Alanine at position 73 of HLA-C is associated with psoriasis vulgaris in Finland

ERAP1 and HLA-C*06 are strongly associated with the risk of psoriasis in the population of northern Poland

INTRODUCTION

HLA-C*06 is a major psoriasis genetic risk marker. Recent reports have been focused on the role of different polymorphisms within genes involved in the functioning of the epidermal barrier and antigen processing in the pathogenesis of psoriasis. Data on the association between genetic variants of LCE3B_LCE3C, CSTA, ERAP1, ZAP70 and this dermatosis in the population from Eastern Europe are lacking.

AIM

To compare the association between known genetic risk markers and psoriasis in a cohort of northern Polish patients with psoriasis and healthy controls.

MATERIAL AND METHODS

Based on previous studies' results, five susceptibility loci: HLA-C, LCE3C_LCE3B, ERAP1, ZAP70 and CSTA were selected for genotyping in 148 patients with chronic plaque psoriasis and 146 healthy controls. Each patient with this disease was clinically assessed with the Psoriasis Area and Severity Index.

RESULTS

The study population showed a significant association of psoriasis and a single nucleotide polymorphism in the ERAP1 - rs26653 (p = 3.11 × 10-5) and HLA-C*06 allele (p = 1.02 × 10-11) when compared with the control group. The presence of HLA-C*06 or rs26653 G allele significantly increased the risk of psoriasis by 2.4 times or twice, respectively. Carrying rs26653 C allele considerably decreased the risk of psoriasis by 1.5 times.

CONCLUSIONS

In the context of pathogenesis of psoriasis, our findings might give the evidence on disturbances in the proteolytic processing of N-terminal fragments of antigens presented via major histocompatibility complex class I to T cells.

Evaluation of Psoriasis Genetic Risk Based on Five Susceptibility Markers in a Population from Northern Poland

Psoriasis genetic background depends on polygenic and multifactorial mode of inheritance. As in other complex disorders, the estimation of the disease risk based on individual genetic variants is impossible. For this reason, recent investigations have been focused on combinations of known psoriasis susceptibility markers in order to improve the disease risk evaluation. Our aim was to compare psoriasis genetic risk score (GRS) for five susceptibility loci involved in the immunological response (HLA-C, ERAP1, ZAP70) and in the skin barrier function (LCE3, CSTA) between patients with chronic plaque psoriasis (n = 148) and the control group (n = 146). A significantly higher number of predisposing alleles was observed in patients with psoriasis in comparison to healthy individuals (6.1 vs. 5.2, respectively; P = 8.8×10⁻⁷). The statistical significance was even more profound when GRS weighted by logarithm odds ratios was evaluated (P = 9.9×10⁻¹⁴). Our results demonstrate the developed panel of five susceptibility loci to be more efficient in predicting psoriasis risk in the Polish population and to possess higher sensitivity and specificity for the disease than any of the markers analyzed separately, including the most informative HLA-C*06 allele.

HLA alleles in Brazilian patients with fissured tongue

BACKGROUND

Fissured tongue (FT) is a clinical condition manifested by numerous little furrows on the tongue's surface. Previously, the authors observed an association with HLA-C×06 in psoriasis (PS) and benign migratory glossitis (BMG); however, HLA-C was not surveyed in FT.

OBJECTIVE

This study investigated the association between HLA alleles and FT.

METHODS

Thirty-three FT bearers were studied, after evaluation of criteria for inclusion. These patients did not present PS, BMG or any other conditions associated with FT. The control group (CG) was composed of 561 individuals with HLA-A, 560 individuals with HLA-B, 168 individuals with HLA-C, 564 individuals with HLA-DRB1 and 390 individuals with HLA-DQB1. Samples from these individuals were processed to extract DNA. The HLA classes I and II were determined using the reverse line blot technique. The frequencies of HLA antigens found in patients were compared with the CG using Fisher's exact test.

