DR4 Gene Research Articles

Characterization of the Resistance Mechanisms of HL60 Leukemia Cell Derivatives to Apo2L/TRAIL.

Tumor necrosis factor-related apoptosis-inducing ligand (Apo2L/TRAIL) is a recently identified member of the TNF superfamily. Recombinant Apo2L/TRAIL is a promising immunotherapeutic agent for treating malignant diseases since this molecule preferentially induces apoptosis in a variety of tumor cells with apparently little toxicity to normal cells. However, it has also been shown that some tumor cells are resistant to this molecule. We hypothesized that resistance to Apo2L/TRAIL occurs through defects in the Apo2L/TRAIL-mediated apoptotic signaling pathway. To address this hypothesis, we developed several Apo2L/TRAIL-resistant HL60 derivatives (HL60/TR) by exposure of Apo2L/TRAIL-sensitive HL60 human leukemia cells to escalating levels of Apo2L/TRAIL, followed by subcloning. Two of these resistant clones (a moderately resistant clone-R1 and a highly resistant clone-R3) were selected for further study. Molecules in the Apo2L/TRAIL-mediated apoptotic pathway of R1 and R3 cells were analyzed by Western blot analysis, flow cytometry and gene sequencing and compared to those in parental HL60 cells. In the R1 cells, the activation of caspase-8 and -10 by Apo2L/TRAIL was significantly inhibited. However, R1 cells were still sensitive to Fas agonistic monoclonal antibody treatment, indicating that the FAS-mediated apoptosis-inducing pathway was intact. In the R3 cells, caspase-8 expression was completely lost and activation of caspase-10 in response to Apo2L/TRAIL was totally inhibited; R3 cells were therefore also resistant to FAS antibody treatment. Although the total protein level of death receptors DR4 and DR5 was equal in HL60 cells and in the Apo2L/TRAIL-resistant derivatives, the cell surface levels of DR4 were significantly decreased in both R1 and R3 cells, while the surface expression level of DR5 in these two clones was comparable to that on HL60 cells. No mutation in either the DR4 or DR5 genes was found in these cells. These results suggest that defective targeting of DR4 molecules to the cell surface occurs in these Apo2L/TRAIL resistant cells. Blocking cell surface DR4 significantly attenuated the sensitivity of parental HL60 cells to Apo2L/TRAIL, indicating that cell surface expression of DR4 plays a crucial role in regulating susceptibility of tumor cells to Apo2L/TRAIL. Taken together, our results demonstrate that malignant cells can develop resistance to Apo2L/TRAIL by several different mechanisms and multiple resistance mechanisms may develop in a single tumor cell (such as R3 cells). Understanding the basis of Apo2L/TRAIL resistance will help to predict sensitivity and to develop strategies to circumvent resistance.

CHOP Is Involved in Endoplasmic Reticulum Stress-induced Apoptosis by Enhancing DR5 Expression in Human Carcinoma Cells

It has been shown that excess stress to the endoplasmic reticulum (ER) triggers apoptosis, but the mechanisms underlying these processes remain unclear. We and others have reported previously that DR5 expression is up-regulated in thapsigargin (THG)-treated human cancer cells. Here, we provide evidence that CHOP is involved in THG up-regulation of DR5, which is a critical step for ER stress-induced apoptosis in human cancer cells. In human colon cancer HCT116 cells, knockdown of DR5 by siRNA blocked THG-induced Bax conformational change along with caspase-3 activation and cell death. Moreover, inhibition of CHOP expression attenuated DR5 up-regulation and apoptosis induced by THG, whereas ectopic expression of DR5 restored the sensitivity of CHOP siRNA-transfected cells to THG-induced apoptosis. In addition to HCT116 cells, inhibition of CHOP or DR5 induction also attenuated THG-induced cell death in other cancer cell lines including LNCaP, A2780S, and DU145, indicating that CHOP and DR5 are critical for ER stress-mediated apoptosis in human carcinoma cells. Furthermore, we identified a potential CHOP-binding site in the 5'-flanking region of the DR5 gene. Mutation of this site abrogated the enhanced reporter activity in response to THG treatment. Together, our findings suggest that CHOP regulates ER stress-induced apoptosis, at least in part, through enhancing DR5 expression in some types of human cancer cells.

