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T h e n e w e ng l a nd j o u r na l o f m e dic i n e

n engl j med 358;9 www.nejm.org february 28, 2008956

Campaign: international guidelines for management of severe sepsis and septic shock: 2008. Crit Care Med 2008;36:296-327.

Beale RJ, Hollenberg SM, Vincent JL, Parrillo JE. Vasopressor and inotropic support in septic shock: an evidence-based review. Crit Care Med 2004;32:Suppl:S455-S465.

Rivers E, Nguyen B, Havstad S, et al. Early goal-directed therapy in the treatment of severe sepsis and septic shock. N Engl J Med 2001;345:1368-77.

Trzeciak S, Dellinger RP, Abate NL, et al. Translating re-search to clinical practice: a 1-year experience with implement-ing early goal-directed therapy for septic shock in the emergency department. Chest 2006;129:225-32.

Kumar A, Roberts D, Wood KE, et al. Duration of hypoten-sion before initiation of effective antimicrobial therapy is the critical determinant of survival in human septic shock. Crit Care Med 2006;34:1589-96.

Parrillo JE. Approach to the patient with shock. In: Goldman

6.

7.

8.

9.

10.

L, Ausiello D, eds. Cecil texbook of medicine. 23rd ed. Vol. 1. Philadelphia: Saunders-Elsevier, 2008:742-50.

Hayes MA, Timmins AC, Yau EHS, Palazzo M, Hinds CJ, Watson D. Elevation of systemic oxygen delivery in the treatment of critically ill patients. N Engl J Med 1994;330:1717-22.

Landry DW, Oliver JA. The pathogenesis of vasodilatory shock. N Engl J Med 2001;345:588-95.

Dünser MW, Mayr AJ, Ulmer H, et al. Arginine vasopressin in advanced vasodilatory shock: a prospective, randomized, con-trolled study. Circulation 2003;107:2313-9.

Malay MB, Ashton RC Jr, Landry DW, Townsend RN. Low-dose vasopressin in the treatment of vasodilatory septic shock. J Trauma 1999;47:699-705.

Russell JA, Walley KR, Singer J, et al. Vasopressin versus norepinephrine infusion in patients with septic shock. N Engl J Med 2008;358:877-87.Copyright © 2008 Massachusetts Medical Society.

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Collaboration, Genetic Associations, and Lupus ErythematosusMary K. Crow, M.D.

Systemic lupus erythematosus (SLE), a disease that preferentially targets women during the re-productive years, is considered by many clinicians and investigators to be the prototypic autoimmune disease. Among clinicians, this status is based on the characteristic involvement of multiple organ systems — most notably, skin, kidneys, joints, central nervous system, and cardiovascular sys-tem — with the deposition of immune complexes and complement, inflammation, and vascular dam-age noted by pathologists. From the perspective of the immunologist, SLE is a model disease that has provided important insights into immune-system function. As is characteristic of most complex dis-eases, genetic and environmental factors determine the development of SLE and what its clinical man-ifestations will be.

Recent technological advances have allowed rapid and increasingly cost-efficient analysis of single-nucleotide polymorphisms (SNPs) in pa-tients with complex diseases and appropriate con-trol subjects. This week, important new data from two complementary genomewide association stud-ies of patients with SLE,1,2 from a third genome-wide study that focused on nonsynonymous DNA variations,3 and an analysis of an attractive can-didate gene4 are published in the Journal and in Nature Genetics. Results from these ambitious proj-ects involving international collaborations expand a growing compendium of genetic data that im-plicate many components of the immune system in the pathogenesis of SLE (Table 1).

Recognition of the essential role of innate

immune-system activation in SLE and other im-mune-mediated diseases has followed the char-acterization of toll-like receptors and their envi-ronmental and endogenous stimuli. Production of type I interferon in patients with SLE is now recognized as a central pathogenic mechanism,5 and increased serum interferon activity is a her-itable trait in families with a history of lupus (Fig. 1).6 Analysis of genes encoding components of the interferon pathway has led to extensive support for an association of polymorphic vari-ants of interferon regulatory factor 5 (IRF5) with SLE.7 The IRF5 association is replicated in both genomewide association studies reported this week,1,2 although a functional link between the IRF5 risk haplotype and increased production of type I interferon has yet to be made.