RESULTS

The comparison of the frequencies of HLA antigens found in the patient groups and in CG revealed no association with any of the alleles studied, except for HLA-A*01, which exhibited a decreased frequency in patient groups. HLA-C*06 was detected in 7.57% of FT patients and 10.42% of the CG (not significant).

CONCLUSION

The lack of association of FT with HLA-C*06 reinforces the proposal that this disease does not have a common genetic factor in the triad of BMG, FT and PS.

Haplotype associations of the MHC with psoriasis vulgaris in Chinese Hans

Summary Haplotype associations of the major histocompatibility complex (MHC) with psoriasis vulgaris (PV) have been demonstrated in different racial or ethnic populations. The objective of this study was to demonstrate the different haplotype associations of the MHC in Chinese patients with psoriasis according to the type of onset and their sex. One hundred and thirty-eight patients with PV and 149 normal control subjects without psoriasis were typed for HLA-A, -B, -C, -DQA1, -DQB1 and -DRB1 by using the PCR with sequence-specific primers. The results showed: (i) HLA-A*26 (26.1% vs. 12.1%, Pc < 1 x 10(-5)), -B*27 (17.03% vs. 1.01%, Pc < 1 x 10(-7)), -Cw*0602 (15.58% vs. 5.03%, Pc < 1 x 10(-2)), -DQA1*0104 (19.93% vs. 9.40%, Pc < 1 x 10(-3)), -DQA1*0201 (22.40% vs. 10.74%, Pc < 1 x 10(-3)), -DQB1*0303 (18.12% vs. 9.73%, Pc < 1 x 10(-7)), and -DRB1*0701/02 (26.09% vs. 9.73%, Pc < 1 x 10(-7)) were significantly increased in PV patients, while HLA-B*57, -DQB1*0201 were slightly increased in PV patients. HLA-Cw*0304 (5.07% vs. 14.43%, Pc < 1 x 10(-3)), -DQA1*0501 (5.79% vs. 14.09%, Pc < 0.05) were found to be negatively associated with PV, but HLA-A*2 (2.54% vs. 6.38%, Pc < 0.5) was decreased in PV patients without statistical significance. (ii) HLA-A*26-B*27 [P < 0.0001, odds ratio (OR) = 48.38], -A*26-Cw*0602 (P < 0.0001, OR = 11.84), -B*27-Cw*0602 (P < 0.0001, OR = undefined), -DRB1*0701/02-B*27 (P < 0.0001, OR = 22.62), -DRB1*0701/02-DQA1*0104 (P < 0.0002, OR = 3.59), -DRB1*0701/02-DQB1*0303 (P < 0.0001, OR = 5.63), -DQA1*0201-DQB1*0303 (P < 0.0002, OR = 7.77), -A*26-B*27-Cw*0602 (P < 0.0004, OR = undefined), -A*26-DRB1*0701/02-DQA1*0201-DQB1*0303 (P < 0.01, OR = undefined) were identified as risk haplotypes for patients with PV in China. (iii) HLA-A*26 -B*27 (P < 0.0001, OR = 58.47), -DQA1*0201-DQB1*0303 (P < 0.0001, OR = 8.62), -DRB1*0701/02 -DQA1*0104 (P < 0.0002, OR = 4.13), -DRB1*0701/02-DQB1*0303 (P < 0.0001, OR = 6.68) and -A*26-DRB1*0701-DQA1*0201 -DQB1*0303 (P < 0.006, OR = undefined) were only significantly associated with type I psoriasis compared with controls, while others showed no differences in either type I or type II psoriasis. (iv) These associated haplotypes with PV were not different by sex, except that the frequency of DRB1*0701/02-DQB1*0303 (P < 0.0001, OR = 10.14) was higher in male patients with psoriasis. To summarize, this study demonstrated a differential association of HLA and identified some special risk haplotypes in Chinese patients with PV compared with other ethnic or racial populations.

