B*14 4 (3.33) 5 (4.46) 0.2 0.65 0.74 0.19-2.83

B*15 8 (6.66) 7 (6.25) 0.02 0.89 1.07 0.37-3.05

B*16 1 (0.83) 3 (2.67) 1.16 0.28 0.31 0.03-3.02

B*17 1 (0.83) 3 (2.67) 1.16 0.28 0.31 0.03-3.02

B*18 1 (0.83) 5 (4.46) 3.03 0.08 0.18 0.02-1.57

B*21 3 (2.5) 4 (3.57) 0.23 0.63 0.69 0.15-3.15

B*22 0 (0) 1 (0.89) 1.08 0.29 0 -

B*27 16 (13.33) 3 (2.67) 8.75 0.003 5.59 1.58-19.75

B*35 3 (2.5) 7 (6.25) 1.98 0.15 0.38 0.1-1.51

B*37 0 (0) 2 (1.87) 2.16 0.14 0 -

B*38 1 (0.83) 4 (3.57) 2.06 0.15 0.23 0.03-2.09

B*39 3 (2.5) 1 (0.89) 0.88 0.34 2.85 0.29-27.81

B*40 0 (0) 1 (0.89) 1.08 0.29 0 -

B*41 4 (3.33) 3 (2.67) 0.08 0.77 1.25 0.27-5.71

B*42 3 (2.5) 1 (0.89) 0.88 0.34 2.85 0.29-27.81

B*44 9 (7.5) 10 (8.92) 0.16 0.69 0.83 0.32-2.12

B*45 1 (0.83) 4 (3.57) 2.06 0.15 0.23 0.03-2.09

B*49 4 (3.33) 5 (4.46) 0.2 0.65 0.74 0.19-2.83

B*50 9 (7.5) 4 (3.57) 1.69 0.19 2.19 0.65-7.32

B*51 24 (20) 10 (8.92) 5.68 0.017 2.55 1.16-5.61

B*52 3 (2.5) 3 (2.67) 0.01 0.93 0.93 0.18-4.71

B*53 1 (0.83) 3 (2.67) 1.16 0.28 0.31 0.03-3.02

B*57 1/0.83) 2 (1.87) 0.41 0.52 0.46 0.04-5.14

B*58 3 (2.5) 2 (1.87) 0.14 0.70 1.41 0.23-8.6

B*59 1 (0.83) 0 (0.00) 0.94 0.33 - -

B*72 0 (0) 1 (0.89) 1.08 0.29 0 -

B*78 1 (0.83) 1 (0.89) 0.002 0.96 0.93 0.06-15.05

- 4 (3.33) 7 (6.25) 1.09 0.29 0.52 0.15-1.83

Table 3. Frequency of HLA B alleles in patients and controls according to sex.

HLA Males Females

Alleles Frequencies (%) Frequencies (%)

Patients with BD Controls P OR Patients with BD Controls P OR

n = 84 n = 78 (CI 95%) n = 36 n = 34 (CI 95%)

B*27 15.47 2.56 0.0046 6.96 8.33 2.94 0.331 3

1.52-31.93 0.3-30.35

B*51 22.61 7.69 0.008 3.51 13.88 11.76 0.79 1.3

1.32-9.33 0.3-4.94

BD: Behc¸et’s disease; OR: odd ratio; CI: confidence interval; n: number of patient or control; p: considered significant if it was < 0.05.

The frequency of the patients expressing the HLA-B*27 allele with the anterior uveitis manifestation was signifi- cantly higher compared to the patients of the same group without this manifestation (25% vs. 5.55% p = 0.002).

But we did not find any association between the HLA B*27 allele and skin lesions or arthritis. The HLA B*51 allele was not associated with the various manifestation studied.

Discussion

The genetic association between BD and the expression of HLA-B51 allele was described for the first time in 1982 by Ohno [2] in the Japanese population. The antigen HLA B*51 was present in 57% of patients versus 16% in the general population (p < 0.001). The association has been since confirmed in many other people of different ethnic and geographic groups (English, French, Italian, Greek, Turkish, Tunisian, Israeli, Iranian, Saudi, Kuwaiti, Chinese, Korean, Taiwanese and Mexican). The frequency of HLA B*51 varies from 13 to 79% in patients, and is two to three times higher than that observed in controls, regardless of the prevalence of this allele in the general population. The relative risk (defined by the odds ratios) of BD related to the presence of the B*51 allele varies from 3 to 15 [24] and OR ranges varies by geographic locations [25].

