The complement system is part of the innate immune response and as such defends against invading pathogens, removes immune complexes and damaged self-cells, aids organ regeneration, confers neuroprotection, and engages with the adaptive immune response via T and B cells. Complement activation can either benefit or harm the host organism; thus, the complement system must maintain a balance between activation on foreign or modified self surfaces and inhibition on intact host cells. Complement regulators are essential for maintaining this balance and are classified as soluble regulators, such as factor H, and membrane-bound regulators. Defective complement regulators can damage the host cell and result in the accumulation of immunological debris. Moreover, defective regulators are associated with several autoimmune diseases such as atypical hemolytic uremic syndrome, dense deposit disease, age-related macular degeneration, and systemic lupus erythematosus. Therefore, understanding the molecular mechanisms by which the complement system is regulated is important for the development of novel therapies for complement-associated diseases.
Adaptive Immunity ; Antigen-Antibody Complex ; Autoimmune Diseases ; Autoimmunity ; B-Lymphocytes ; Complement Activation ; Complement Factor H ; Complement System Proteins* ; Glomerulonephritis, Membranoproliferative ; Hemolytic-Uremic Syndrome ; Immunity, Innate ; Lupus Erythematosus, Systemic ; Macular Degeneration ; Physiology* ; Regeneration

BACKGROUND: In vitro levels of complement C3 and C4 proteins are sensitive to storage conditions. To avoid in vitro complement activation when testing is delayed, serum should be frozen at -20degrees C within 2 hr of venipuncture. However, this is impractical in routine laboratory work. Therefore, we investigated alterations in C3 and C4 levels in refrigerated specimens over time and derived formulae to estimate initial levels of complement concentrations in delayed testing. METHODS: Ten fresh specimens were measured for C3 and C4 concentrations and were refrigerated at 4degrees C. We measured C3 and C4 levels in refrigerated samples daily for 4 days using an automated nephelometer (Beckman Coulter Inc., USA). RESULTS: C3 and C4 levels were significantly increased over time in refrigerated specimens (P<0.001, P<0.001, respectively). The increments in C3 and C4 levels were described by the equations: C3 (mg/dL)=3.55x+87.18 (r=0.9909), and C4 (mg/dL)=0.72x+22.3 (r=0.9395), where x=the number of days samples were refrigerated before testing. Increases in C3 and C4 concentrations were described on a percentage basis by the equations: DeltaC3 (%)=4.14x+1.07 (r=0.9903), and DeltaC4 (%)=3.57x+2.48 (r=0.9405). CONCLUSIONS: As the measured C3 and C4 concentrations increased by 3.55 mg/dL (4.1%) and 0.72 mg/dL (3.6%) per day in refrigerated specimens, the levels of C3 and C4 should be adjusted in delayed testing. We proposed that the formulae presented be used to back-calculate initial levels of C3 and C4 concentrations.
Complement Activation ; Complement C3* ; Complement C4 ; Complement System Proteins ; Phlebotomy

We report a case of hereditary angioedema in a 48-year old female patient. She experidenced facial edema and dyspnea 5 to 6 times for a year. Similar episodes developed on some members of her family, especially her sisters and father. We examined her and her sister's serum complement levels. The results showed decreased levels of C1 esterase inhibitor and C4, compared to normal levels. We treated the patient with danazol effectively.
Angioedemas, Hereditary* ; Complement C1 Inhibitor Protein ; Complement System Proteins ; Danazol ; Dyspnea ; Edema ; Fathers ; Female ; Humans ; Middle Aged ; Siblings

No abstract available.
Angioedema* ; Angioedemas, Hereditary* ; Complement C1 Inhibitor Protein* ; Complement C1s*

32 year-old male patient has experienced the repeated swelling of the skin on the eyelid, both hand, foot, lower and upper extrimities and testicle spontaneously without any trauma since 17 years old. This happening has subsided with or without treatment after 2-3 days. His great grandfather had suffered from the same events but grandfather or father or even his two brothers and one sister didn't have any swellings like him. Two days after this attack, he visited emergency room, his serum complement level was decreased such as C1q 9.7mg/dl (10-20mg/dl), C3 52mg/dl (55-120mg/dl), C4 4mg/dl (20-50mg/dl) measured by single radial immunodiffusion (SRID), but two weeks after full recovery, C1q 11.2mg/dl, C3 79mg/dl, C4 5mg/dl. The level of C1 esterase inhibitor was decreased upto 8.1 mg/dl (> 11 mg/dl) measured by nephlemeter(Mitshibishi Co., Japan). Now he is just under the close observation without androgen treatment because the attack of HAE(hereditary angioedema) happens much less and less severe after adolescence.
Adolescent ; Adult ; Angioedemas, Hereditary* ; Complement C1 Inhibitor Protein ; Complement System Proteins ; Emergency Service, Hospital ; Eyelids ; Fathers ; Foot ; Hand ; Humans ; Immunodiffusion ; Male ; Siblings ; Skin ; Testis