P53 upregulates death receptor 4 expression through an intronic p53 binding site.

Death receptor 4 (DR4) is one of the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptors and triggers apoptosis on ligation with TRAIL or overexpression. Our previous study demonstrated that DR4 expression could be regulated in a p53-dependent fashion. In the present study, we have demonstrated that DR4 is a p53 target gene and is regulated by p53 through a functional intronic p53 binding site (p53BS) based on the following lines of evidence: (a) the p53BS in the DR4 gene is almost identical to the one found in the first intron of the DR5 gene in terms of their locations and sequences; (b) DR4 p53BS bound to p53 protein in intact cells upon p53 activation as demonstrated by a chromatin immunoprecipitation assay; (c) a luciferase reporter vector carrying the DR4 p53BS upstream of an SV40 promoter exhibited enhanced luciferase activity when transiently cotransfected with a wild-type p53 expression vector in p53-null cell lines or stimulated with DNA-damaging agents in a cell line having wild-type p53; and (d) when the DR4 p53BS, together with its own corresponding promoter region in the same orientation as it sits in its natural genomic locus, was cloned into a basic luciferase vector without a promoter element, its transcriptional activity was strikingly increased by cotransfection of a wild-type p53 expression vector or treatment with DNA-damaging agents. However, wild-type p53 or DNA-damaging agents completely lost their activity to increase transcriptional activity of a reporter construct with deleted DR4 p53BS. Thus, we conclude that p53 directly regulates the expression of the DR4 gene via the novel intronic p53BS.

Sodium butyrate sensitizes TRAIL-mediated apoptosis by induction of transcription from the DR5 gene promoter through Sp1 sites in colon cancer cells.

Sodium butyrate, a short-chain fatty acid naturally present in the human colon, is able to induce cell cycle arrest, differentiation and apoptosis in various cancer cells. Sodium butyrate is most probably related to the inhibition of deacetylases leading to hyperacetylation of chromatin components such as histones and non-histone proteins and to alterations in gene expression. In this study, we demonstrate for the first time that sodium butyrate selectively up-regulated DR5 but had no effect on the expression of the other TNF-alpha-related apoptosis-inducing ligand (TRAIL) receptor, DR4. Sodium butyrate-induced expression of DR5 involves the putative Sp1 site within the DR5 promoter region. Using a combination of the electrophoretic mobility shift assay and the luciferase reporter assay, we found that a specific Sp1 site (located at -195 bp relative to the transcription start site) is required for sodium butyrate-mediated activation of the DR5 promoter. When HCT116 cells were incubated with sodium butyrate and TRAIL, enhanced TRAIL-mediated apoptosis was observed. The enhanced apoptosis was measured by fluorescent activated cell sorting analysis, DNA fragmentation, poly (ADP-ribose) polymerase cleavage, down-regulation of XIAP and caspase activity. Taken together, the present studies suggest that sodium butyrate may be an effective sensitizer of TRAIL-induced apoptosis.

Mutation analysis of the apoptotic "death-receptors" and the adaptors TRADD and FADD/MORT-1 in osteosarcoma tumor samples and osteosarcoma cell lines.

