Mannose-binding lectin (MBL) is an innate immune system pattern recognition protein that kills a wide range of pathogenic microbes through complement activation. A substantial proportion of all human populations studied to date have MBL deficiency due to MBL2 polymorphisms, which potentially increases susceptibility to infectious disease. MBL binds numerous respiratory pathogens but the capsule of Streptococcus pneumoniae abrogates its efficient binding. Clinical studies in humans have shown that MBL deficiency appears to predispose to severe respiratory tract infection. A recent meta-analysis shows that MBL deficiency was associated with death in patients with pneumococcal infection after adjusting for bacteraemia and comorbidities. Human clinical studies have also shown associations between MBL deficiency and various less common respiratory infections. Intracellular infections like tuberculosis may be less common with MBL deficiency because of reduced opsonophagocytosis. Lung secretions contain small amounts of MBL that are potentially sufficient to activate complement, but their measurement is confounded by dilution inherent in collection techniques. Therefore, if this protein does play a role in pulmonary immunity it is presumably through prevention of haematogenous dissemination of respiratory pathogens while adding to mucosal defences. Ficolins are collectins that are structurally and functionally related to MBL and are either present in serum or expressed in tissues including the lung. Limited variation in serum levels of L- and H-ficolin result from the presence of FCN2 and FCN3 polymorphisms. Initial studies on the impact of FCN2 polymorphisms or low L-ficolin levels do not seem to show major associations with respiratory infection. MBL is being developed as a new immunotherapeutic agent for prevention of infection in immunocompromised hosts. The available literature suggests that it may also be of benefit in MBL deficient patients with severe pneumonia. This review concentrates on clinical associations between MBL deficiency and susceptibility to respiratory tract infection.
© 2009 S. Karger AG, Basel
- Complement system
- Infectious diseases
- Innate immunity
- Mannose-binding lectin
- Eisen DP, Minchinton RM: Impact of mannose-binding lectin on susceptibility to infectious diseases. Clin Infect Dis 2003;37:1496–1505.
- Roy S, Knox K, Segal S, Griffiths D, Moore CE, Welsh KI, Smarason A, Day NP, McPheat WL, Crook DW, Hill AV: MBL genotype and risk of invasive pneumococcal disease: a case-control study. Lancet 2002;359:1569–1573.
- Garcia-Laorden MI, Sole-Violan J, Rodriguez de Castro F, Aspa J, Briones ML, Garcia-Saavedra A, Rajas O, Blanquer J, Caballero-Hidalgo A, Marcos-Ramos JA, Her- nandez-Lopez J, Rodriguez-Gallego C: Mannose-binding lectin and mannose-binding lectin-associated serine protease 2 in susceptibility, severity, and outcome of pneumonia in adults. J Allergy Clin Immunol 2008;122:368–374, 374 e1–e2.
- Ip WK, Chan KH, Law HK, Tso GH, Kong EK, Wong WH, To YF, Yung RW, Chow EY, Au KL, Chan EY, Lim W, Jensenius JC, Turner MW, Peiris JS, Lau YL: Mannose-binding lectin in severe acute respiratory syndrome coronavirus infection. J Infect Dis 2005;191:1697–1704.
- Eisen DP, Dean MM, Boermeester MA, Fidler KJ, Gordon AC, Kronborg G, Kun JF, Lau YL, Payeras A, Valdimarsson H, Brett SJ, Ip WK, Mila J, Peters MJ, Saevarsdottir S, van Till JW, Hinds CJ, McBryde ES: Low serum mannose-binding lectin level increases the risk of death due to pneumococcal infection. Clin Infect Dis 2008;47:510–516.
- Dorfman R, Sandford A, Taylor C, Huang B, Frangolias D, Wang Y, Sang R, Pereira L, Sun L, Berthiaume Y, Tsui LC, Pare PD, Durie P, Corey M, Zielenski J: Complex two-gene modulation of lung disease severity in children with cystic fibrosis. J Clin Invest 2008;118:1040–1049.
- Super M, Thiel S, Lu J, Levinsky RJ, Turner MW: Association of low levels of mannan-binding protein with a common defect of opsonisation. Lancet 1989;2:1236–1239.
