Lawrence J. Abraham

The −308 tumor necrosis factor-α promoter polymorphism effects transcription

Since the tumor necrosis factor alpha (TNF-α) gene was found to be located in the central major histocompatibility complex (MHC) there has been much speculation concerning a genetic association between particular TNF alleles and disease susceptibility. A relationship between the MHC haplotype Al, B8, DR3, TNF-α expression levels and susceptibility to autoimmune disease has been suggested by several groups. The identification of the −308 polymorphism and its association with the HLA Al, B8, DR3 haplotype have led to speculation that the polymorphism may play a role in the altered expression of TNF-α. We have demonstrated that the region (−323 to −285) encompassing −308 in the TNF2 allele binds nuclear factors differently to the same region in the promoter of the more common TNF1 allele. The GA −308 polymorphism affected the affinity of factor binding and resulted in a factor binding to TNF2 but not TNF1. The observed differential binding was shown to be functional, with the 38 by region from TNF2 causing a two-fold greater activity of a heterologous promoter over that due to the same region in TNFI. To further substantiate the functional consequences of the TNF-α −308 polymorphism, we analysed both allelic forms of the TNF-α promoter region (−993 to +110) in a transient transfection assay, using luciferase as a reporter gene. The results showed that when present with the 3′UTR the −308A allelic form gave a two-fold greater level of transcription than the −308G form in PMA-stimulated Jurkat and U937 cells. This suggests that the −308 GA polymorphism may play a role in the altered TNF-α gene expression observed in individuals with the HLA Al, B8, DR3 haplotype.

Impact of the -308 TNF promoter polymorphism on the transcriptional regulation of the TNF gene: relevance to disease.

A biallelic G (TNF1 allele) to A (TNF2 allele) polymorphism 308 nucleotides upstream from the transcription initiation site in the tumor necrosis factor (TNF) promoter is associated with elevated TNF levels and disease susceptibilities observed in human subjects. The TNF2 allele is strongly associated with the high‐TNF‐producing autoimmune MHC haplotype HLA‐A1, B8, DR3, with elevated serum TNF levels and a more severe outcome in infectious diseases, such as cerebral malaria. A number of groups have set out to determine whether the ‐308 polymorphism could affect transcription factor binding and hence influence TNF transcription and expression levels. Although some studies have failed to show any functional difference between the two allelic forms, others have shown that the ‐308 polymorphism effected transcription factor binding to the region encompassing ‐308, with the region in the TNF2 allele showing altered binding characteristics. The ‐308 polymorphism also has been found by some groups to be functionally significant in reporter gene assays in Raji B cells, Jurkat T cells, and U937 pre‐monocytic cells. Up to fivefold differences can be measured between TNF1 and TNF2 allelic constructs when the TNF 3′UTR is present, indicating a role in the expression of the polymorphism. Although controversial, the majority of the data support a direct role for the TNF2 ‐308 allele in the elevated TNF levels observed in TNF2 homozygotes and HLA‐A1, B8, DR3 individuals. Elevated TNF levels due to the ‐308 polymorphism may alter the immune response such that it confers susceptibility to certain autoimmune and infectious diseases. J. Leukoc. Biol. 66: 562–566; 1999.

Ancestral haplotypes: conserved population MHC haplotypes

We describe here a number of Caucasoid MHC haplotypes that extend from HLA-B to DR and that have been conserved en bloc. These haplotypes and recombinants between any two of them account for 73% of unselected haplotypes in our Caucasoid population. The existence of ancestral haplotypes implies conservation of large chromosomal segments. Irrespective of the mechanisms involved in preservation of ancestral haplotypes, it is clear that these haplotypes carry several MHC genes, other than HLA, which may be relevant to antigen presentation, autoimmune responses, and transplantation rejection. In light of the existence of ancestral haplotypes, it is critical to evaluate MHC associations with disease and transplantation outcome in terms of associations with ancestral haplotypes rather than individual alleles.