Apoptosis is a key mechanism of the organism that regulates embryogenesis and development, maintains homeostasis of the immune system and removes potentially hazardous cells. A dysregulation of apoptosis signaling may thus disturb the balance of cell survival and cell death, leading to the development of several diseases including cancer. In order to determine whether osteosarcomas display an increased frequency of genetic alterations that affect apoptosis signaling, we analyzed the death domains of the death receptor genes CD95/Fas/Apo1, TNFR1, DR3/Apo3/WSL-1/LARD/TRAMP, DR5/TRAIL-R2/TRICK2/KILLER, DR6 and the complete coding sequences of the death receptor gene DR4/TRAIL-R1 and the genes of the adaptors TRADD and FADD/MORT-1. The investigation included 15 osteosarcoma tumor samples, 3 osteosarcoma cell lines (SAOS-2, HOS and MG63) and peripheral blood from 20 donors as controls. We were able to identify 4 different sequence variations within the DR4 gene located on exons 3, 4, 5 and 10 (death-domain). No alterations have been detected in the other genes or exons investigated. Except the sequence variant affecting exon 4, the alterations were homozygous in 15% of the tumor samples and cell lines, whereas the same alterations found in the control group were heterozygous or even not detectable. Three out of 4 alterations are located in the receptor's extracellular cysteine rich domain, which contains the ligand binding area and 1 on exon 10 coding for the death-domain. They may thus exert influence on ligand-receptor interactions and subsequent apoptosis induction. Our findings suggest that homozygous genetic alterations within the DR4 gene may be implicated in the formation of osteosarcoma.

TRAIL and Ceramide

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a clinically useful cytokine. TRAIL induces apoptosis in a wide variety of transformed cells, but does not cause toxicity to most normal cells. Recent studies show that death receptors (DR4 and DR5), decoy receptors (DcR1 and DcR2), and death inhibitors (FLIP, FAP-1, and IAP) are responsible for the differential sensitivity to TRAIL of normal and tumor cells. Several researchers have also shown that genotoxic agents, such as chemotherapeutic agents and ionizing radiation, enhance TRAIL-induced cytotoxicity by increasing DR5 gene expression or decreasing the intracellular level of FLIP, an antiapoptotic protein. Previous studies have shown that ceramide helps to regulate a cell's response to various forms of stress. Stress-induced alterations in the intracellular concentration of ceramide occur through the activation of a variety of enzymes that synthesize or catabolize ceramide. Increases in intracellular ceramide levels modulate apoptosis by acting through key proteases, phosphatases, and kinases. This review discusses the interaction between TRAIL and ceramide signaling pathways in regulating apoptotic death.

Evidence that the human death receptor 4 is regulated by activator protein 1.

Death receptor 4 (DR4; also called TRAIL-R1), a member of the tumor necrosis factor receptor superfamily, is a cell surface receptor that triggers the apoptotic machinery upon binding to its ligand tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Although several chemotherapeutic agents were reported to induce DR4 expression, the mechanism of this effect remains largely unknown. To begin to understand its regulation, we cloned a 1.8 Kb 5'-flanking region of the human DR4 gene and identified several putative binding sites for transcription factors including activator protein 1 (AP-1). Among the three putative AP-1 binding sites, the site located at -350/-344 is functionally active as evidenced by a combination of electrophoretic mobility shift and luciferase reporter assays. The AP-1 activator phorbol 12-myristate 13-acetate (TPA) enhanced the binding of this DR4 AP-1 binding site to protein(s) in a nuclear extract from TPA-treated cells, increased luciferase activity of a reporter construct containing this site and induced DR4 expression at the transcription level. These results indicate that AP-1 regulates DR4 expression via the AP-1 binding site located at -350/-344. AP-1 has been implicated in many critical cellular processes including apoptosis, and is a major target of the c-Jun NH(3)-terminal kinase signaling pathway that is activated by many anticancer drugs. Therefore, our findings may increase the understanding of the mechanisms underlying AP-1-mediated apoptosis as well as drug-induced apoptosis.

Homozygous deletion of the death receptor DR4 gene in a nasopharyngeal cancer cell line is associated with TRAIL resistance.

