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Objective: The aim of the study was to investigate association between HLA class II alleles and juvenile idiopathic arthritis (JIA) in Mexican patients., Patients and Methods: We typed 120 patients with JIA and 99 healthy controls for HLA class II alleles were performed by PCR-SSO. Differences between the whole group of JIA and its subtypes and controls were calculated by using the Xi2; p-values were corrected (pc) with Bonferroni's test., Results: The alleles HLA-DRB1*01 (pc= 0.00083) and HLA-DRB1*04 (pc=0.0049) were strongly associated with systemic JIA, while HLA-DRB1*11 and HLA-DRB1*14 were found to have decreased frequencies in the patients with systemic JIA compared to the controls. Two alleles were found to have increased frequencies with JIA oligoarthritis subgroup, HLA-DRB1*11 (p=0.01, pc=NS) and HLA-DRB1*13 (p=0.01, pc=NS). The HLA-DRB1*04 was found increased frequencies with susceptibility for RF negative and RF positive polyarthritis JIA subgroups (p correction resulted in loss of significance). In contrast two alleles HLA-DRB1*07 and HLA-DRB1*14 were found decreased frequencies only patients RF positive polyarthritis JIA subgroup compared to the controls (pc=NS)., Conclusion: The profile of HLA-DRB1 alleles associations in Mexican with JIA were somewhat distinct from association typically found in Caucasians.

Objective: To describe the association between HLA-B and HLA-DR genes and juvenile onset spondyloarthritides (SpA) in Mexicans., Methods: The study included 66 consecutive patients with SpA (45 with ankylosing spondylitis (AS) and 21 with undifferentiated SpA) and 99 non-related healthy controls. The HLA-A, -B and DR alleles were detected by the polymerase chain reaction with the sequence-specific primers technique. Statistical methods included the Mantel-Haenzel chi2 test, Fisher's exact test, and Woolf method for odds ratio (OR)., Results: The frequency of HLA-B27 was significantly increased in the whole group (pC < 10(-3), OR = 53.0, aetiological fraction = 51%), particularly in AS (pC < 10(-3), OR = 67.42, aetiological fraction 57%). In contrast, the frequencies of HLA-B44, and HLA-B14 were significantly decreased. Also, a weak negative association HLA-DR5 (p < 0.05) was found., Conclusion: Apart from an expected significant association between HLA-B27 and juvenile-onset SpA, particularly AS, we found negative associations with HLA-B44, B14, and DR5. There was also a trend for HLA-B15 and DR1 associations with SpA.

Objective: The aim of this study was to analyze the frequencies of the CCR5 delta 32 deletion and HLA class II alleles in Mexican Amerindian populations and its relevance in the development and severity of RA., Methods: We studied 212 Mexican Mestizo subjects (40 patients with refractory RA, 102 patients with non-refractory RA and 70 healthy individuals). At the same time, to evaluate the ethnicity of the CCR5 delta 32 deletion we also studied 192 individuals from three Mexican Amerindian populations (70 Mayo (Capomo) individuals, 61 Teenek individuals, and 61 Mazatecan Indians). The delta 32 deletion in the CCR5 structural gene and HLA-DRB1 were determined by a PCR-SSP and a PCR-SSO procedure, respectively., Results: In the non-refractory RA group the CCR5 delta 32 gene frequency was 0.019 and the following genotype frequencies were observed: CCR5/CCR5 = 98.0%, CCR5/CCR5 delta 32 = 1.9% and CCR5 delta 32/CCR5 delta = 1.0%. In the refractory RA group the CCR5 delta 32 gene frequency was 0.025 and the genotype distribution was similar to that in the non-refractory RA group. The deletion was not detected in the Mexican Mestizo healthy group, or among the Teenek and Mayo Amerindians, all being individuals homozygous for the wild type allele. In the Mazatecan group the deletion frequency was 1.6% (g.f. = 0.016). We observed a significant increase in the frequency of the DRB1*07 allele in severe RA patients in relation to the non-severe RA group (p = 0.02, OR = 5.65, 95% CI = 0.95-43.05)., Conclusion: Our results suggest that the CCR5 delta 32 deletion is not common in Mexican Amerindian populations and this study does not support an important role of CCR5 delta 32 in the pathogenesis of RA or a severe form of the disease in Mexicans.

Objective: The aim of the present work was to study the association between HLA alleles and Takayasu's arteritis in Mexican Mestizo patients., Methods: The study included 26 Mexican Mestizo patients with Takayasu's arteritis and 99 healthy unrelated individuals. HLA-A, -B and -DR alleles were determined by polymerase chain reaction PCR-SSP RESULTS: Increased gene frequencies were demonstrated for HLA-B15(p=0.009,pC=0.020,OR=3.24,EF=11.9%) and HLA-B52 (p=0.008, pC=0.027, OR=5.16, EF=7.7%), and a decreased frequency for the HLA-A24 allele in patients compared to normal controls (p=0.035, pC=NS, PF=11.1%). When HLA typing was correlated to clinicalfeatures in 24 cases, wefound an increasedfrequencies of HLA-DR14 in patients with systemic arterial hypertension (p=0.005, pC=0.004, OR=24.6, EF=38.3%) and HLA-A2 on patients with pulmonary involvement (p=0.034, pC=0.036, OR=3.67, EF=40.4%) when compared to patients without these clinical manifestations., Conclusion: These data confirm HLA-B52 as a relevant susceptibility allele for Takayasu's arteritis and suggest that HLA-B15 could be important as a marker of the disease in Mexican patients. Other class I and/or class II alleles could also be relevant as markers for the clinical features present in these patients.