Strong association of HLA-Cw6 allele with juvenile psoriasis in Polish patients

Association of psoriasis vulgaris with HLA-C is not equally strong in different human populations. It has not yet been studied in Polish patients at DNA level, but only by serology that is inadequate for HLA-C. Therefore, we examined the distribution of HLA-C alleles by means of low resolution PCR-SSP in 102 Polish psoriatics and 123 healthy controls. We have found significantly higher representation of HLA-Cw*06 (odds ratio, 18.73; P(cor)<0.001) and significantly lower representation of HLA-Cw*07 (odds ratio, 0.41; P(cor)<0.038) in patients than in controls. Association of HLA-Cw*06 with psoriasis was even stronger in early age at onset (0-20 years) group: odds ratio, 77.71; P(cor)<0.001. Therefore, our population seems to belong to those with strong association of psoriasis with HLA-Cw*06.

The OTF3 gene polymorphism confers susceptibility to psoriasis independent of the association of HLA-Cw*0602

Psoriasis has been strongly associated to HLA-Cw6, but it remains unclear whether Cw6 itself or a closely linked gene is associated with the disease. The aim of this study was to clarify whether the HLA-C itself determines disease susceptibility or whether it acts only as a marker for the susceptibility allele. We examined a sample of 95 type I psoriasis patients and 104 Spanish matched controls to investigate whether HLA-Cw*0602 or other closely related class I loci, such as HLA-B and MICA (which are centromeric to HLA-C), or corneodesmosin gene and octamer transcription factor-3 genes (which are telomeric to HLA-C), might play a part in disease development. DNA samples were genotyped by polymerase chain reaction/sequence-specific primers (HLA-C), polymerase chain reaction/sequence-specific primers (HLA-B), radioactive polymerase chain reaction (MICA-TM polymorphism in the transmembrane region), and polymerase chain reaction/restriction fragment length polymorphism (protein S and octamer transcription factor-3). Our results show a significant increase of Cw*0602 in psoriasis patients (odds ratio = 3.64; pc < 0.0006). A significant association between the beta allele of octamer transcription factor-3 (HindIII) and psoriasis was also detected (odds ratio = 3.76; pc < 0.0003). The allele octamer transcription factor-3B (etiologic fraction = 0.62) was found to be more strongly associated to psoriasis vulgaris than Cw*0602 (etiologic fraction = 0.35) and the increase of octamer transcription factor-3 B allele is independent of the linkage disequilibrium with Cw*0602 as this was also found in Cw*0602 negative patients (odds ratio = 3.63; pc < 0.015, etiologic fraction = 0.55). We did not detect an association between the corneodesmosin gene and psoriasis. This fact suggests that the psoriasis susceptibility gene is located within a critical region of 147 kb, telomeric to HLA-C and centromeric to the corneodesmosin gene, and the association of Cw6 to psoriasis may be secondary to linkage disequilibrium.

The A5.1 allele of the major histocompatibility complex class I chain-related gene A is associated with psoriasis vulgaris in Chinese

BACKGROUND

Recent studies have demonstrated an association of a polymorphic (GCT)n triplet repeat in the transmembrane (TM) region of the major histocompatibility complex (MHC) class I chain-related gene A (MICA), one of the MHC class I chain-related (MIC) family members, with some autoimmune diseases, including Behçet's disease, acute anterior uveitis, Takayasu's arteritis and others.

OBJECTIVES

The aim of this study was to examine whether the MICA gene is associated with psoriasis vulgaris (PS) in Chinese.

PATIENTS AND METHODS

The (GCT)n polymorphism of the MICA gene was investigated in 200 healthy Chinese of Han origin and 300 patients with PS by polymerase chain reaction amplification and denaturing polyacrylamide gel electrophoresis.

