Complement: Measurement

Jonathan North, City Hospital NHS Trust, Birmingham, UK

Published online: October 2010

DOI: 10.1002/9780470015902.a0001279.pub3

The complement system comprises a group of serum proteins and cell membrane receptors that function primarily to fight infection. Clinically, measurement of complement pathway activity and individual component levels is of value in (i) cases of suspected immunodeficiency with deficiencies of soluble components, including lectins, and of receptors leading to particular patterns of infection and (ii) conditions that involve complement activation such as systemic lupus erythematosis and renal translantion. This article describes functional and immunochemical methods that can be established in-house or are available commercially. Until recently, measurement of complement in clinical situations has been aimed at identifying deficiency, of either level or function or activation. Mutations resulting in increased function have been identified for one component and this has opened a new area of research with clinical implications.

Key Concepts:

  • Correct sample collection and storage is essential for measurement of complement.
  • Immunochemical measurement of circulating complement components can be performed by commercial assays, usually ELISA.
  • Functional complement assays are required to detect deficiencies that do not affect immunochemical levels.
  • Functional complement assays require buffers that are of the correct ionic strength and provide the requisite ions as well as being of the correct pH.
  • Biosensor assays allow affinity and kinetic studies of complement component interaction.

Keywords: CH50; EA; ELISA; haemolytic assays

Figure 1. Schematic diagram of the activation pathways of the complement system. Components sharing lectin, protease or anaphylatoxin properties are highlighted. Fluid and solid phase inhibitors are not shown.
Figure 2. Log–log plot of y/(1–y) against volume of diluted serum in a CH50 assay. y=% lysis at each dilution of serum expressed as a decimal so at the point of 50% haemolysis, y/(1–y)=1. The volume of diluted serum to give 50% lysis is therefore shown by the vertical dotted line. This is the CH50. Redrawn from Whaley (1985, p. 102).
Figure 3. The number of functional molecules per cell (Z) is plotted against the serum dilution in a typical haemolytic titration of an individual complement component. The hypothesis that a single functional complement component can lead to cell lysis implies that the proportion of unlysed cells can give a value for Z from Z=–ln(1–y) where y=%lysis. When Z=1, y=62.3% (0.623 as a decimal) and the corresponding dilution contains one functional complement molecule per cell. The concentration of the component in this instance is given by y/x×1000 where y=distance along x-axis to the initial dilution and x=the distance along the x-axis to the x value that gives Z=1. Redrawn from Whaley (1985, p. 107).
Figure 4. Plot of the number of haemolytic sites (Z) against the incubation time at 30°C in a Tmax assay. Z=the number of heamolytic sites (–ln(1–y) where y=% lysis in each tube). Tmax is indicated by the arrow. Redrawn from Whaley (1985, p. 96).
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 References
    Cicardi M, Bergamaschini L, Cugno M et al. (1998) Pathogenic and clinical aspects of C1 inhibitor deficiency. Immunobiology 199: 366–376.
    Inoshita H, Matsushita M, Koide S et al. (2009) A novel measurement method for activation of the lectin complement pathway via both mannose-binding lectin (MBL) and L-ficolin. Journal of Immunological Methods 349(1–2): 9–17.
    Minchinton RM, Dean MM, Clark TR, Heatley S and Mullighan CG (2002) Analysis of the relationship between mannose-binding lectin (MBL) genotype, MBL levels and function in an Australian blood donor population. Scandinavian Journal of Immunology 56: 630–641.
    Pickering MC and Walport MJ (2000) Links between complement abnormalities and systemic lupus erythematosus. Rheumatology (Oxford) 39: 133–141.
    Ross SC and Denson P (1984) Complement deficiency states and infection: epidemiology, pathogenesis and consequences of Neisseral and other infections in an immune deficiency. Medicine 63: 243–273.
    Stengaard-Pedersen K, Thiel S, Gadjeva M et al. (2003) Inherited deficiency of mannan-binding lectin-associated serine protease 2. New England Journal of Medicine 349: 554–560.
    book Whaley K (ed.) (1985) Methods in Complement for Clinical Immunologists. Edinburgh: Churchill Livingstone.
 Further Reading
    book Dodd AW and Sims RB (eds) (1997) Complement. A Practical Approach. Oxford: Oxford University Press.
    book Kirschfink M (1998) "The clinical laboratory: testing the complement system". In: Rother K, Till GO and Hänsch GM (eds) The Complement System, 2nd revised edn, pp. 522–547. Berlin: Springer.
    book Morgan BP (ed.) (2000) Complement Methods and Protocols (Methods in Molecular Biology). Totowa: Humana Press.
    book Phimster GM and Whaley K (1990) "Measurement of complement". In: Gooi HG and Chapel H (eds) Clinical Immunology. A Practical Approach, pp. 81–109. Oxford: Oxford University Press.

Related Sub-Topics:

Diagnostics, Therapeutics and Methods | Complement
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Article Title: Complement: Measurement
 
How to Cite close
North, Jonathan(Oct 2010) Complement: Measurement. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0001279.pub3]