Polymorphisms in cytokine genes define subpopulations of HIV-1 patients who experienced immune restoration diseases

Objective: To further elucidate the immunopathogenesis of immune restoration diseases (IRD) in HIV patients responding to antiretroviral therapy and determine whether IRD associated with different opportunistic pathogens involve distinct immunopathological mechanisms. Design: DNA samples from patients with a range of IRD were typed for polymorphic loci in genes encoding immune-mediators. Methods: PCR–restriction fragment length polymorphism assays were used to type loci in the IL1A, IL1B, IL6, TNFA and IL12B genes. Alleles of a microsatellite in the CD30 promoter were determined by capillary electrophoresis. Results: Only 8% of patients with IRD associated with a herpesvirus infection carried IL12B-3′UTR*2, compared with 42–54% of patients with other or no IRD. Patients with IRD arising from mycobacterial infection rarely carried IL6-174*C (36% versus 61–71%) and never carried TNFA-308*2 (0% versus 23–52%). TNFA-308*2 was carried by 52% of patients who experienced IRD associated with a herpesvirus infection, as several patients with exacerbations of cytomegalovirus retinitis carried this as part of a HLA-A2,B44 haplotype. Polymorphisms in IL1A, IL1B and CD30 showed no distinct patterns. Conclusions: Distinct cytokine-mediated mechanisms contribute to IRD initiated by herpesvirus and mycobacterial infections.

Oval cell‐mediated liver regeneration: Role of cytokines and growth factors

Abstract   In experimental models, which induce liver damage and simultaneously block hepatocyte proliferation, the recruitment of a hepatic progenitor cell population comprised of oval cells is invariably observed. There is a substantial body of evidence to suggest that oval cells are involved in liver regeneration, as they differentiate into hepatocytes and biliary cells. Recently, bone marrow cells were shown to be a source of a stem cells with the capacity to repopulate the liver. Presently, the relationship between bone marrow cells and oval cells is unclear. Investigations will be greatly assisted by the availability of in vitro models based on a knowledge of cytokines that affect oval cells. While the cytokines, which regulate the different hematopoietic lineages, are well characterized, there is relatively little information regarding those that influence oval cells. This review outlines recent developments in the field of oval cell research and focuses on cytokines and growth factors that have been implicated in regulating oval cell proliferation and differentiation.

Polymorphic MHC ancestral haplotypes affect the activity of tumour necrosis factor‐alpha

It remains unclear which MHC loci are involved in susceptibility to autoimmune diseases and immune deficiencies. We have chosen to evaluate whether different alleles of tumour necrosis factor‐alpha (TNF‐α) are important, as TNF has been implicated in the etiology of many immunological disorders. We have shown previously that a restriction fragment length polymorphism in the TNF region correlates with MHC ancestral haplotypes. We therefore examined the effect of ancestral haplotype on the activity of TNF‐α in culture supernatants of lymphoblastoid cell lines. The results demonstrate that TNF‐α activity in supernatants of 8.1 (A1, B8, DR3) cell lines was higher than that present in the supernatants from cells homozygous for eight different MHC ancestral haplotypes, and indicate that polymorphisms in TNF‐α, or in other MHC genes that regulate TNF, may be responsible for the 8.1 phenotype.

A new polymorphic and multicopy MHC gene family related to nonmammalian class I

We have used genomic analysis to characterize a region of the central major histocompatibility complex (MHC) spanning ∼ 300 kilobases (kb) betweenTNF andHLA-B. This region has been suggested to carry genetic factors relevant to the development of autoimmune diseases such as myasthenia gravis (MG) and insulin dependent diabetes mellitus (IDDM). Genomic sequence was analyzed for coding potential, using two neural network programs, GRAIL and GeneParser. A genomic probe, JAB, containing putative coding sequences (PERB11) located 60 kb centromeric ofHLA-B, was used for northern analysis of human tissues. Multiple transcripts were detected. Southern analysis of genomic DNA and overlapping YAC clones, covering the region fromBAT1 toHLA-F, indicated that there are at least five copies of PERB11, four of which are located within this region of the MHC. The partial cDNA sequence ofPERB11 was obtained from poly-A RNA derived from skeletal muscle. The putative amino acid sequence ofPERB11 shares ∼ 30%o identity to MHC class I molecules from various species, including reptiles, chickens, and frogs, as well as to other MHC class I-like molecules, such as the IgG FeR of the mouse and rat and the human Zn-α2-glycoprotein. From direct comparison of amino acid sequences, it is concluded thatPERB11 is a distinct molecule more closely related to nonmammalian than known mammalian MHC class I molecules. Genomic sequence analysis ofPERB11 from five MHC ancestral haplotypes (AH) indicated that the gene is polymorphic at both DNA and protein level. The results suggest thet we have identified a novel polymorphic gene family with multiple copies within the MHC.