- Minchinton RM, Dean MM, Clark TR, Heatley S, Mullighan CG: Analysis of the relationship between mannose-binding lectin (MBL) genotype, MBL levels and function in an Australian blood donor population. Scand J Immunol 2002;56:630–641.
- Eisen DP, Dean MM, Thomas P, Marshall P, Gerns N, Heatley S, Quinn J, Minchinton RM, Lipman J: Low mannose-binding lectin function is associated with sepsis in adult patients. FEMS Immunol Med Microbiol 2006;48:274–282.
- Dean MM, Minchinton RM, Heatley S, Eisen DP: Mannose binding lectin acute phase activity in patients with severe infection. J Clin Immunol 2005;25:346–352.
- Stengaard-Pedersen K, Thiel S, Gadjeva M, Moller-Kristensen M, Sorensen R, Jensen LT, Sjoholm AG, Fugger L, Jensenius JC: Inherited deficiency of mannan-binding lectin-associated serine protease 2. N Engl J Med 2003;349:554–560.
- Terai I, Kobayashi K, Fujita T, Hagiwara K: Human serum mannose binding protein (MBP): development of an enzyme-linked immunosorbent assay (ELISA) and determination of levels in serum from 1,085 normal Japanese and in some body fluids. Biochem Med Metab Biol 1993;50:111–119.
- Seyfarth J, Garred P, Madsen HO: Extra-hepatic transcription of the human mannose-binding lectin gene (mbl2) and the MBL-associated serine protease 1–3 genes. Mol Immunol 2006;43:962–971.
- Gomi K, Tokue Y, Kobayashi T, Takahashi H, Watanabe A, Fujita T, Nukiwa T: Mannose-binding lectin gene polymorphism is a modulating factor in repeated respiratory infections. Chest 2004;126:95–99.
- Jambo KC, French N, Zijlstra EE, Gordon SB: AIDS patients have increased surfactant protein D but normal mannose binding lectin levels in lung fluid. Respir Res 2007;8:42.
- Fidler KJ, Hilliard TN, Bush A, Johnson M, Alton E, Geddes D, Klein N, Turner M, Davies J: Mannose-binding lectin is present in the infected airway: a possible pulmonary defence mechanism. Thorax 2009;64:150–155.
- Valdimarsson H, Stefansson M, Vikingsdottir T, Arason GJ, Koch C, Thiel S, Jensenius JC: Reconstitution of opsonizing activity by infusion of mannan-binding lectin (MBL) to MBL-deficient humans. Scand J Immunol 1998;48:116–123.
- Reading PC, Morey LS, Crouch EC, Anders EM: Collectin-mediated antiviral host defense of the lung: evidence from influenza virus infection of mice. J Virol 1997;71:8204–8212.
- Neth O, Jack DL, Dodds AW, Holzel H, Klein NJ, Turner MW: Mannose-binding lectin binds to a range of clinically relevant microorganisms and promotes complement deposition. Infect Immun 2000;68:688–693.
- Hamvas RM, Johnson M, Vlieger AM, Ling C, Sherriff A, Wade A, Klein NJ, Turner MW, Webster AD: Role for mannose binding lectin in the prevention of Mycoplasma infection. Infect Immun 2005;73:5238–5240.
- Garred P, Harboe M, Oettinger T, Koch C, Svejgaard A: Dual role of mannan-binding protein in infections: another case of heterosis? Eur J Immunogenet 1994;21:125–131.
- Polotsky VY, Belisle JT, Mikusova K, Ezekowitz RA, Joiner KA: Interaction of human mannose-binding protein with Mycobacterium avium. J Infect Dis 1997;175:1159–1168.
- Kuipers S, Aerts PC, van Dijk H: Differential microorganism-induced mannose-binding lectin activation. FEMS Immunol Med Microbiol 2003;36:33–39.
- Anders EM, Hartley CA, Reading PC, Ezekowitz RA: Complement-dependent neutralization of influenza virus by a serum mannose-binding lectin. J Gen Virol 1994;75:615–22.