Meningococcal disease is not rarely associated with abnormalities of the complement system. We experienced a case of C9 deficiency with meningococcal meningitis from a 12-year-old girl. Identification of complement deficiency has implications for management, including family studies, prophylaxis, vaccination, and altered threshold for infection screening and treatment.
Child ; Complement C9* ; Complement System Proteins* ; Female ; Humans ; Mass Screening ; Meningitis ; Meningitis, Meningococcal* ; Neisseria meningitidis ; Vaccination

The complement system is known to be involved in the pathogenesis of the skin lesions in pernphigus vulgaris, bullous pemphigoid, dermatitis herpetiformis, epidermolysis bullosa acquisita, and systemic lupus erythematosus. Authors examined the skin specimens of each disease cases, who did not show any evidence of complement deficiency, to determine the deposition of complement components(C4, C3, Chb-9) and their inhibitors(C4bp, Factor H, S-protein) by modified direct immunofluorescence. We also looked at the staining pattern and localization, for further insights of their pathobiologic contributions in each disease. The findings of deposits of complement components up to C9, as well as inhibitor proteins at the primary histopathologic sites, in the majority of those cases, may indicate that the complement system, to certain extent, involves the inflamrnatory reactions in these diseases. The co-localization of C5b-9 and S-protein could be regarded as the consequence of in situ formation of SC5b-9 complexs or as the result of non-lytic adsorbed complexes of fluid phase SC5b-9. The pathologic role of the complement seems to depend mostly on the complement-fixing biologic property and the amount of the tissue bound immune complexes, which are often heterogeneous to different diseases and among different patients.
Antigen-Antibody Complex ; Complement Factor H ; Complement Membrane Attack Complex ; Complement System Proteins* ; Dermatitis Herpetiformis ; Epidermolysis Bullosa Acquisita ; Fluorescent Antibody Technique, Direct ; Humans ; Lupus Erythematosus, Systemic ; Pemphigoid, Bullous ; Skin ; Skin Diseases*

BACKGROUND: Molecular and genetic studies of the complement component C9 have never been reported in Korea. METHODS: We have checked the TaqI polymorphism of the C9 gene in 52 randomly selected adult Koreans. Southern blot analysis was carried out to detect the restriction fragment length polymorphism (RFLP) of the C9 gene. The fragments of human C9 cDNA were hybridized with the TaqI digested genomic DNA. RESULTS: The functional levels of complements in all subjects were measured at 84.4+/-3.8% by hemolytic assay, which indicates that the subjects have functionally normal complement systems. Fifty-four percent of the individuals were found to have the C9 genes that contain the constant fragments only. It seems that the undetected TaqI site may be located in the intron of the C9 gene. The silent mutation of C->T transversion was found in exon 1 of the C9 gene through polymerase chain reaction-single strand conformational polymorphism, but no mutation was found in exon 4 of the C9 gene. CONCLUSIONS: We could not find TaqI polymorphism in exons of the C9 gene in 52 Koreans.
Adult ; Blotting, Southern ; Complement C9 ; Complement System Proteins ; DNA ; DNA, Complementary ; Exons ; Humans ; Introns ; Korea ; Polymorphism, Restriction Fragment Length

Ten serum samples from the patient with bullous pemphigoid with the baseruent mernbrane zone autoantibody titers of 320 or greater were tested, by the method of in vitro complement immunofluorescence, for their ability to fix Factor B and properdin in addition to Clq, C4 and C3. Five samples yielded positive C3 and properdin staining reaciions while four samples demonstrated positive Factor B stainings. All ten samples yieled positive C3, C4 and Clq staining reactions, Heat inactivation or treatment of the complement source with EDTA, MG2-EGTA abolished both C3, properdin and Factor B staining in all ten cases. This result suggest that pemphigoid antibody will fix properdin and Factor B in addition to Clq, C4 and C3, a phenomenon explained by assembly of the C3b amplification mechanism following activation of the classical pathway of complement system.
Complement Factor B* ; Complement System Proteins ; Edetic Acid ; Fluorescent Antibody Technique ; Hot Temperature ; Humans ; Pemphigoid, Bullous* ; Properdin*

We experienced a living donor liver transplantation for a 26-month-old girl with complement factor H deficiency. Complement factor H is a plasma protein that regulates the activity of the complement pathway. Complement overactivity induced by complement factor H deficiency is associated with atypical hemolytic uremic syndrome. Liver transplantation can be the proper treatment for this condition. During the liver transplantation of these patients, prevention of the complement overactivation is necessary. Minimizing complement activation, through the use of modalities such as plasma exchange before the surgery and transfusion of fresh frozen plasma throughout the entire perioperative period, may be the key for successful liver transplantation in these patients.
Child, Preschool ; Complement Activation ; Complement Factor H* ; Complement System Proteins ; Female ; Hemolytic-Uremic Syndrome* ; Humans ; Liver Transplantation* ; Living Donors* ; Perioperative Period ; Plasma ; Plasma Exchange