The family of tumor necrosis factor related apoptosis inducing ligand (TRAIL) receptors, including the pro-apoptotic DR4 and p53-regulated KILLER/DR5, as well as the decoys TRID and TRUNDD, are all located on human chromosome 8p21-22. This region of the genome is frequently altered in head and neck cancer. We previously reported that KILLER/DR5 can be mutationally inactivated in head and neck cancer. Here, we report that the FaDu nasopharyngeal cancer cell line contains an abnormal chromosome 8p21-22 region. In addition, there appears to be a homozygous deletion involving DR4 but not KILLER/DR5 in FaDu cells. The homozygous loss within the DR4 gene encompasses its death domain, which is required for apoptotic signaling. The deletion of DR4 in FaDu cells is associated with resistance to the cytotoxic effects of TRAIL. Re-introduction of wild-type DR4 leads to apoptosis and restores TRAIL sensitivity of FaDu cells. These observations suggest that the death inducing DR4 receptor gene may be a rare target for inactivation in human cancer and that DR4 loss may contribute to resistance to TRAIL therapy.

Complementation between HLA-DR4 (DRB1∗0401) and specific H2-A molecule in transgenic mice leads to collagen-induced arthritis

We generated transgenic mice with DRB1∗0401 gene with mutation in the β2 domain (aa 110 and 139) for better interaction with mCD4. The DR4 transgene was introduced into H2-A q (B10RQB3) and H2-A f (B10RFB3) to examine the role of DR4 in collagen arthritis. The HLA-DR molecules in these mice were found to be functional on the basis of their positive/negative selection of the Vβ T cell repertoire. H2-A qmice are resistant to porcine CII-induced arthritis. The RQB3/DR4 mice (H2A q/DR4) developed severe collagen induced arthritis (CIA) when immunized with Porcine type II collagen while the negative littermates were resistant. RQB3.DR4 mice were also highly susceptible to CIA induced by Human CII while negative littermates got only mild disease. However, RFB3/DR4 mice (H2A f/DR4) did not get CIA with any type II collagen. Therefore, the DR4 gene in the context of H2-A q predisposes to severe arthritis but not in the context of H2-Af. Antibodies to renatured cyanogen bromide (CB) cleaved fragments of PII in RQB3/DR4 mice and negative littermates suggest that the presence of DR4 does not result in any differences in specificity of antibody response to CB fragments. These results indicate that a specific gene complementation occurring between DR4 and H2.A q but not DR4 and H2A f promotes the induction of arthritis with PII and HII in these mice. A similar interaction may be involved between DR and DQ molecules in human RA.

Association of the HLA-DR4 gene complex with auto-antibodies in rheumatoid arthritis patients

The HLA-DR4 gene complex plays a role in the pathogenesis of rheumatoid arthritis (RA). Auto-antibodies are a prominent serum feature of RA. In this study we explored the correlation of the HLA-DR4 gene complex with rheumatoid factor, anti-RA33/36 antibody, anti-keratin antibody (AKA) and anti-perinuclear factor (APF) in RA patients. Forty-five RA patients were involved in this study. The PCR-SSP method was used to examine the DR4 gene complex. Anti-RA33/36 antibody and RF were tested by Western blot and latex agglutination test respectively. AKA and APF were tested by the indirect immunofluorescence method. The DR4 gene complex is present in 60% of our patients. RF positivity was 68.9%. DR4(+) patients had a higher RF positive rate (66.7%) than DR4(−) patients (33.3%) (P<0.05). Anti-RA33/36 antibody was positive in 37.8% patients. It was present in 33.3% DR4(+) patients and in 38.9% DR4(−) patients. There was no significant difference. AKA (1∶80) was positive in 28.9% of our patients. It was present in 33.3% DR4(+) patients and in 22.2% DR4(−) patients. No significant difference could be found. APF could be detected in 53.3% of these patients. It was positive in 51.9% DR4(+) patients and 55.5% DR4(−) patients. There was no significant difference. In addition, no association could be found between RF, anti-RA33/36 antibody, AKA and APF. Therefore, although DR4 is an important indicator for severe RA and poor prognosis, it is only associated with RF. Moreover, no correlation could be found between these auto-antibodies.