Objective: The aim of this study was to determine the HLA antigens in Mexican Mestizo patients with mixed connective tissue disease (MCTD)., Methods: We studied 30 patients with MCTD and 99 healthy controls. HLA-A, -B, and -DQ antigens were typed by microlymphocytotoxicity assays. DRB1, DQA1 and DQB1 alleles were oligotyped., Results: HLA-A2 and HLA-B35 were the most frequent MHC class I alleles in MCTD patients, although they were not statistically more frequent than in the controls. According to serological tests, the most frequent DQ allele in the patients was DQ1, which was statistically increased when compared with controls (p = 0.0051). By oligotyping, the DR1 allele and the DQB1*0501 specificities were significantly increased in the patients vs. controls (p = 0.032 and 0.027, respectively)., Conclusion: The elevated levels of DQ1 found in Mexican MCTD patients, although weak, may indicate a particular genetic susceptibility, since there are previous reports of associations of other alleles (such as DR4) with MCTD in other populations. The increase in DQB1*0501 may account for the increase in DQ1. DQB1*0501 has also been reported in black patients with anti-RNP autoantibodies, compared with black patients without anti-RNP or anti-Sm.

Objective: To study the association between Major Histocompatibility Complex (MHC) haplotypes and systemic sclerosis (SSc) in Mexican mestizo patients., Methods: Class I, II and III MHC antigens were determined in 41 Mexican mestizo patients with SSc, 113 of their first degree relatives, and 85 ethnically matched controls. The significance of differences between patients and controls was tested by chi-square analysis with Yates' correction., Results: Frequencies of HLA-DR5 and HLA-DRw52 were found to be higher in SSc patients compared to ethnically matched healthy controls (p = 0.007, RR = 3.31; 95% confidence interval: 1.3-8.3 and p = 0.04, RR = 2.4; 95% confidence interval: 1.0-5.7, respectively). Sequence-specific oligotyping in DR5 positive individuals showed that 10 out of 41 patients had the DRB1*1104 subtype (24.3%) as compared to only 6 of the 85 healthy controls (7.0%) (p = 0.01, RR = 4.25). Subdividing patients according to their clinical features showed a significant increase of HLA-DR5 in diffuse (p = 0.013, RR = 3.89, 95% confidence interval: 1.27-12.0) and limited scleroderma (p = 0.0008), but not in the CREST syndrome. Segregation analysis obtained from the families showed that in the patients, DR5 was mostly part of the [HLAB35;DR5] haplotype as opposed to healthy controls., Conclusion: These data support the role of DR5 (DRB1*1104) in the genetic susceptibility to develop scleroderma in Mexican patients and also sustain the notion of genetically determined clinical subgroups of SSc.

Objective: We studied the gene frequencies of classes I, II and III antigens of the Major Histocompatibility Complex (MHC) in 32 Mexican mestizo patients with rheumatoid arthritis (RA) and compared them with those obtained from 110 of their first degree relatives and 100 Mexican mestizo controls. Furthermore, we analyzed the observed and expected frequencies of the haplotypes and calculated the delta values in the three groups., Methods: The class I and class II MHC antigens were determined by the microlymphocytotoxicity test; class III MHC antigens were obtained by high voltage agarose gel electrophoresis and immunofixation. The significance of differences among the three groups was tested by chi-square analysis; linkage disequilibrium among the different alleles in each haplotype was estimated by computing the delta values (observed vs expected frequencies)., Results: Patients showed a significantly increased frequency of HLA-A1 (corrected p = 10(-5)), DR3 (corrected p = 0.04) and DQ2 (corrected p = 10(-4)) and a decreased frequency of A31 (corrected p = 0.003) as compared to the normal controls. First degree relatives compared to patients and controls showed a decreased frequency of HLA-DR4 (corrected p = 0.02 and 0.008 respectively); consequently, DQ3 was also diminished (corrected p = 10(-4)). Analysis of MHC haplotypes within families revealed in the patients seven MHC haplotypes with significant differences between the observed and expected frequencies (statistically significant delta values). These haplotypes were: [HLA-B8; DR3], [HLAB44; FC31], [HLA-B8; SC42], [HLA-DR4; SC31], [HLA-B35; SC32], [HLA-DR7; FC31] and [HLA-DR2; SC31]. On the other hand, the control haplotypes showed significant delta values in only one of these haplotypes ([HLA-DR4; SC31]), whereas first degree relatives showed none. Analysis of all the class I, II and III alleles, either alone or as part of specific haplotypes, showed two B-DR haplotypes with higher relative risks than their alleles alone. These haplotypes were: [B44; DR4] (RR = 6.0, p = 0.005), and [B8; DR3] (RR = 8.3, p = 0.010)., Conclusion: The results suggest that a specific combination of antigens in the same haplotype (for instance between HLA-B and HLA-DR) could contribute to increasing the genetic susceptibility to develop RA.