- Swanson AF, Ezekowitz RA, Lee A, Kuo CC: Human mannose-binding protein inhibits infection of HeLa cells by Chlamydia trachomatis. Infect Immun 1998;66:1607–1612.
- Moller-Kristensen M, Ip WK, Shi L, Gowda LD, Hamblin MR, Thiel S, Jensenius JC, Ezekowitz RA, Takahashi K: Deficiency of mannose-binding lectin greatly increases susceptibility to postburn infection with Pseudomonas aeruginosa. J Immunol 2006;176:1769–1775.
- Davies J, Neth O, Alton E, Klein N, Turner M: Differential binding of mannose-binding lectin to respiratory pathogens in cystic fibrosis. Lancet 2000;355:1885–1886.
- Krarup A, Sorensen UB, Matsushita M, Jensenius JC, Thiel S: Effect of capsulation of opportunistic pathogenic bacteria on binding of the pattern recognition molecules mannan-binding lectin, L-ficolin, and H-ficolin. Infect Immun 2005;73:1052–1060.
- Brown JS, Hussell T, Gilliland SM, Holden DW, Paton JC, Ehrenstein MR, Walport MJ, Botto M: The classical pathway is the dominant complement pathway required for innate immunity to Streptococcus pneumoniae infection in mice. Proc Natl Acad Sci USA 2002;99:16969–16974.
- Kuhlman M, Joiner K, Ezekowitz RA: The human mannose-binding protein functions as an opsonin. J Exp Med 1989;169:1733–1745.
- Malhotra R, Sim RB, Reid KB: Interaction of C1q, and other proteins containing collagen-like domains, with the C1q receptor. Biochem Soc Trans 1990;18:1145–1148.
- Tenner AJ, Robinson SL, Ezekowitz RA: Mannose binding protein (MBP) enhances mononuclear phagocyte function via a receptor that contains the 126,000 M(r) component of the C1q receptor. Immunity 1995;3:485–493.
- Ghiran I, Barbashov SF, Klickstein LB, Tas SW, Jensenius JC, Nicholson-Weller A: Complement receptor 1/CD35 is a receptor for mannan-binding lectin. J Exp Med 2000;192:1797–1807.
- Neth O, Jack DL, Johnson M, Klein NJ, Turner MW: Enhancement of complement activation and opsonophagocytosis by complexes of mannose-binding lectin with mannose-binding lectin-associated serine protease after binding to Staphylococcus aureus. J Immunol 2002;169:4430–4436.
- Jack DL, Lee ME, Turner MW, Klein NJ, Read RC: Mannose-binding lectin enhances phagocytosis and killing of Neisseria meningitidis by human macrophages. J Leukoc Biol 2005;77:328–336.
- Brouwer N, Dolman KM, van Houdt M, Sta M, Roos D, Kuijpers TW: Mannose-binding lectin (MBL) facilitates opsonophagocytosis of yeasts but not of bacteria despite MBL binding. J Immunol 2008;180:4124–4132.
- Kronborg G, Weis N, Madsen HO, Pedersen SS, Wejse C, Nielsen H, Skinhoj P, Garred P: Variant mannose-binding lectin alleles are not associated with susceptibility to or outcome of invasive pneumococcal infection in randomly included patients. J Infect Dis 2002;185:1517–1520.
- Perez-Castellano M, Penaranda M, Payeras A, Mila J, Riera M, Vidal J, Pujalte F, Pareja A, Villalonga C, Matamoros N: Mannose-binding lectin does not act as an acute-phase reactant in adults with community-acquired pneumococcal pneumonia. Clin Exp Immunol 2006;145:228–234.
- Eisen DP, Stubbs J, Spilsbury D, Carnie J, Leydon J, Howden BP: Low mannose-binding lectin complement activation function is associated with predisposition to Legionnaires’ disease. Clin Exp Immunol 2007;149:97–102.
- Herpers BL, Ijzerman EPF, de Jong BAW, Bruin JP, Kuipers S, Lettinga KD, van Hannen EJ, Rjikers GT, van Velzen-Blad H, de Jongh BM: Low functional levels of mannose-binding lectin despite normal genotypes in Legionella pneumophila pneumonia. European Congress of Clinical Microbiology and Infectious Diseases, Munich, Germany, 2007.