Association of the HLA-DR4 gene complex with auto-antibodies in rheumatoid arthritis patients

The HLA-DR4 gene complex plays a role in the pathogenesis of rheumatoid arthritis (RA). Auto-antibodies are a prominent serum feature of RA. In this study we explored the correlation of the HLA-DR4 gene complex with rheumatoid factor, anti-RA33/36 antibody, anti-keratin antibody (AKA) and anti-perinuclear factor (APF) in RA patients. Forty-five RA patients were involved in this study. The PCR-SSP method was used to examine the DR4 gene complex. Anti-RA33/36 antibody and RF were tested by Western blot and latex agglutination test respectively. AKA and APF were tested by the indirect immunofluorescence method. The DR4 gene complex is present in 60% of our patients. RF positivity was 68.9%. DR4(+) patients had a higher RF positive rate (66.7%) than DR4(−) patients (33.3%) (P<0.05). Anti-RA33/36 antibody was positive in 37.8% patients. It was present in 33.3% DR4(+) patients and in 38.9% DR4(−) patients. There was no significant difference. AKA (1∶80) was positive in 28.9% of our patients. It was present in 33.3% DR4(+) patients and in 22.2% DR4(−) patients. No significant difference could be found. APF could be detected in 53.3% of these patients. It was positive in 51.9% DR4(+) patients and 55.5% DR4(−) patients. There was no significant difference. In addition, no association could be found between RF, anti-RA33/36 antibody, AKA and APF. Therefore, although DR4 is an important indicator for severe RA and poor prognosis, it is only associated with RF. Moreover, no correlation could be found between these auto-antibodies.

Genomic organization and mutation analyses of the DR5/TRAIL receptor 2 gene in colorectal carcinomas

The DR5/TRAIL receptor 2 gene is a novel TNF receptor family member and induces apoptosis by overexpression of its product. DR5 is located on chromosome 8p21, where allelic deletions are often observed in advanced colorectal cancers. This evidence led us to examine whether or not mutations of the DR5 gene exist in these tumors. We determined the genomic structure of DR5, which consists of nine exons. DR5 has two alternatively spliced isoforms. All seven colorectal cancer (CRC) cell lines examined expressed the longer isoform predominantly. No somatic mutation was found in 41 CRC cases. Loss of heterozygosity of DR5 was found in nine (52.9%) of the 17 informative cases, which is similar to the previously reported frequencies observed for 8p21-22 in colorectal cancers. These findings suggest that inactivation of the DR5 gene may play only a small role, if any, in colorectal tumorigenesis.

Maternal exposure to paternal HLA does not explain the postpartum increase in rheumatoid arthritis.

The postpartum period, particularly after the first pregnancy, represents a time of increased risk for the development of rheumatoid arthritis (RA). The present study was undertaken to investigate whether this increase in risk may be due to maternal exposure to fetally inherited paternal HLA-DR antigens that were either 1) similar to their own or 2) had an increased likelihood of being one of the two specific types, HLA-DR1 and DR4, implicated in the etiology of RA. We recruited 94 families where the mother had developed RA within 12 months of a pregnancy, and HLA typed the mother, father, and relevant child of each family. Mothers were not more likely to share HLA-DR genes with their partners than would be expected, and children whose parents shared one HLA-DR gene were not more likely to inherit the shared gene from their father as opposed to the non-shared gene. Further, those children whose fathers were heterozygous for HLA-DR1 or DR4 were not more likely to inherit these genes as opposed to the non-DR1/DR4 gene. In conclusion, maternal exposure during pregnancy to either fetally inherited paternal HLA-DR1 and DR4 genes or to paternal DR genes similar to their own does not appear to contribute to postpartum maternal susceptibility of RA.

Relative abilities of distinct isotypes of human major histocompatibility complex class II molecules to bind streptococcal pyrogenic exotoxin types A and B.

