An update on the the lectin pathway of complement

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1 An update on the the lectin pathway of complement Laboratory of Molecular Medicine Department of Clinical Immunology, Section 7631 Rigshospitalet Copenhagen Denmark Malmø, September 17, 2012 Classical pathway Lectin pathway Alternative pathway Ag:antibody complex Carbohydrate structures Pathogen surfaces Complement activation Recruitment of inflammatory cells Opsonization of pathogens Killing of pathogens 1

2 Lectin pathway attack MASPs C4,C2 C3 MASPs C5a C9 C4bC2b C3b C3b C5b-8 Microorganism or altered self cell Membrane attack complex Characteristics of the lectin pathway initiators Synonyms CL-11 MBL Ficolin-1 Ficolin-2 Ficolin-3 Collectin-11 CL-K1 Mannose-binding lectin M-Ficolin P35 related antigen L-Ficolin EBP-37 Hucolin P35 H-Ficolin Hakata antigen Thermolabile β2- macroglycoprotein Gene name COLEC11 MBL2 FCN1 FCN2 FCN3 Gene location 2p q11-q21 9q34 9q34 1p36 Tissue expression Ubiquitously Liver Myeloid cells Liver Liver /lung Binding specificity Fucose Mannose GlcNAc Mannose GlcNAc Acetylated groups Sialic acid GlcNAc Acetylated groups N-acetyllactosamine Acetylated groups Plasma conc. (µg/ml)

3 Models of lectin pathway activation. Héja D et al. PNAS 2012;109: by National Academy of Sciences MASPs: 2 genes, 5 gene products MASP1 gene (chromosome 3q27-q28) MASP-1 (MASP1 isoform 1) activates MASP-2 cleaves C2 cleaves fibrinogen to fibrin, activates fxiii cleaves high molecular weight kininogen to bradykinin activates PAR4 on endothelial cells MASP-3 (MASP1 isoform 2) cleaves insulin-like growth factor binding protein 5 in vitro function unknown MAP-1 (MAp44) (MASP1 isoform 3) inhibits lectin pathway complement activation and thrombogenesis function unknown MASP2 gene (chromosome 1p36.3-p36.2) MASP-2 (MASP2-isoform 1) cleaves C4 and C2 to generate convertase C4bC2a cleaves prothrombin to thrombin smap (MAp19) or MAP-2 (MASP2 isoform 2) function unknown 3

4 3MC syndrome=mingarelli, Malpuech, Michels and Carnevale syndromes Characteristic facial and cranial dysmorphism, cleft lip and/or palate, learning disability and genital, limb and muscle abnormalities and many more 4

5 What about ficolin-3? History of Ficolin Epstein and Tan and 1978 Inaba and Okuchi Discovers the HAKATA ANTIGEN present in all human sera, (more than Japanese and Swedes investigated), which reacts with an autoantibody present in sera from some SLE patients The HAKATA ANTIGEN disappears during SLE disease flares associated with complement activation and is normalized during remission 5

6 Activation of the lectin complement pathway C4 deposition (OD490nm) Ficolin-1 Ficolin-2 Ficolin-3 MBL Ficolin/MBL (µg/ml) Hummelshøj et al Ficolin-3 serum concentration in healthy donors 50 Ficolin-3 µg/ml Munthe-Fog et al

7 Variation of FCN3 (FCN3+1637delC - FCN3 L117fs) Ficolin-3 multimer FCN3 WT FCN3 L117fs Allele frequency 0.01, homozygosity expected in 1:10,000 Hummelshøj, Munthe-Fog et al NEJM, 360: ,

8 Search for FCN3 deletion variant in patients with suspected immunodeficiencies A total of 1282 patients referred to Department of Clinical Immunology over a period of 12 years for routine immunologic investigation of various immunodeficiencies (not HIV related) Sequencing of exon 5 of FCN3 in all 1282 patients Munthe-Fog, Hummelshøj, Honoré et al., 2009, NEJM Genotyping of 1282 patients with suspected primary immunodeficiencies 40 P < Ficolin-3 µg/ml C/C n=115 C/- n=23 -/- n=1 Allele frequency of minor allele = homozygous patient Munthe-Fog, Hummelshøj, Honoré et al. NEJM,

9 Serum Ficolin-3 of index patient and the family kda S S M F Pt C Rec Polyclonal anti-ficolin-3 Ab Reduced Unreduced kda S S M F Pt C Rec Lanes 1: Heterozygous sister 2: Wild-type sister 3: Heterozygous mother 4: Heterozygous father 5: Index patient 6: Wild-type control 7: Wild-type rficolin-3 Munthe-Fog, Hummelshøj, Honoré et al., NEJM, 2009 Medical history of index patient 32-years old man (unrelated parents of Macedonian/Albanian origin) Since early childhood Repeated lower respiratory tract infections Since age 17 Recurring warts on his fingers Age 20 Spleen removed because of unexplained thrombocytopenia Age 26 Treated for bilateral frontal cerebral abscesses with non-hemolytic streptococci Since age 26 Several episodes of bacterial pneumonia requiring hospital admission Severe bronchiectasis and pulmonary fibrosis Progressively decreased lung capacity and obstructive lung disease Munthe-Fog, Hummelshøj, Honoré et al., NEJM

10 Possible consequences of Ficolin-3 deficiency Ficolin receptor? Normal cell Phagocytosis Phagocyte Dying cell complement activation via associated serine proteases (MASPs) Clearance of Cellular debris 10

11 Ficolin-3 specific complement activation ELISA MASPs Complement activation AcBSA Ficolin-3 binding to acetylated compounds Hein et al. 2010, PLoS ONE Ficolin-3 specific complement activation ELISA Hein et al. 2010, PLoS ONE 11

12 Lectin pathway Five recognition molecules exist MBL, CL-11, ficolin-1, ficolin-2 and ficolin-3 Two genes encodes 5 MASP gene products MASP-1, MASP-2, MASP-3, MAP-1 and smap Lectin pathway activates complement, coagulation and kallikrein systems Ficolin-3 is the most abundant and most powerful molecule in the human lectin pathway 12