RESULTS

Five alleles, namely A4, A5, A6, A9 and A5.1 were found in both groups. Comparison of the data from both groups revealed that the A5.1 allele was present at a significantly higher frequency in the patient group (41.5%) than in the control group (23.0%) (Pc < 0.0001, Pc means the probability of a comparison with the control group). The frequency of A5.1-positive cases was also significantly increased in the patient group (68.0%) as compared with the controls (38.0%) (Pc < 0.0001). Furthermore, the carrier frequency of A5.1-positive was significantly increased in psoriatic patients with a positive family history and with early onset as compared with sporadic cases (Pc = 0.0005) and with late onset PS (Pc = 0.002).

CONCLUSIONS

These results suggest that the MICA gene may be associated with the development of PS in Chinese.

PERB11 (MIC): a polymorphic MHC gene is expressed in skin and single nucleotide polymorphisms are associated with psoriasis

The susceptibility genes for psoriasis remain to be identified. At least one of these must be in the major histocompatibility complex (MHC) to explain associations with alleles at human leucocyte antigen (HLA)-A, -B, -C, -DR, -DQ and C4. In fact, most of these alleles are components of just two ancestral haplotypes (AHs) designated 13.1 and 57.1. Although relevant MHC gene(s) could be within a region of at least 4 Mb, most studies have favoured the area near HLA-B and -C. This region contains a large number of non-HLA genes, many of which are duplicated and polymorphic. Members of one such gene family, PERB11.1 and PERB11.2, are expressed in the skin and are encoded in the region between tumour necrosis factor and HLA-B. To investigate the relationship of PERB11.1 alleles to psoriasis, sequence based typing was performed on 97 patients classified according to age of onset and family history. The frequency of the PERB11.1*06 allele is 44% in type I psoriasis but only 7% in controls (Pc = 0.003 by Fisher's exact test, two-tailed). The major determinant of this association is a single nucleotide polymorphism (SNP) within intron 4. In normal and affected skin, expression of PERB11 is mainly in the basal layer of the epidermis including ducts and follicles. PERB11 is also present in the upper keratin layers but there is relative deficiency in the intermediate layers. These findings suggest a possible role for PERB11 and other MHC genes in the pathogenesis of psoriasis.

The association of psoriasis with human leukocyte antigens in Korean population and the influence of age of onset and sex

To identify HLA markers that may contribute to the genetic susceptibility of Koreans to psoriasis, we studied 84 psoriasis patients, with serologic HLA types of A, B, and genotypes of HLA-Cw, DRB1, DQA1, DQB1, DPB1 alleles. The distribution of HLA markers and the associated haplotypes were analyzed according to age and sex. HLA-Cw*0602 showed the strongest association with psoriasis (relative risk = 36.0, p < 10-8, Pc < 8 x 10-7). The frequencies of A1 (relative risk = 17.0, p < 9 x 10-7, Pc < 7 x 10-5), A30 (relative risk = 5.5, p < 2 x 10-5, Pc < 0.001), B13 (relative risk = 5.6, p < 4 x 10-6, Pc < 3 x 10-4), B37 (relative risk = 30.3, p < 7 x 10-7, Pc < 6 x 10-5), DRB1*07 (relative risk = 5.9, p < 2 x 10-6, Pc < 8 x 10-5), DRB1*10 (relative risk = 26.4, p < 4 x 10-6, Pc < 3 x 10-4), DQA1*02 (relative risk = 6.2, p < 5 x 10-7, Pc < 4 x 10-4), DQB1*02 (relative risk = 2.5, p < 0.005, Pc = ns) and DPB1*1701 (relative risk = 24.6, p < 9 x 10-6, Pc < 7 x 10-4) were also significantly increased in Korean psoriasis patients. Type I and type II psoriasis were subdivided into groups of below and above 30 y of age, because of the significant difference found in HLA-Cw*0602 phenotype frequency between the two groups (83.9% vs. 54.5%, p < 0. 009). In addition to HLA-Cw*0602, the frequencies of B37 and DPB1*1701 were significantly higher in type I as opposed to type II psoriasis. HLA-A30-B13-Cw*0602-DRB1*07-DQA1* 02-DQB1*02 was identified as a high risk haplotype. This was particularly true at an early age in the female. HLA-A33-B44-Cw*1401-DRB1*13-DQA1* 01-DQB1*06-DPB1*0401 was defined as a protective haplotype for psoriasis. The extended haplotype HLA-A1-B37-Cw*0602-DRB1*10-DQA1*01-DQB1*05 was discovered to be a high-risk factor in Koreans. To summarize, this study demonstrates the differential association of HLA according to sex, and identifies a newly found high-risk haplotype and a protective haplotype in Korean psoriasis patients.