The central contribution of the adaptive im-mune response to SLE is represented by charac-teristic autoantibodies specific for nucleic-acid–containing particles (Fig. 1). The HLA locus that generates the strongest statistical association with SLE has been associated with the produc-tion of particular autoantibodies,8 suggesting that MHC class II molecules promote the expansion of autoantigen-specific T cells and the produc-tion of T-cell–dependent autoantibodies. More-over, variations in other lupus-associated genes encode proteins expressed in T and B cells that are associated with altered activation or function of those cells. Protein tyrosine phosphatase, non-receptor type 22 (PTPN22), for example, encodes a cytoplasmic lymphoid phosphatase expressed

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in hematopoietic cells, mediates interaction with Csk tyrosine kinase, and inhibits antigen-induced activation of T cells. Perhaps surprisingly, the lu-pus-associated allele of PTPN22 encodes a more active phosphatase and is associated with de-creased lymphocyte activation.9,10 Signal trans-ducer and activator of transcription 4 (STAT4) en-codes an important signaling molecule that regulates immune function, possibly through its effect on cytokine production by T cells and nat-ural killer cells.11 Both of the new genomewide association studies confirm associations of HLA and STAT4 variants with SLE (although the study that originally implicated STAT4 in lupus11 and one of the newly published genomewide studies1 share some of the same patients), and the study by the International Consortium for Systemic Lupus Erythematosus Genetics (SLEGEN)2 also confirms the role of PTPN22.

The association between lupus and the B-cell–specific tyrosine kinase gene (BLK), described in this issue of the Journal by Hom et al.,1 is novel. BLK protein is involved in the adaptive immune response and is a member of the Src kinase fam-ily (along with Fyn, Lck, and Lyn). Ligation of the B-cell surface immunoglobulin receptor (BCR) triggers an interaction between BLK and the Ig-α and Ig-β components of the BCR complex, phos-phorylation of BLK, and activation of its kinase

function.12 BLK associates with the tyrosine kinase Syk and can phosphorylate inhibitory Fc receptors on B cells, indicating that BLK may mediate both positive and negative regulatory effects. Expres-sion of an active BLK protein in the mouse pro-motes B-cell maturation that mimics responses typically generated by pre-BCR,13 suggesting that altered BLK expression or function in SLE might affect the development of the B-cell repertoire as well as mature B-cell function. Gene-expression studies performed by Hom et al. on cell lines transformed by Epstein–Barr virus and bearing the risk allele showed decreased BLK expression, but investigation of primary cells from patients with SLE and control subjects will be required to develop hypotheses about function on the basis of the genetic data.

Additional new information from a genome-wide association study of nonsynonymous SNPs in Swedish patients with SLE implicates another B-cell molecule, the B-cell scaffold protein with ankyrin repeats 1 (BANK1).3 BANK1 is an adapter protein that links the activation of Src family tyrosine kinases by B-cell–receptor ligation to calcium-channel mobilization.14 Mice that are de-ficient in BANK1 have shown spontaneous for-mation of germinal centers and augmented pro-liferative responses to CD40 ligation.15 The new data associating BLK and BANK1 variants with

Table 1. New and Confirmed Genetic Variants Conferring a Significant Risk of Systemic Lupus Erythematosus in Two Genomewide Association Studies.*

Gene Genome Location Proposed Function

HLA† 6p21.33 Presentation of antigen

HLA‡ 6p21.32 Presentation of antigen

ITGAM‡ 16p11.2 Adhesion of leukocytes to endothelial cells

IRF5‡ 7q32.1 Production of interferon-α

KIAA1542† 11p15.5 Linkage disequilibrium with IRF7; production of type I interferon

PXK† 3p14.3 Unknown effect of serine–threonine kinase

PTPN22† 1p13 Inhibition of lymphocyte activation

FCGR2A† 1q23 Clearance of immune complexes

STAT4‡ 2q32 Modulation of the production of cytokines in T cells and natural killer cells; activation of response of macrophages to interferon-α

BLK§ 8p23.1 Activation of B cells

* Data are from Hom et al.1 and from the International Consortium for Systemic Lupus Erythematosus Genetics (SLEGEN) study.2

† This variant meets the authors’ criteria for association with systemic lupus erythematosus only in the SLEGEN study.‡ This variant meets the authors’ criteria in both Hom et al. and the SLEGEN study.§ This variant meets the authors’ criteria only in Hom et al., although the SLEGEN study provides suggestive evidence

of an association at this locus.





