| Component | Disease condition | Detection methods | Genetic basis |
| C1q, s | collagen vascular disease, SLE, bacterial infections | CH50, RID | Point mutations; acquired form due to C1q autoantibodies |
| C2 | Neisserial infections, respiratory infections, SLE (often symptomless) | CH50, RID, electrophoresis | type I: 28-bp deletion at exon/ intron
junction 6 leading to splicing error; linked to HLA -A25 -B18 -C2Q0 -C4A4,B2
-DR2;
type II: impaired C2 secretion |
| C3 | bacterial infections, glomerulonephritis | CH50, RID, electrophoresis | various independent point mutations in the C3 gene; 800bp deletion due to Alu repeat-induced mutation |
| C4A / B | collagen vascular disease, SSPE, autoimmune diseases (SLE, PBC, autoimmune hepatitis, scleroderma) | CH50, RID, SDS-PAGE | 1. Complete gene deletion; 2. Gene conversion (isotype change) 3. Nonexpression due to 2-bp insertion >> stop codon |
| C5 | recurrent Neisserial infections | CH50, RID | Point mutation >> stop codon |
| C6 | recurrent Neisserial infections | CH50, RID | partial deficiency: splice site mutation >> loss of exons 16 & 17 (3' truncation) |
| C7 | recurrent Neisserial infections | CH50, RID | various independent point mutations and 1-bp deletions >> stop codons, substitutions, splice site mutations; deletion of exons 7 and 8 |
| C8 | recurrent Neisserial infections | CH50, SDS-PAGE, separate occurrence of C8a-g and b deficiency | C8B gene: point mutation in exon 9 >> stop codon
(common); also other rare mutations
C8A gene: |
| C9 | recurrent Neisserial infections, SLE (often symptomless) | RID | Point mutations >> stop codon, Cystein substitution |
| Properdin | fulminant Neisserial infections, sepsis | AP50 | various point mutations causing stop codons, frame shifts and amino acid substitutions |
| Factor B | (only heterozygotes detected, clinically inapparent) | AP50, RID, electrophoresis | n.d. |
| Factor H | Neisserial infections, glomerulonephritis, hemolytic uremic syndrome (HUS) | AP50, RID, reduced C3 levels | 4-bp deletion >> stop codon,
point mutations >> Cystein subsitutions (impaired secretion) , stop codon |
| Factor I | meningitis, pyogenic infections | CH50, RID, reduced C3 levels | Evidence for Alu repeat-induced mutation |
| C1 Inhibitor | Hereditary angioneurotic edema (HANE) | function, reduced levels of C1,C4,C2 | various point mutations and small deletions, exon deletions due to Alu repeat recombinations; acquired autoimmune form |
| C8BP | Paroxysmal nocturnal hemoglobinuria (PNH) | acidic lysis of erythrocytes | GPI anchor defect |
| DAF | PNH | acidic lysis of erythrocytes | GPI anchor defect |
| CD59 | PNH | acidic lysis of erythrocytes | GPI anchor defect |
| CR3
(and LFA-1, gp 150,95) |
recurrent bacterial skin infections | FACS analysis | deficiency of common b chain LCAM-B |
| Footnotes: a CH50
- complement haemolytic activity; AP50 - alternative
pathway haemolytic activity;
RID - radial immunodiffusion; FACS - fluorescence-activated cell sorter |
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The Complement Genetics Homepage in Mainz: Complement Deficiencies ( last update: September 20, 2000)