- Rantala A, Lajunen T, Juvonen R, Bloigu A, Silvennoinen-Kassinen S, Peitso A, Saikku P, Vainio O, Leinonen M: Mannose-binding lectin concentrations, MBL2 polymorphisms, and susceptibility to respiratory tract infections in young men. J Infect Dis 2008;198:1247–1253.
- Hoal-Van Helden EG, Epstein J, Victor TC, Hon D, Lewis LA, Beyers N, Zurakowski D, Ezekowitz AB, Van Helden PD: Mannose-binding protein B allele confers protection against tuberculous meningitis. Pediatr Res 1999;45:459–464.
- Bellamy R, Ruwende C, McAdam KP, Thursz M, Sumiya M, Summerfield J, Gilbert SC, Corrah T, Kwiatkowski D, Whittle HC, Hill AV: Mannose binding protein deficiency is not associated with malaria, hepatitis B carriage nor tuberculosis in Africans. QJM 1998;91:13–18.
- Soborg C, Madsen HO, Andersen AB, Lillebaek T, Kok-Jensen A, Garred P: Mannose-binding lectin polymorphisms in clinical tuberculosis. J Infect Dis 2003;188:777–782.
- Selvaraj P, Narayanan PR, Reetha AM: Association of functional mutant homozygotes of the mannose binding protein gene with susceptibility to pulmonary tuberculosis in India. Tuber Lung Dis 1999;79:221–227.
- Soborg C, Andersen AB, Range N, Malenganisho W, Friis H, Magnussen P, Temu MM, Changalucha J, Madsen HO, Garred P: Influence of candidate susceptibility genes on tuberculosis in a high endemic region. Mol Immunol 2007;44:2213–2220.
- Selvaraj P, Jawahar MS, Rajeswari DN, Alagarasu K, Vidyarani M, Narayanan PR: Role of mannose binding lectin gene variants on its protein levels and macrophage phagocytosis with live Mycobacterium tuberculosis in pulmonary tuberculosis. FEMS Immunol Med Microbiol 2006;46:433–437.
- Kudo K, Sano H, Takahashi H, Kuronuma K, Yokota S, Fujii N, Shimada K, Yano I, Kumazawa Y, Voelker DR, Abe S, Kuroki Y: Pulmonary collectins enhance phagocytosis of Mycobacterium avium through increased activity of mannose receptor. J Immunol 2004;172:7592–7602.
- Ribeiro LZ, Tripp RA, Rossi LM, Palma PV, Yokosawa J, Mantese OC, Oliveira TF, Nepomuceno LL, Queiroz DA: Serum mannose-binding lectin levels are linked with respiratory syncytial virus (RSV) disease. J Clin Immunol 2008;28:166–173.
- Zhang H, Zhou G, Zhi L, Yang H, Zhai Y, Dong X, Zhang X, Gao X, Zhu Y, He F: Association between mannose-binding lectin gene polymorphisms and susceptibility to severe acute respiratory syndrome coronavirus infection. J Infect Dis 2005;192:1355–1361.
- Anders EM, Hartley CA, Jackson DC: Bovine and mouse serum beta inhibitors of influenza A viruses are mannose-binding lectins. Proc Natl Acad Sci USA 1990;87:4485–4489.
- Kase T, Suzuki Y, Kawai T, Sakamoto T, Ohtani K, Eda S, Maeda A, Okuno Y, Kurimura T, Wakamiya N: Human mannan-binding lectin inhibits the infection of influenza A virus without complement. Immunology 1999;97:385–392.
- Tang YW, Li H, Wu H, Shyr Y, Edwards KM: Host single-nucleotide polymorphisms and altered responses to inactivated influenza vaccine. J Infect Dis 2007;196:1021–1025.
- Kaur S, Gupta VK, Thiel S, Sarma PU, Madan T: Protective role of mannan-binding lectin in a murine model of invasive pulmonary aspergillosis. Clin Exp Immunol 2007;148:382–389.