SLE draw renewed attention to the molecular path-ways that mediate B-cell responses to antigen and T-cell help.

The effector mechanisms that are stimulated by antibodies and cytokines produced by a dys-regulated adaptive immune response contribute to inflammation and tissue damage in patients with SLE. Deficiencies of complement compo-nents that have an effect on the solubility and clearance of immune complexes and cellular de-bris are well-documented genetic contributors to lupus. Polymorphisms in several of the Fc re-ceptors for immunoglobulin have been associated with SLE,16 and the genomewide study by SLEGEN confirms a significant association between the Fc receptor for IgG (FCGR2A) and SLE.

Perhaps the strongest association uncovered by the new genetic analyses is that between disease and ITGAM, the gene encoding integrin alpha M (also known as CD11b, Mac-1, and complement receptor type 3). Additional ligands include fi-brinogen, platelet glycoprotein 1bα, lipoprotein(a), and intercellular adhesion molecules 1 and 2 (ICAM-1 and ICAM-2).17,18 Although the specific SNPs in ITGAM that are most significantly asso-ciated with SLE in three of the new studies1,2,4 are distinct, the authors of each study conclude that genetic variants could confer changes in amino acids that have an effect on binding, function, or both. Two of the studies (by SLEGEN and by Nath et al.4) provide the strongest support for an asso-ciation between a nonsynonymous SNP in ITGAM and SLE. These two studies shared one third of 9073 samples from case subjects and control sub-jects that were studied, although a combined analysis of the 7380 independent samples gen-erated a maximum combined P = 2.02×10−26 and an odds ratio of 1.65 for the association between the T allele of rs9888739 and lupus.2 Nath et al. then designated rs1143679 as a candidate causal SNP in ITGAM in patients with SLE who are of European or African descent. This variant en-codes an amino-acid change from arginine to histidine at position 77, an alteration that may modify the conformation of the protein’s α1 do-main, the region responsible for binding ICAM-1. (Complement C3 fragment iC3b binds to a dis-tinct site.)

In view of the numerous ligands that can pair with this integrin, several hypotheses can be enter-

Figure 1 (facing page). A Model of the Pathogenesis of Systemic Lupus Erythematosus (SLE) That Impli-cates the Products of Disease-Associated Polymor-phic Genes.

Candidate environmental triggers of SLE include ultra-violet light, demethylating drugs, and infectious or endogenous viruses or viral-like elements. These stim-uli induce apoptosis or generate stimulatory DNA or RNA that activates the innate immune response through pathways that are either dependent or inde-pendent of toll-like receptors, leading to secretion of type I interferon. Pathogenic variants of interferon reg-ulatory factor 5 (IRF5) and possibly of IRF7 contribute to augmented production of interferon-α by plasma-cytoid dendritic cells and an increased level of antigen presentation by myeloid dendritic cells. Impaired func-tion of molecular components of DNA checkpoint pathways, such as 3′ repair exonuclease 1 (TREX1), also generates stimulatory DNA that induces produc-tion of interferon-α. Impaired clearance of apoptotic or necrotic debris, as might occur with rare deficien-cies of complement components, can provide suffi-cient self-antigen for effective presentation to T cells. Allelic products of the HLA locus include MHC class II molecules that preferentially present disease-associat-ed self-antigens, perhaps released from apoptotic cells, to self-reactive T cells. Activation of T cells in the course of an adaptive immune response to self-anti-gens can be modified by regulators of intracellular sig-naling pathways. PTPN22, which encodes a lymphoid phosphatase, associates with CBL, CSK, and GRB2, modulating activation of T and B cells. Altered expres-sion or function of STAT4 (signal transducer and acti-vator of transcription 4) in antigen-presenting cells, T cells, or natural killer (NK) cells modifies the profile of cytokines generated, promoting interferon-γ pro-duction in response to interferon-α. T-cell–dependent activation of B cells and autoantibody production are amplified by altered expression or function of BLK (B-cell–specific tyrosine kinase) and BANK1 (B-cell scaffold protein with ankyrin repeats 1). Once autoan-tibodies have been generated, immune complexes containing nucleic acids form, stimulate toll-like recep-tors, and amplify production of interferon-α. Patho-genic variants of the Fc receptor for IgG (FCGR2A) may not adequately clear the immune complexes. The complexes accumulate in target tissues, including skin and blood vessels, which incites diffuse vasculopathy. Pathogenic ITGAM variants that alter binding to ICAM-1 (intercellular adhesion molecule 1) increase the adherence of leukocytes to endothelial cells acti-vated by antibodies or cytokines, which promotes vas-cular disease. Given the prominent vasculopathy asso-ciated with mutations in TREX1 in some patients, impaired DNA degradation and chronic DNA check-point activation preferentially occur in endothelial cells and focus immune-mediated damage on the vascula-ture. PMN denotes polymorphonuclear cell.