Our data showed that HLA B*51 allele expressed in 25%

of Moroccan BD patients and confers a relatively low risk (OR = 2.55) compared to that observed in most ethnic groups studied. Whereas, in eastern Mediterranean popula- tions and the external-East, the odd ratio is usually greater than 10. It is 11.7 in Saudi Arabian [17], 10.9 in Palestinian and Jordanian [11], 11.5 in Greeks [23], 18.2 in Israelis [12], and 16 in Italian [18]. Interestingly, the predisposing effect of HLA B*51 in Moroccans calculated for our study group was OR = 2.55. This confirms what has been found in Moroccan studies [26, 27] and in patients who are known

to be genetically related to the Moroccan population: Por- tuguese patients (OR = 2.38) [35], Tunisian patients with (OR = 2.77) [36] and in Spanish patients with (OR = 2.7) [14]

More surprising is our observation of a predisposition effect of HLA-B*27 to BD. This allele has never been incri- minated in susceptibility to BD in Moroccan population so far [26, 27]. We found 13.33% of patients expressing HLA-B*27 vs. 2.67% of control group. The association of HLA-B27 and BD was described for Portuguese patients [35]. A Turkish study showed the existence of a weak asso- ciation of BD and HLA-B*2702 allele [37]. In the other hand; 75% (12/16) of patients expressed HLA-B*27+ have anterior uveitis manifestations. The uveitis and systemic disease have been reported to be associated with the HLA- B*27 expression [38].

In this study we found that the HLA-BD expression may be associated with gender differences. As previously reported [16, 26, 30, 38], our results confirm that the prevalence of HLA B*27 and B*51 alleles were more frequent in males.

It was also reported that the HLAB27–associated syste- mic disease developed earlier in males than in females (31 vs. 37 years) [38]. Consequently, at onset of acute anterior uveitis, HLA-B27–associated systemic disease was more frequent in males than in females. However over time, it was observed that males and females were at equal risk of developing a HLA-B27–associated systemic disease [38]

after the onset of acute anterior uveitis.

These HLA-disease associations were also described in

other diseases, such as polyarthritis rheumatoid, multiple

sclerosis psoriasis and leukemia [39-41]. HLA-B*52 who

is a second sub-division of HLA B*5 is not associated with

the disease. HLA B*5101 and HLA B*52 differ only in

two amino-acids (position 63 and 67), localized in the site of

peptide binding at the level of a pocket which welcomes the

major anchored residue of the peptide (residue P2). These

positions are strongly involved in the specificity and the

affinity of the binding, and could have an important role in

the presentation of a pathogenic antigen [42].

Ta b le 4 . F requency of the clinical in v olv ement in patients e xpressed the HLA-B alleles associated with BD . Alleles Skin lesions (%) P OR Anterior uveitis (%) p OR Ar thritis (%) p OR IC IC IC HLA-B + - 95% + - 95% + - 95% N=8 4 N=3 6 N=4 8 N=7 2 N=6 6 N=5 4 B*27 N = 1 6 1.33 5.67 1.06 14.28 11.11 0.639 [0.4-4.44] 25 5.55 0.002 [1.71-18.85] 13.63 12.96 0.914 [0.37-3.06] B*51 24 = N 0.82 0.7 0.96 19.04 22.22 0.69 [0.32-2.13] 16.66 22.22 0.45 [0.27-1.79] 19.69 20.37 0.92 [0.39-2.36] n = n umber of patients; + : with the clinical manif estation; - : without clinical manif estation; P: corrected v alue w a s considered significant if it w a s < 0.05.

Conclusion

This work confirms the association of B*51 allele with BD in Moroccan population. A new HLA-B allele seems to play an important role in the BD, the HLA-B*27 allele with a special association with uveitis.

Acknowledgements. We thank the Ibn Rochd’s Hospital of Casablanca for their collaboration. We thank Dr. Maria Kabbaj for their critical review of this article. This work was supported by Pasteur Institute of Casablanca, Morocco.

Conflicts of interest: none.

References

1. Amoura Z, Guillaume M, Caillat-Zucman S, Wechsler B, Piette JC.

Physiopathologie de la maladie de Behc¸et. Rev Med Int 2006 ; 27 : 843-53.

2. Ohno S, Ohguchi M, Hirose S, Matsuda H, Wakisaka A, Aizawa M.

Close association of HLA-Bw51 with Behc¸et’s disease. Arch Ophthalmol 1982 ; 100 : 1455-8.

3. Sezer FN. The isolation of a virus as the cause of Behc¸et’s diseases.

Am J Ophthalmol 1953 ; 36 : 301-15.