HLA-C high resolution typing: analysis of exons 2 and 3 by sequence based typing and detection of polymorphisms in exons 1-5 by sequence specific primers

HLA-C high resolution sequence based typing developed in this study involves a unique DNA amplification encompassing exon 1 to intron 3 and four fluorescent sequencing reactions covering exon 2 and 3. Both dye primer and dye terminator sequencing techniques were performed and results compared. This approach allowed the identification of all of the 50 HLA-C allelic variants so far described, except for two allele pairs that are distinguished by non-coding nucleotide changes (Cw*12021 = 12022, Cw*15051 = 15052) and three allele pairs (Cw*0701 = 706, Cw*1701 = 1702 and Cw*1801 = 1802) that share the same nucleotide sequence in exon 2 and 3. For complete subtyping of these allelic variants, an amplification based on sequence specific primers (PCR-SSP) was used. No ambiguous heterozygous combinations of alleles were detected in our panel so far. HLA-C typing data obtained by this method were compared with data from serological and low resolution PCR-SSP typing, which had been performed previously on the samples sequenced.

HLA class I and II alleles and susceptibility to generalized pustular psoriasis: significant associations with HLA-Cw1 and HLA-DQB1*0303

HLA alleles in generalized pustular psoriasis (GPP) were investigated to clarify the etiology and/or pathogenesis of this disease. Not only serological typing of HLA class I and II antigens but also genotyping of HLA class II alleles were carried out in twenty-six unrelated Japanese patients with GPP. These patients were classified according to their history of psoriasis vulgaris (PV). Serological typing revealed a significantly high incidence of HLA-Cw1 (Pc = 0.04) in the patients as compared with Japanese healthy controls. The frequency of HLA-B46 was particularly high in the patients with GPP and a previous history of PV. Genotyping of HLA class II alleles showed a highly significant increase in HLA-DQB1*0303 (Pc = 0.01) in the patients vs. the healthy controls. In particular, HLA-DQB1*0303 was significantly more frequent in the patients with no prior history of PV than in those with a history of PV. Analysis on linkage disequilibrium showed remarkably different patterns for HLA class II haplotypes between the patients and the healthy controls. Based on the comparative analysis among the amino acid sequences of the beta 1-domain of the HLA-DQB1*03 alleles, proline at residue 55 was suggested to be important as a common amino acid for determination of the susceptibility to GPP. These results revealed not only an association between the etiology and/or pathogenesis of GPP and HLA, but also different mechanisms of the immune response between the patients with GPP and PV.

The complete genomic sequence of 424,015 bp at the centromeric end of the HLA class I region: gene content and polymorphism

We report here the genomic sequence of the centromeric portion of HLA class I, extending 424,015 bp from tumor necrosis factor alpha to a newly identified gene approximately 20 kb telomeric of Otf-3. As a source of DNA, we used cosmids centromeric of HLA-B that had been mapped previously with conventional restriction digestion and fingerprinting and previously characterized yeast artificial chromosomes subcloned into cosmids and mapped with multiple complete digest methodologies. The data presented provide a description of the gene content of centromeric HLA class I including new data on intron, promoter and flanking sequences of previously described genes, and a description of putative new genes that remain to be characterized beyond the structural information uncovered. A complete accounting of the repeat structure including abundant di-, tri-, and tetranucleotide microsatellite loci yielded access to precisely localized mapping tools for the major histocompatibility complex. Comparative analysis of a highly polymorphic region between HLA-B and -C was carried out by sequencing over 40 kb of overlapping sequence from two haplotypes. The levels of variation observed were much higher than those seen in other regions of the genome and indeed were higher than those observed between allelic HLA class I loci.