editorials


tained to explain the association between ITGAM and SLE. Impaired clearance of immune com-plexes would be consistent with the contribution of excess immune complexes to inflammation and tissue damage in SLE. But if the predictions of Nath et al. regarding the effect of the amino acid 77 polymorphism on the ICAM-1–binding

site are supported experimentally, attention is drawn to integrin-mediated interactions between leukocytes and endothelial cells and their role in the vasculopathy and vasculitis of SLE. Auto-antibodies can trigger endothelial-cell expression of ICAM-1 and neutrophil expression of αM-β2 integrin, but antibody-independent mechanisms





of vascular insult in SLE have been proposed by Buyon et al.19 and Belmont and Abramson20 and involve the same adhesive interactions.

The identification of ITGAM as a lupus-asso-ciated gene should rekindle interest in and in-vestigation of the mechanisms underlying many characteristic clinical and pathologic features of SLE — including “onionskinning” of splenic ar-terioles, retinopathy, livedo reticularis, the wire-loop lesions of glomerular capillaries, and pre-mature atherosclerosis (the latter being one of the most important causes of morbidity and mor-tality associated with lupus). Recent studies21,22 of rare mutations in the 3′ repair exonuclease 1 (TREX1) gene, encoding a DNase, in association with lupus and retinal vasculopathy, provide an additional rationale for the study of mechanisms of vascular disease in SLE.

All together, the new data highlight the ex-tensive variability in genes encoding mediators of innate and adaptive immune responses, includ-ing components of the signaling pathways that regulate lymphocyte activation and the cell-surface receptors that generate tissue responses. The ge-netic diversity that is described in these and other recent studies can be viewed as essential for main-taining adequate host defense against infectious microbes at the level of the aggregate human population. When the combination of variations favors immune-system activation, inflammation, and vascular damage, SLE can result. Fruitful areas for further study are identified by the re-sults of Hom et al. and SLEGEN and include the B-cell-receptor–signaling pathway and the mech-anisms of adhesion of inflammatory cells to the vasculature. The documentation of genetic as-sociations is only the first step in defining how the implicated molecular pathways contribute to disease. Ultimately, the goal should be to iden-tify therapies based on full knowledge of the molecular pathways relevant to all patients with lupus, regardless of their ancestral origin (three of the current studies1-3 were restricted to patients of European descent).

The new studies also highlight the value of structured international collaborations that make use of and recognize diverse talents and efforts. These studies, which involved investigators from academic centers in the United States and Europe, have been supported by government agencies, research foundations, and industry. Such collab-orative approaches will be needed for future studies of SLE genetics that are focused on the

patients with the most severe disease: those of African, Hispanic, and Asian descent.

Dr. Crow reports having equity interest in XDx, being an in-ventor on an application for a patent on an assay for type I inter-feron, and serving on an advisory board for the Alliance for Lupus Research. No other potential conflict of interest relevant to this article was reported.