4. Lee S, Bang D, Cho YH, Lee ES, Sohn S. Polymerase chain reac- tion reveals herpes simplex virus DNA in saliva of patients with Behc¸et’s disease. Arch Dermatol Res 1996 ; 288 : 179-83.

5. Anonymous. Skin hypersensitivity to streptococcal antigens and the induction of systemic symptoms by the antigens in Behc¸et’s disease : a multicenter study. The Behcet’s Disease. Research Committee of Japan.

J Rheumatol 1989 ; 16 : 506-11.

6. Direskeneli H. Behc¸et’s disease : Infectious etiology, new auto antigens, and HLA-B51. Ann Rheum Dis 2001 ; 60 : 996-1002.

7. Behcet H. Uber rezidivierende, aphthose, durchein Virus verursachte Geshwure am Munde, et al. Dematologische Wochenschrift 1937 ; 36 : 1152-7.

8. Al-Dalaan AN, al Balaa SR, el Ramahi K. Behc¸et’s disease in Saudi Arabia. J Rheum 1994 ; 21 : 658-64.

9. Al-Rawi ZS, Sharquie KE, Khalifa SJ, Al-Hadithi FM, Munir JJ.

Behc¸et’s disease in Iraqi patients. Ann Rheum Dis 1986 ; 45 : 987-97.

10. Alpsoy E, Yilmaz E, Coskun M, Savas A, Yegin O. HLA antigens and linkage disequilibrium patterns in Turkish Behc¸et’s patients. J Dermatol 1998 ; 25 : 158-62.

11. Arber N, Klein T, Meiner Z, Pras E, Weinberger A. Close association of HLA-B51 and B52 in Israeli patients with Behc¸et’s syndrome. Ann Rheum Dis 1991 ; 50 : 351-9.

12. Brautbar C, Chajek T, Ben-Tuvia S, Lamm L, Cohen T. A genetic study of Behc¸et’s disease in Israel. Tissue Antigens 1978 ; 11 : 113-21.

13. Chung YM, Tsai ST, Liao F, Liu JH. A genetic study of Behc¸et’s disease in Taiwan Chinese. Tissue Antigens 1987 ; 30 : 68-75.

14. Gonzalez-Escribano MF, Rodriguez MR, Walter K, Sanchez-Roman

J, Garcia-Lozano JR, Nu˜nez-Roldan A. Association of HLA-B51 subtypes

and Behc¸et’s disease in Spain. Tissue Antigens 1998 ; 52 : 78-86.

15. Mineshita S, Tian D, Wang LM. Histocompatibility antigens asso- ciated with Behc¸et’s disease in northern Han Chinese. Intern Med 1992 ; 31 : 1073-83.

16. Mizuki N, Ohno S, Tanaka H. Association of HLA-B51 and lack of association of class II alleles with Behc¸et’s disease. Tissue Antigens 1992 ; 40 : 22-33.

17. Yabuki K, Ohno S, Mizuki N. HLA class I and II typing of the patients with Behc¸et’s disease in Saudi Arabia. Tissue Antigens 1999 ; 54 : 273-82.

18. Baricordi OR, Sensi A, Pivetti-Pezzi P. Behc¸et’s disease associa- ted with HLA-B51 and DRw52 antigens in Italians. Hum Immunol 1986 ; 17 : 297-308.

19. Verity DH, Marr JE, Ohno S, Wallace GR, Stanford MR. Behc¸et’s disease, the Silk Road and HLA-B51 : Historical and geographical pers- pectives. Tissue Antigens 1999 ; 54 : 213-21.

20. Gonzalez-Escribano MF, Rodriguez MR, Walter K, Sanchez-Roman J, Garcia-Lozano JR, Nunez-Roldan A. Association of HLA-B51 subtypes and Behc¸et’s disease in Spain. Tissue Antigens 1998 ; 52 : 78-85.

21. Kera J, Mizuki N, Ota M. Significant associations of HLAB* 5101 and B*5108, and lack of association of class II alleles with Behc¸et’s disease in Italian patients. Tissue Antigens 1999 ; 54 : 565-71.

22. Koumantaki Y, Stavropoulos C, Spyropoulou M. HLA-B*5101 in Greek patients with Behc¸et’s disease. Hum Immunol 1998 ; 59 : 250-8.

23. Mizuki N, Ohno S, Ando H. A strong association between HLA- B*5101 and Behc¸et’s disease in Greek patients. Tissue Antigens 1997 ; 50 : 57-62.

24. Yabuki K, Mizuki N, Ota M. Association of MICA gene and HLA- B*5101 with Behc¸et’s disease in Greece. Invest Ophthalmol Vis Sci 1999 ; 40 : 1921-32.