Role of HLA-B and C alleles in development of psoriasis in patients from North India

The association of HLA antigens with susceptibility for development of psoriasis vulgaris has been studied mostly using serologic methods. A number of different HLA class I antigens have been reported to be associated with predisposition to develop this disease. While Cw6 is the allele most commonly thought to confer risk for psoriasis, a number of HLA-B locus alleles have also been thought to be involved and, recently, in at least three studies, a specific amino acid in the HLA-C heavy chain has been implicated. With the recent development of molecular methods for typing for HLA class I alleles, it has become possible to re-examine this association by performing high resolution typing. In the present study we have investigated 38 psoriasis patients and 84 ethnically and geographically matched controls from North India. They were typed for HLA-B and HLA-C. The results showed the Cw*0602 was the main allele that was increased in this group of patients. The previously reported association with alanine-73 was not found to be significant. Cw*0602 was found in 71% of the patients. B*5701 and B*3701 were also increased but appeared to be secondary to linkage disequilibrium with Cw*0602.

HLA-CW*0602 is a susceptibility factor in type I psoriasis, and evidence Ala-73 is increased in male type I psoriatics

We investigated the HLA-C locus of 87 unrelated patients with chronic plaque psoriasis by genotyping with sequence-specific amplification primers. The HLA-Cw*0602 allele was significantly increased in male and female type I psoriatics but not significantly increased in either male or female type II psoriatics. The overall frequency of Ala-73 (present in Cw*04, Cw*0602, Cw*07, Cw*12, Cw*1503, and Cw*17) in psoriatics was 88.5% but the incidence of Ala-73 in our Caucasian controls was also high at 84.3%. Ala-73 was present in 97.2% of type I and 85.7% of type II male psoriatics (chi2 = 8.43, p = 0.001; chi2 = 0.01, p = nonsignificant, respectively), in contrast to 81.5% of type I and 80% of type II female psoriatics (nonsignificant). HLA-Cw*0602 appeared more discriminating in determining disease susceptibility in our population than Ala-73, in line with earlier serologic studies implicating HLA-Cw6. Thus, although the frequency of HLA-Cw*0602 decreased from 54.0% in type I to 29.2% in type II psoriatics, the overall frequency of Ala-73, present in 90.4% of type I and 83.3% of type II psoriatics, did not. (i) Thus this study confirms the strong association between psoriasis and HLA-Cw*0602 by using sequence-specific amplification primers. (ii) Results show that Ala-73 on HLA-C molecules is increased in frequency in psoriasis, but results observed show an association more subtle than previously thought, with HLA-Cw*0602 playing the major role. (iii) This report documents the differential association of HLA genes in male and female psoriatic patients. An interaction between gender and immunogenetics may influence susceptibility to psoriasis.

High resolution HLA-C typing by PCR-SSP: identification of allelic frequencies and linkage disequilibria in 604 unrelated random UK Caucasoids and a comparison with serology