- Madan T, Kaur S, Saxena S, Singh M, Kishore U, Thiel S, Reid KB, Sarma PU: Role of collectins in innate immunity against aspergillosis. Med Mycol 2005;43(suppl 1):S155–S163.
- Crosdale DJ, Poulton KV, Ollier WE, Thomson W, Denning DW: Mannose-binding lectin gene polymorphisms as a susceptibility factor for chronic necrotizing pulmonary aspergillosis. J Infect Dis 2001;184:653–656.
- Eisen DP, Dean MM, O’Sullivan MV, Heatley S, Minchinton RM: Mannose-binding lectin deficiency does not appear to predispose to cryptococcosis in non-immunocompromised patients. Med Mycol 2008;46:371–375.
- Granell M, Urbano-Ispizua A, Suarez B, Rovira M, Fernandez-Aviles F, Martinez C, Ortega M, Uriburu C, Gaya A, Roncero JM, Navarro A, Carreras E, Mensa J, Vives J, Rozman C, Montserrat E, Lozano F: Mannan-binding lectin pathway deficiencies and invasive fungal infections following allogeneic stem cell transplantation. Exp Hematol 2006;34:1435–1441.
- Kilpatrick DC, Stewart K, Allan EK, McLintock LA, Holyoake TL, Turner ML: Successful haemopoietic stem cell transplantation does not correct mannan-binding lectin deficiency. Bone Marrow Transplant 2005;35:179–181.
- Garred P, Pressler T, Madsen HO, Frederiksen B, Svejgaard A, Hoiby N, Schwartz M, Koch C: Association of mannose-binding lectin gene heterogeneity with severity of lung disease and survival in cystic fibrosis. J Clin Invest 1999;104:431–437.
- Drumm ML, Konstan MW, Schluchter MD, Handler A, Pace R, Zou F, Zariwala M, Fargo D, Xu A, Dunn JM, Darrah RJ, Dorfman R, Sandford AJ, Corey M, Zielenski J, Durie P, Goddard K, Yankaskas JR, Wright FA, Knowles MR: Genetic modifiers of lung disease in cystic fibrosis. N Engl J Med 2005;353:1443–1453.
- Muhlebach MS, MacDonald SL, Button B, Hubbard JJ, Turner ML, Boucher RC, Kilpatrick DC: Association between mannan-binding lectin and impaired lung function in cystic fibrosis may be age-dependent. Clin Exp Immunol 2006;145:302–307.
- Yang IA, Seeney SL, Wolter JM, Anders EM, McCormack JG, Tunnicliffe AM, Rabnott GC, Shaw JG, Dent AG, Kim ST, Zimmerman PV, Fong KM: Mannose-binding lectin gene polymorphism predicts hospital admissions for COPD infections. Genes Immun 2003;4:269–274.
- Hodge S, Hodge G, Jersmann H, Matthews G, Ahern J, Holmes M, Reynolds PN: Azithromycin improves macrophage phagocytic function and expression of mannose receptor in chronic obstructive pulmonary disease. Am J Respir Crit Care Med 2008;178:139–148.
- Vorup-Jensen T, Sorensen ES, Jensen UB, Schwaeble W, Kawasaki T, Ma Y, Uemura K, Wakamiya N, Suzuki Y, Jensen TG, Takahashi K, Ezekowitz RA, Thiel S, Jensenius JC: Recombinant expression of human mannan-binding lectin. Int Immunopharmacol 2001;1:677–687.
- Matsushita M, Endo Y, Taira S, Sato Y, Fujita T, Ichikawa N, Nakata M, Mizuochi T: A novel human serum lectin with collagen- and fibrinogen-like domains that functions as an opsonin. J Biol Chem 1996;271:2448–2454.
- Endo Y, Sato Y, Matsushita M, Fujita T: Cloning and characterization of the human lectin P35 gene and its related gene. Genomics 1996;36:515–521.
- Sugimoto R, Yae Y, Akaiwa M, Kitajima S, Shibata Y, Sato H, Hirata J, Okochi K, Izuhara K, Hamasaki N: Cloning and characterization of the Hakata antigen, a member of the ficolin/opsonin p35 lectin family. J Biol Chem 1998;273:20721–20727.
