The HLA-A, -B and -DRB1 polymorphism in a large dataset of South Brazil bone marrow donors from Rio Grande do Sul

Human leukocyte antigen (HLA) genes are very informative in population genetics studies and their variability has been widely used to reconstruct the history of geographic and/or demographic expansions of human populations. The characterization of HLA diversity at the population level is also fundamental in clinical studies, particularly for bone marrow transplantation programs. In this study, we investigated the HLA molecular variation in Rio Grande do Sul, South Brazil, in order to identify possible regional differences across this state. More than 97,000 bone marrow donors were typed at the HLA- A, -B and -DRB1 loci and analyzed by considering two kinds of subdivisions based on both self-identified ethnicity and place of residence: (a) the official geographic subdivision defined by the Brazilian Institute of Geography and Statistics and (b) known information about the colonization history of the state. HLA allele and haplotype frequencies were estimated and compared among the defined subgroups. The results indicate a lack of correlation between genetic variation and geography and thus no clear HLA genetic structure based on geographic criteria. On the other hand, major differences were observed regarding ethnicity. In addition, local populations from Rio Grande do Sul were found to be genetically similar to their corresponding parental European populations from Germany, Italy and Portugal, as documented by historical data. Overall, this study provides a thorough characterization of the HLA genetic variation in Rio Grande do Sul and a better understanding of its demographic history, being most useful for the development of more efficient strategies in bone marrow donors' recruitment.

Killer cell immunoglobulin-like receptor (KIR) genes in systemic sclerosis

A previous study has suggested that the combination KIR2DS2(+)/KIR2DL2(-) was related to increased risk for systemic sclerosis (SSc), while others have failed to reproduce this finding. Our objective was to study this matter further and test the association of other KIR genes with SSc. One hundred and ten SSc patients and 115 healthy bone marrow donors were enrolled in a case-control study. Blood was collected for DNA extraction; typing of 15 KIR genes and human leucocyte antigen-C (HLA-C) was made by polymerase chain reaction with sequence specific primers (PCR-SSP), followed by electrophoresis on agarose gel. Patients underwent clinical evaluation, serology, Doppler echocardiography and chest high-resolution computed tomography. The frequency of the inhibitory KIR2DL2 was significantly lower in patients [29.1% versus 65.2% in controls, P < 0.0001; odds ratio (OR) = 0.22, 95% confidence interval 0.12-0.40]. When combinations of activating and inhibitory KIR genes were analysed, the presence of KIR2DS2 in the absence of KIR2DL2 (KIR2DS2(+)/KIR2DL2(-)) was more frequent in patients than in controls (25.5% versus 1.7%, respectively; P < 0.0001; OR = 19.29, 4.24-122.26). However, the presence of both KIR2DS2 and KIR2DL2 (KIR2DS2(+)/KIR2DL2(+)) was more frequent in controls (57.4%) than in patients (28.2%, P < 0.0001), suggesting a preponderant protective effect of KIR2DL2 over KIR2DS2. Stratification for HLA-C1 status did not change these results. No statistically significant associations were found between KIR phenotypes and clinical and laboratory features of SSc. Our results suggest a protective role of KIR2DL2(+) phenotype and confirmed the association of the combination KIR2DS2(+)/KIR2DL2(-) with increased risk for SSc.

A study of the killer cell immunoglobulin-like receptor gene KIR2DS1 in a Caucasoid Brazilian population with psoriasis vulgaris

Psoriasis is a chronic inflammatory skin disease whose pathogenesis and genetic background remain unclear. Considering that previous studies have suggested an association of psoriasis vulgaris (PV) and killer cell immunoglobulin-like receptors (KIRs), we typed 15 KIR genes and human leukocyte antigen (HLA)-Cw in 79 Brazilian Caucasoid patients with PV and 110 healthy controls by polymerase chain reaction (PCR) using sequence-specific oligonucleotides and sequence-specific primers. We did not observe a relevant increase in the frequency of the activating KIR2DS1 gene in the PV group [KIR2DS1, 46 of 79 cases (58.2%) vs 40 of 110 controls (36.4%)]. However, an association of KIR2DS1 with Cw*0602+ in 26.5% of PV patients was observed, while it was present in only 5.4% of controls. These results suggest that activating KIR2DS1 gene may not confer susceptibility to PV, and an association of KIR2DS1 gene with the HLA-Cw*0602+ was observed in these patients.