Recent evidence indicates that HLA-C molecules are biologically relevant by eliciting T-cell responses and exerting control over NK cell function. In addition, HLA-C is associated with susceptibility to various diseases, notably psoriasis vulgaris. Clarification of the full biological roles for HLA-C has however proved difficult because detection of HLA-C antigens by complement mediated cytotoxicity using alloantisera is inefficient. Up to 50% of individuals in every race have serologically undetectable HLA-C locus antigens due to a combination of relatively low expression, lack of serological reagents and a lack of information about the distribution of the HLA-C blank alleles. Recently, amplification of DNA using sequence-specific primers (PCR-SSP) has proved a reliable, accurate and rapid method for medium resolution HLA-C typing. We have now developed high resolution HLA-C typing by PCR-SSP utilizing allele and group-specific PCR-SSP reactions which can identify all HLA-C alleles (except non-coding change alleles) in most heterozygous combinations. Using this system we have typed 604 unrelated United Kingdom Caucasoids to generate accurate frequency and linkage disequilibrium data. To assess the validity of serology for HLA-C, PCR-SSP typings for 527 out of the 604 individuals were compared to serology. We find that the frequency of many HLA-C antigens has been underestimated by serology and some antigens such as Cw6 are consistently assigned incorrectly by serology. The overall discrepancy rate between serology and SSP was high at 37% (195/527). High-resolution HLA-C typing of 112 International Histocompatibility Workshop cell lines has also been performed.

HLA-C revisited. Ten years of change

During the past 10 years knowledge about the interactions between major histocompatibility complex (MHC) class I molecules and the T-cell receptor (TCR) complex of cytotoxic T-cells (CTL) has developed dramatically. But the primary interest, both with respect to structure as well as function, has concentrated on HLA-A and -B molecules because of their high sequence polymorphism and their dominating presence at the cell surface. In contrast, HLA-C molecules seemed to be of only minor importance in the cascade of immune reactions owing to their more limited polymorphism and reduced levels of surface expression. The inability to define a number of antigen specificities had the result that HLA-C molecules were often neglected in studies of immune response, transplantation, and disease association. More recently a new function has been identified for HLA class I molecules where they act as inhibitors of the lytic capacity of natural killer (NK) cells and non-MHC-restricted T-cells. Moreover, the understanding of this novel mode of negative regulation of cytotoxicity was remarkably influenced by HLA-C since these were the first HLA class I molecules found to have such inhibitory potential. With this new inhibitory function serving as an essential component of the immune system, HLA-C molecules can no longer be neglected.

High resolution HLA-C typing by PCR-SSP: identification of allelic frequencies and linkage disequilibria in 604 unrelated random UK Caucasoids and a comparison with serology

Recent evidence indicates that HLA-C molecules are biologically relevant by eliciting T-cell responses and exerting control over NK cell function. In addition, HLA-C is associated with susceptibility to various diseases, notably psoriasis vulgaris. Clarification of the full biological roles for HLA-C has however proved difficult because detection of HLA-C antigens by complement mediated cytotoxicity using alloantisera is inefficient. Up to 50% of individuals in every race have serologically undetectable HLA-C locus antigens due to a combination of relatively low expression, lack of serological reagents and a lack of information about the distribution of the HLA-C blank alleles. Recently, amplification of DNA using sequence-specific primers (PCR-SSP) has proved a reliable, accurate and rapid method for medium resolution HLA-C typing. We have now developed high resolution HLA-C typing by PCR-SSP utilizing allele and group-specific PCR-SSP reactions which can identify all HLA-C alleles (except non-coding change alleles) in most heterozygous combinations. Using this system we have typed 604 unrelated United Kingdom Caucasoids to generate accurate frequency and linkage disequilibrium data. To assess the validity of serology for HLA-C, PCR-SSP typings for 527 out of the 604 individuals were compared to serology. We find that the frequency of many HLA-C antigens has been underestimated by serology and some antigens such as Cw6 are consistently assigned incorrectly by serology. The overall discrepancy rate between serology and SSP was high at 37% (195/527). High-resolution HLA-C typing of 112 International Histocompatibility Workshop cell lines has also been performed.