- Endo Y, Matsushita M, Fujita T: Role of ficolin in innate immunity and its molecular basis. Immunobiology 2007;212:371–379.
- Akaiwa M, Yae Y, Sugimoto R, Suzuki SO, Iwaki T, Izuhara K, Hamasaki N: Hakata antigen, a new member of the ficolin/opsonin p35 family, is a novel human lectin secreted into bronchus/alveolus and bile. J Histochem Cytochem 1999;47:777–786.
- Hummelshoj T, Fog LM, Madsen HO, Sim RB, Garred P: Comparative study of the human ficolins reveals unique features of Ficolin-3 (Hakata antigen). Mol Immunol 2008;45:1623–1632.
- Runza VL, Schwaeble W, Mannel DN: Ficolins: novel pattern recognition molecules of the innate immune response. Immunobiology 2008;213:297–306.
- Hummelshoj T, Munthe-Fog L, Madsen HO, Fujita T, Matsushita M, Garred P: Polymorphisms in the FCN2 gene determine serum variation and function of Ficolin-2. Hum Mol Genet 2005;14:1651–1658.
- Munthe-Fog L, Hummelshoj T, Ma YJ, Hansen BE, Koch C, Madsen HO, Skjodt K, Garred P: Characterization of a polymorphism in the coding sequence of FCN3 resulting in a Ficolin-3 (Hakata antigen) deficiency state. Mol Immunol 2008;45:2660–2666.
- Kilpatrick DC, Fujita T, Matsushita M: P35, an opsonic lectin of the ficolin family, in human blood from neonates, normal adults, and recurrent miscarriage patients. Immunol Lett 1999;67:109–112.
- Cedzynski M, Nuytinck L, Atkinson AP, St Swierzko A, Zeman K, Szemraj J, Szala A, Turner ML, Kilpatrick DC: Extremes of L-ficolin concentration in children with recurrent infections are associated with single nucleotide polymorphisms in the FCN2 gene. Clin Exp Immunol 2007;150:99–104.
- Atkinson AP, Cedzynski M, Szemraj J, St Swierzko A, Bak-Romaniszyn L, Banasik M, Zeman K, Matsushita M, Turner ML, Kilpatrick DC: L-Ficolin in children with recurrent respiratory infections. Clin Exp Immunol 2004;138:517–520.
- Chapman SJ, Vannberg FO, Khor CC, Segal S, Moore CE, Knox K, Day NP, Davies RJ, Crook DW, Hill AV: Functional polymorphisms in the FCN2 gene are not associated with invasive pneumococcal disease. Mol Immunol 2007;44:3267–3270.
- Kolble K, Lu J, Mole SE, Kaluz S, Reid KB: Assignment of the human pulmonary surfactant protein D gene (SFTP4) to 10q22–q23 close to the surfactant protein A gene cluster. Genomics 1993;17:294–298.
- Sorensen GL, Petersen I, Thiel S, Fenger M, Christensen K, Kyvik KO, Sorensen TI, Holmskov U, Jensenius JC: Genetic influences on mannan-binding lectin (MBL) and mannan-binding lectin associated serine protease-2 (MASP-2) activity. Genet Epidemiol 2007;31:31–41.
Dr. Damon P. Eisen
Victorian Infectious Diseases Service
Royal Melbourne Hospital
Grattan St, Parkville, Victoria, VIC 3050 (Australia)
Tel. +61 3 9342 7212, Fax +61 3 9342 7277, E-Mail email@example.com
Received: October 21, 2008
Accepted after revision: December 3, 2008
Published online: July 7, 2009
Number of Print Pages : 9
Number of Figures : 1, Number of Tables : 1, Number of References : 80
Journal of Innate Immunity
Vol. 2, No. 2, Year 2010 (Cover Date: February 2010)
Journal Editor: Herwald H. (Lund), Egesten A. (Lund)
ISSN: 1662-811X (Print), eISSN: 1662-8128 (Online)
For additional information: http://www.karger.com/JIN
Copyright / Drug Dosage / Disclaimer
Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher or, in the case of photocopying, direct payment of a specified fee to the Copyright Clearance Center.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in goverment regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.