The relative ability of distinct isotypes of human leukocyte antigen class II molecules to bind streptococcal pyrogenic exotoxins A and B (SPE A and SPE B, respectively) was investigated by a direct-binding assay with 125I-labeled toxin for SPE A and by a functional assay system measuring the accessory cell activity of human leukocyte antigen class II transfectants in toxin-induced T-cell activation for SPE A and SPE B. SPE A binding was observed in L cells transfected with DQw1 genes. By contrast, it was not detected in L cells transfected with DR2, DR4, DPw4 or DP(Cp63) genes. All the transfectants supported SPE-induced interleukin-2 production by human T cells except the DP transfectants for SPE B. Levels of accessory cell activity were low in the DP transfectants induced by stimulation with SPE A and in the DR and DP transfectants induced by SPE B. The results indicate that SPE A and SPE B bind well to DQ molecules, less well to DR molecules, and very weakly to DP molecules.

HLA-DR4-associated nonresponsiveness to mountain-cedar allergen

We did human lymphocyte antigen (HLA)-DR and DQ typing on 37 subjects with mountain-cedar (MC) pollinosis as defined by history and a positive skin test. Of these 37 subjects, 31 were subdivided into 18 subjects with a single positive skin test (SPST) and 13 subjects with multiple positive skin tests (MPSTs). We also typed 51 subjects without MC sensitivity or atopy as defined by history and negative skin tests to a battery of aeroallergens. We also typed 116 subjects in whom MC sensitivity had not been determined. Total IgE. MC-specific immunoglobulin E (sIgE), and MC-sIgE binding bands by immunoblot were also determined on the subjects with SPSTs and MPSTs. No significant differences were found between the subjects with SPSTs and MPSTs for HLA type, total IgE, MC sIgE, or bands bound by MC sIgE by immunoblot. There was a strong negative relationship between HLA-DR4 and subjects with MC pollinosis; chi-square, 14.857; p = 0.0096; and odds ratio, 0.139. These findings suggest that there is no difference in genetic immunoregulation between subjects with SPSTs and MPSTs but that the presence of the DR4 gene product is associated with a decreased risk of an IgE response to MC and protection from MC pollenosis.

Demonstration of the requirement for self antigen in the activation of autoreactive T cells.

An HLA-DR4-restricted T cell clone (26G11), which was reactive to autologous non-T cells without any nominal antigens, was established from an unimmunized normal subject that was DR1/4 positive. The reactivity of the clone was examined against L cells (LDR4) transfected with the particular DR4 genes obtained from the same subject. 26G11 cells proliferated slightly in response to LDR4 cells, but the proliferation was markedly augmented by the addition of cell lysate from an autologous B cell line. In addition, 26G11 cells killed LRD4 cells sensitized by preincubation with the cell lysate more efficiently than LDR4 cells without treatment. When LDR4 cells were preincubated with cell lysate from allogenic B cell lines, effective killing of the target cells by clone 26G11 was also observed. These data strongly suggest that this autoreactive T cell clone (26G11) recognizes endogenous antigen in the context of the DR4 molecule. This directly demonstrates the requirement for self antigen in the activation of human autoreactive T cells from a normal subject.

Susceptibility to autoimmune chronic active hepatitis: Human leukocyte antigens DR4 and A1-B8-DR3 are independent risk factors

After nearly 18 years of research, the association between human leukocyte antigens A1-B8-DR3 and autoimmune chronic active hepatitis still provokes debate. The principal reasons for this are disease heterogeneity and racial variation in the distribution of human leukocyte antigens between populations. The aim of the present study was to reexamine the relationship between these antigens and autoimmune chronic active hepatitis in a well-characterized series of patients. Ninety-six outpatients with autoimmune chronic active hepatitis and an additional 14 referred for liver transplantation with end-stage autoimmune chronic active hepatitis were studied. Human leukocyte antigen frequencies were compared with those of 100 racially and geographically matched controls. The A1-B8-DR3 haplotype was present in 38% of patients compared with 11% of controls (chi 2 = 20.6, p less than 0.0005). When all the DR3-positive patients were eliminated, there was a striking secondary association with DR4; 35 (80%) of 44 remaining patients were DR4 positive compared with 31 (39%) of 79 DR3-negative controls (Fisher's exact probability test p = 0.000031, pc = 0.0013). In addition patients with A1-B8-DR3 are seen at a significantly younger age than those without (39.75 yr vs. 48.21 yr, p less than 0.025), relapse more frequently (52% of patients with A1-B8-DR3 relapsed on one or more occasions compared with 34% of patients without this haplotype) and are more frequently referred for liver transplantation. These data indicate for the first time that two genes within the major histocompatibility complex closely linked to the DR3 and DR4 genes independently confer susceptibility to autoimmune chronic active hepatitis.