Study of aspartate at residue 9 of HLA-C molecules in Japanese patients with psoriasis vulgaris

The frequency of aspartate at residue 9 (Asp-9) of HLA-C molecules was investigated among 75 Japanese patients with psoriasis vulgaris and 50 healthy controls. We developed a technique of polymerase chain reaction sequence-specific primer (PCR-SSP) amplification of genomic DNA for HLA-C alleles with a codon for Asp-9. The specificity of amplification was confirmed by direct sequencing of the amplified products and amplification from total RNA (RT-PCR). Asp-9 was positive in all individuals with Cw6 and/or Cw7, but negative in the others, indicating that Asp-9 was specific to Cw6 and Cw7 antigens in our subjects. The frequency of Asp-9 was significantly increased in the patient group (48% vs. 20%; P < 0.002). The frequency of alanine at residue 73 (Ala-73), which was positive for Cw4, Cw6, Cw7, and some C blanks, was also increased in our previous study (81% vs. 48%; P < 0.0001). Asp-9 is located on a beta sheet of alpha 1 domain of HLA-C molecule and influences the peptide binding of the C pocket of the groove together with Ala-73. Both Asp-9 and Ala-73 could contribute to the disease susceptibility to psoriasis vulgaris in the immune responses.

HLA risk haplotype Cw6,DR7,DQA1*0201 and HLA-Cw6 with reference to the clinical picture of psoriasis vulgaris

Psoriasis vulgaris has HLA associations. We have previously defined HLA-Cw6,DR7,DQA1*0201 as the central element of the risk haplotypes for psoriasis. On the other hand, Cw6 as a single gene has the strongest association with psoriasis. The aim of this study was to determine whether the risk haplotype and Cw6 correlate with the clinical parameters of the disease. The series consisted of 64 patients and the clinical parameters were age at onset, family history of psoriasis, arthritis and the frequency of inpatient treatment. The HLA risk haplotype Cw6,DR7,DQA1*0201 had previously been found in 30% and Cw6 alone in 54% of the patients. The presence of Cw6 correlated with early age at onset (Pc = 0.01). The presence of the risk haplotype correlated with a positive family history of psoriasis among the first-degree relatives (Pc = 0.02) and an overall positive family history (Pc = 0.04), but Cw6 had a stronger correlation with an overall positive family history (Pc = 0.01). There were no positive correlations with arthritis or the number of inpatient treatment periods. Only type I psoriasis was associated with Cw6 (Pc = 0.0006). In conclusion, Cw6 and the haplotype Cw6,DR7,DQA1*0201 are important in the heredity of psoriasis vulgaris, but the presence of Cw6 alone is sufficient to indicate a clinically significant risk for psoriasis.

Immunogenetic profile of psoriasis vulgaris: association with haplotypes A2,B13,Cw6,DR7,DQA1*0201 and A1,B17,Cw6,DR7,DQA1*0201

Psoriasis vulgaris is a skin disease with an immunological and genetic background present in 1-3% of the population. We studied the genetic susceptibility to psoriasis vulgaris in Finns with serological HLA typing and genomic HLA class II typing of the DQ and DP loci to evaluate the risk of developing psoriasis. The haplotypes most frequently distinguishing between psoriatics and controls were those that carried Cw6 (P < 10(-8)), DQA1*0201 (P = 9.3 x 10(-6)) and DR7 (P = 3.9 x 10(-5)). The two most frequent marker haplotypes were A2,B13,Cw6,DR7, DQA1*0201 and A1,B17,Cw6,DR7,DQA1*0201, which were not found among the control subjects. A deficit of haplotype B8,DR3,DQ2 (2 out of 124 in the patients versus 15 out of 106 in the controls, P = 1.5 x 10(-4)) was found, and this was in accordance with a slightly decreased frequency of DQA1*0501 (P = 3.1 x 10(-2)), which was usually linked with this haplotype. These results stimulate the research for a genetic resistance factor in psoriasis. Thus, this report sheds further light on the immunogenetic background of psoriasis in Finland. We conclude that the inheritance of psoriasis has a polygenic mode, in which the Cw6,DR7,DQA1*0201 combination seems to be important (P = 7.5 x 10(-7), relative risk 24.4, aetiological factor 0.29).