This article (10.1056/NEJMe0800096) was published at www.nejm.org on January 20, 2008.

From the Mary Kirkland Center for Lupus Research, Hospital for Special Surgery, New York.

Hom G, Graham RR, Modrek B, et al. Association of sys-temic lupus erythematosus with C8orf13–BLK and ITGAM–ITGAX. N Engl J Med 2008;358:900-9.

International Consortium for Systemic Lupus Erythemato-sus Genetics, Harley JB, Alarcon-Riquelme ME, et al. A genome-wide association scan in women with systemic lupus erythema-tosus identifies risk variants in ITGAM, PXK, KIAA1542 and other loci and confirms multiple loci contributing to disease susceptibility. Nat Genet (in press).

Kozyrev SV, Abelson A-K, Wojcik J, et al. Functional variants in the B cell gene BANK1 are associated with systemic lupus erythematosus. Nat Genet (in press).

Nath SK, Han S, Kim-Howard X, et al. A non-synonymous functional variant in integrin-α-M (ITGAM) is associated with systemic lupus erythematosus. Nat Genet (in press).

Rönnblom L, Eloranta ML, Alm GV. The type I interferon system in systemic lupus erythematosus. Arthritis Rheum 2006; 54:408-20.

Niewold TB, Hua J, Lehman TJ, Harley JB, Crow MK. High serum IFN-alpha activity is a heritable risk factor for systemic lupus erythematosus. Genes Immun 2007;8:492-502.

Sigurdsson S, Göring HH, Kristjansdottir G, et al. Compre-hensive evaluation of the genetic variants of interferon regula-tory factor 5 reveals a novel 5bp length polymorphism as strong risk factor for systemic lupus erythematosus. Hum Mol Genet (in press).

Graham RR, Ortmann W, Rodine P, et al. Specific combina-tions of HLA-DR2 and DR3 class II haplotypes contribute graded risk for disease susceptibility and autoantibodies in human SLE. Eur J Hum Genet 2007;15:823-30.

Vang T, Congia M, Macis MD, et al. Autoimmune-associated lymphoid tyrosine phosphatase is a gain-of-function variant. Nat Genet 2005;37:1317-9.

Rieck M, Arechiga A, Onengut-Gumuscu S, Greenbaum C, Concannon P, Buckner JH. Genetic variation in PTPN22 corre-sponds to altered function of T and B lymphocytes. J Immunol 2007;179:4704-10.

Remmers EF, Plenge RM, Lee AT, et al. STAT4 and the risk of rheumatoid arthritis and systemic lupus erythematosus. N Engl J Med 2007;357:977-86.

Aoki Y, Kim YT, Stillwell R, Kim TJ, Pillai S. The SH2 do-mains of Src family kinases associate with Syk. J Biol Chem 1995;270:15658-63.

Tretter T, Ross AE, Dordai DI, Desiderio S. Mimicry of pre-B cell receptor signaling by activation of the tyrosine kinase Blk. J Exp Med 2003;198:1863-73.

Yokoyama K, Su Ih IH, Tezuka T, et al. BANK regulates BCR-induced calcium mobilization by promoting tyrosine phophory-lation of IP(3) receptor. EMBO J 2002;21:83-92.

Aiba Y, Yamazaki T, Okada T, et al. BANK negatively regu-lates Akt activation and subsequent B cell responses. Immunity 2006;24:259-68.

Salmon JE, Millard S, Schacter LA, et al. Fc gamma RIIA alleles are heritable risk factors for lupus nephritis in African Americans. J Clin Invest 1996;97:1348-54.

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Wang Y, Sakuma M, Chen Z, et al. Leukocyte engagement of platelet glycoprotein Ibalpha via the intergrin Mac-1 is critical for the biological response to vascular injury. Circulation 2005;112:2993-3000.

Sotiriou SN, Orlova VV, Al-Fakhri N, et al. Lipoprotein(a) in atherosclerotic plaques recruits inflammatory cells through in-teraction with Mac-1 integrin. FASEB J 2006;20:559-61.