Susceptibility to autoimmune chronic active hepatitis: Human leukocyte antigens DR4 and A1-B8-DR3 are independent risk factors

After nearly 18 years of research, the association between human leukocyte antigens A1-B8-DR3 and autoimmune chronic active hepatitis still provokes debate. The principal reasons for this are disease heterogeneity and racial variation in the distribution of human leukocyte antigens between populations. The aim of the present study was to reexamine the relationship between these antigens and autoimmune chronic active hepatitis in a well-characterized series of patients. Ninety-six outpatients with autoimmune chronic active hepatitis and an additional 14 referred for liver transplantation with end-stage autoimmune chronic active hepatitis were studied. Human leukocyte antigen frequencies were compared with those of 100 racially and geographically matched controls. The A1-B8-DR3 haplotype was present in 38% of patients compared with 11% of controls (x2 = 20.6, p < 0.0005). When all the DR3-positive patients were eliminated, there was a striking secondary association with DR4; 35 (80%) of 44 remaining patients were DR4 positive compared with 31 (39%) of 79 DR3-negative controls (Fisher's exact probability test p = 0.000031, pc = 0.0013). In addition patients with A1-B8-DR3 are seen at a significantly younger age than those without (39.75 yr vs. 48.21 yr, p < 0.025), relapse more frequently (52% of patients with A1-B8-DR3 relapsed on one or more occasions compared with 34% of patients without this haplotype) and are more frequently referred for liver transplantation. These data indicate for the first time that two genes within the major histocompatibility complex closely linked to the DR3 and DR4 genes independently confer susceptibility to autoimmune chronic active hepatitis. (HEPATOLOGY 1991;13:701–706.)

B27-bearing HLA haplotypes in rheumatoid arthritis: Characterization in finnish patients

The frequency of human leukocyte antigen (HLA)-B27 has been found to be increased in rheumatoid arthritis (RA) in Finland and marginally also in some other populations. In the present study HLA-B27-bearing haplotypes in RA patients were found to carry DR1 and DR4 genes more often than do B27 haplotypes in control population. B27;DR4,Dw14;DQw7 was a typical B27-DR4 haplotype whereas DR4 in the majority of other haplotypes occurs with Dw4 and DQw8 genes. The result indicates that the B27 association with RA is not independent of DR1 and DR4, but whether the B27;DR4;DQw7 haplotype subjects a person to a higher disease risk than do other DR4 haplotypes, or is associated with a more severe course of the disease, remains to be investigated.

HLA extended haplotypes in childhood and adult onset HLA—DR4‐associated arthropathies

Alpha HLA-DR4 extended haplotypes have been established by family studies in children and adults with chronic arthritis, the children having polyarticular juvenile rheumatoid arthritis and the adults rheumatoid arthritis. These diseases are probably the same disorder presenting at different ages. The results demonstrate age-related differences in the frequency of HLA-DR4 extended haplotypes between the two groups of patients. The childhood onset was associated with the presence of the HLA-B44, SC30, DR4 extended haplotype, whereas the adult form was more strongly associated with the HLA-Bw62, SC33, DR4 haplotype. These results suggest that differences in the age at onset are influenced by the MHC in addition to the presence of the HLA DR4 gene itself.