25. De Menthon M, LaValley M, Maldini C, Guillevin L, Mahr A.

HLA–B51/B5 and the risk of Behc¸et’s disease : a systematic review and meta-analysis of case–control genetic association studies. Arthritis Care Res 2009 ; 61 : 1287-96.

26. Choukri F, Chakib A, Himmich H, Sophie H, Sophie CZ. HLA-B*51 and B*15 Alleles confer predisposition to Behc¸et’s Disease in Moroccan Patients. Hum Immunol 2001 ; 62 : 180-5.

27. N. Bennani, O. Atouf, N. Benseffaj, C. Brick, M. Essakalli : HLA polymorphism and Behc¸et’s disease in Moroccan population. Pathol Biol 2008 ; 2724-30.

28. Brick C, Bennani N, Atouf O, Essakalli M. HLA-A, -B, -DR and -DQ allele and haplotype frequencies in the Moroccan population : a general population study. Transfus Clin Biol 2006 ; 13 : 346-52.

29. Izaabel H, Garchon HJ, Caillat-Zucman S, Beaurain G, Akhayat O, Bach JF, et al. HLA class II DNA polymorphism in a Moroccan population from the Souss Agadir area. Tissue Antigens 1998 ; 51 : 106-10.

30. Gómez-Casado E, Del Moral P, Martínez-Laso J, García-Gómez A, Allende L, Silvera-Redondo C, et al. HLA genes in Arabic-speaking Moroccans : close relatedness to Berbers and Iberians. Tissue Antigens 2000 ; 55 : 239-49.

31. Oumhani K, Canossi A, Piancatelli D, Di Rocco M, Del Beato T, Liberatore G, et al. Sequence-Based analysis of the HLA-DRB1 poly- morphism in Metalsa Berber and Chaouya Arabic-speaking groups from Morocco. Hum Immunol 2002 ; 63 : 129-38.

32. Piancatelli D, Canossi A, Aureli A, Oumhani K, Del Beato T, Di Rocco M, et al. Human leukocyte antigen-A, -B, and -Cw polymorphism in a Berber population from North Morocco using sequence-based typing.

Review in Tissue Antigens 2004 ; 63 : 158-72.

33. Choukri F, Chakib A, Himmich H, Raissi H, Caillat-Zucman S. HLA class I polymorphism in a Moroccan population from Casablanca. Eur J Immunogenet 2002 ; 29 : 205-11.

34. Kabbaj M, Mribet M, Oudghiri M, Naaman H, Radouane A El Turk J.

et al. Human leukocyte antigen-A, -B, and -DRB1 : allelic and haplotypic frequencies in a Moroccan population from Casablanca. Ann Biol Clin 2011 ; 69 : In press.

35. Bettencourt A, Pereira L, Carvalho C. New insights of HLA class I association to Behc¸et’s disease in Portuguese patients. Tissue Antigens 2008 ; 72 : 379-82.

36. Ben Ahmed M, Houman H, Abdelhak S. MICA transmembrane region polymorphism and HLA B51 in Tunisian Behcet’s disease patients. Adv Exp Med Biol 2003 ; 528 : 225-8.

37. Gul A, Uyar FA, Inanc M, Ocal L, Barrett JH, Aral O, et al. A weak association of HLA-B*2702 with Behc¸et’s disease. Genes Immun 2002 ; 3 : 368-72.

38. Braakenburg A, De Valk HW, De Boer J, Rothova A. Human leu- kocyte antigen-B27–associated uveitis : long-term follow-up and gender differences. Am J Ophtalmol 2008 ; 145 : 472-9.

39. Meyer JM, Han J, Singh R, Moscley G. Sex influences on the entrance of HLA shared-epitope genotypes for rheumatoid arthritis. Am J Hum Genet 1996 ; 58 : 371-8.

40. Fukazawa T, Yamasaki K, Ito H, Kikuchi S, Minohara M. Both the HLA DPB1 and DRB1 alleles correlate with risk for multiple sclerosis in Japanese : clinical phenotypes and gender as important factors. Tissue Antigens 2000 ; 55 : 199-206.

41. Kabbaj M, Oudghiri M, Naaman H, El Turk J, Bennani S, Hassar M. HLA-A, -B, -DRB1 alleles and haplotypes frequen- cies in Moroccan patients with leukemia. Ann Biol Clin 2010 ; 68 : 291-6.

42. Gebreselassie D, Spiegel H, Vukmanovi´c S. Sampling of MHC

class I-associated peptidome suggests relatively looser global asso-

ciation of HLA-B*5101 with peptides. Hum Immunol 2006 ; 67 :

894-906.