Buyon JP, Shadick N, Berkman R, et al. Surface expression of Gp 165/95, the complement receptor CR3, as a marker of disease activity in systemic lupus erythematosus. Clin Immunol Immu-nopathol 1988;46:141-9.

Belmont HM, Abramson SB. Mechanisms of acute inf lam-

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mation and vascular injury in systemic lupus erythematosus. In: Wallace DJ, Hahn BH, eds. Dubois’ lupus erythematosus. 7th ed. Philadelphia: Lippincott Williams & Wilkins, 2007:236-54.

Lee-Kirsch MA, Gong M, Chowdhury D, et al. Mutations in the gene encoding the 3′-5′ DNA exonuclease TREX1 are associated with systemic lupus erythematosus. Nat Genet 2007;39:1065-7.

Richards A, van den Maagdenberg AM, Jen JC, et al. C-termi-nal truncations in human 3′-5′ DNA exonuclease TREX1 cause autosomal dominant retinal vasculopathy with cerebral leuko-dystrophy. Nat Genet 2007;39:1068-70.Copyright © 2008 Massachusetts Medical Society.

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Complexities of Prostate-Cancer RiskEdward P. Gelmann, M.D.

As men age, prostate epithelial cells are subject-ed to substantial stresses, and these stresses can damage DNA, thereby causing cellular transfor-mation. The aging prostate gland acquires numer-ous foci of cancer cells that arise from distinct clonal transformation events.1 That most of these foci never develop into clinically detectable can-cer is consistent with the frequent finding of prostate cancer during autopsies of asymptom-atic men in whom the condition was never diag-nosed.2

Susceptibility to prostate cancer has a clear heritable component: men are at an increased risk for the disease if they have a first-degree rela-tive with prostate cancer. The more relatives a man has with the disease, the greater his risk of prostate cancer.3 The hereditary aspect of prostate cancer, particularly in families in which the disease was diagnosed before the age of 60 years, led to genetic linkage studies that identi-fied several candidate tumor-suppressor genes. However, the role of some of these genes in causing cancer was not confirmed by subse-quent analyses. One gene that was identified in linkage studies, HPC1, codes for RNase-L pro-tein, a mediator of the action of interferon. RNase-L could affect carcinogenesis in the pros-tate because of its role in inflammation or by attenuating surveillance of infection by a gam-maretrovirus,4-6 but these possibilities are un-proven. Many of the other loci implicated by linkage analysis are limited to very few pros-tate-cancer kindreds.

The mapping of the human genome allows for genomewide association studies that reveal genetic determinants of disease on a much larger scale than do traditional linkage studies. Such studies have found a genetic influence in pros-

tate cancer, even in men without a family histo-ry. Single-nucleotide polymorphisms (SNPs) at three chromosomal loci — 8q24, 17q12, and 17q24.3 — have reproducibly scored as loci as-sociated with prostate cancer.7-9 However, the loci of these SNPs do not reside within or near identifiable genes. It has been hypothesized that they exist in regulatory regions of DNA that control gene expression. Such regions may con-tain enhancers that affect the transcription of remote genes on the same chromosome. Alter-natively, they could be in regions of DNA that code for microRNAs or other regulatory tran-scripts that influence the expression of genes on other chromosomes, the stability of messen-ger RNA, or even the fate of proteins. The three 8q24 loci are each independently linked to the risk of prostate cancer, and when more than one high-risk allele is present, the risk is magnified in proportion to the number of high-risk loci. These findings have important implications for elucidating the function of the three loci.

In this issue of the Journal, the study by Zheng et al.10 extends our knowledge of the genetic pre-disposition to prostate cancer by examining the association between prostate cancer and five SNPs that map to the three 8q24 loci, to 17q12, and to 17q24.3. The investigators first examined the pros-tate-cancer risk ratios for 16 polymorphic mark-ers at the three loci to determine which individual SNP was most strongly associated with prostate cancer for each locus. The risk ratios for the 16 SNPs ranged from 1.07 to 1.65. One SNP was chosen as most highly representative of each of the five high-risk loci. Individually, the risk ratios associated with these loci ranged from 1.22 to 1.53. When four or five high-risk genotypes were present, they were associated with a composite



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