Glucocorticoid modulation of human monocyte/macrophage function: Control of TNF-alpha secretion

Abstract. Glucocorticoids suppress many functions in activated monocyte/macrophages, including the release of TNF-α. This is likely to contribute to the efficacy of glucocorticoids in some inflammatory diseases, such as rheumatoid arthritis, where TNF-α contributes to pathogenesis. Glucocorticoids suppress the activity of reporters which include TNF-α promoter regions and modify the activity of NF-κB family transcription factors in activated human monocytic cell lines, suggesting effects of glucocorticoids on TNF-α gene transcription. In addition, glucocorticoids have been reported to antagonise the enhanced translational efficiency of TNF-α mRNA which occurs at least after stimulation of murine monocytic cells. It is likely, therefore, that glucocorticoids act at several points in stimulated monocyte/macrophages to reduce TNF-α secretion. Understanding glucocorticoid control of TNF-α secretion may explain some of the variability in response to GC in inflammatory diseases and may reveal means of inducing glucocorticoid-like anti-inflammatory effects in monocyte/macrophages without exposing other tissues to the adverse effects of glucocorticoids.

Ancestral haplotypes reveal the role of the central MHC in the immunogenetics of IDDM

The major histocompatibility complex (MHC) contains multiple and diverse genes which may be relevant to the induction adn regulation of autoimmune responses in insulin dependent diabetes mellitus (IDDM). In addition to HLA class I and II, the possible candidates include TNF, C4, and several other poorly defined polymorphic genes in the central MHC region. This study describes two approaches which take advantage of the fact that the relevant genes are carried by highly conserved ancestral haplotypes such as 8.1 (HLA-B8, TNFS, C4AQO, C4B1, DR3, DQ2). First, three “diabetogenic” haplotypes (two Caucasoid and one Mongoloid) have been compared and it has been shown that all three share a rare allele of BAT3 as well as sharing DR3, DQ2. In 43 sequential patients with IDDM the cross product ration for BAT3S was 4.8 (p<0.01) and 6.9 for HLA-B8 plus BAT3S (p<0.001). Second, partial or recombinant ancestral haplotypes with either HLA class I (HLA-B8) or II (HLA-DR3, DQ2) alleles were identified. Third, using haplotypic polymorphisms such as the one in BAT3, we have shown that all the patients carrying recombinants of the 8.1 ancestral haplotype share the central region adjacent to HLA-B. These findings suggest that both HLA and non-HLA genes are involved in conferring susceptibility to IDDM, and that the region between HLA-B and BAT3 contains some of the relevant genes. By contrast, similar approaches suggest that protective genes map to the HLA class II region.

JunB Induced by Constitutive CD30–Extracellular Signal-Regulated Kinase 1/2 Mitogen-Activated Protein Kinase Signaling Activates the CD30 Promoter in Anaplastic Large Cell Lymphoma and Reed-Sternberg Cells of Hodgkin Lymphoma

High expression of CD30 and JunB is characteristic of tumor cells in anaplastic large cell lymphoma (ALCL) and Hodgkin lymphoma (HL). Possible interactions of CD30 and JunB were examined in this study. We found that the CD30 promoter in tumor cells of both nucleophosmin (NPM)-anaplastic lymphoma kinase (ALK)-positive and NPM-ALK-negative ALCL and HL is regulated by a constitutively active CD30-extracellular signal-regulated kinase (ERK) 1/2 mitogen-activated protein kinase (MAPK). Phosphorylation of ERK1/2 MAPK was confirmed in nuclei of tumor cells in both ALCL and HL. CD30-ERK1/2 MAPK signals induce JunB expression, which maintains high activity of the CD30 promoter. JunB induction seems to be largely independent of nuclear factor kappaB in ALCL and HL. These results show a common mechanism of CD30 overexpression in ALCL and HL, although the outcome of CD30 signaling differs between NPM-ALK-positive ALCL and NPM-ALK-negative ALCL, cutaneous ALCL, and HL as we recently reported.