Complement Deficiencies

Author: V. Dimov, M.D., Allergist/Immunologist and Assistant Professor at University of Chicago
Reviewer: S. Randhawa, M.D., Allergist/Immunologist and Assistant Professor at LSU (Shreveport) Department of Allergy and Immunology

Deficiencies of almost all complement components have been reported but most are very uncommon. C2 deficiency is most common, at 1:10,000.

Complement deficiencies (click to enlarge the image).

What is CH50?

All 9 components of classical pathway (C1-C9) are required for a normal CH50 value, which is 150 to 250 units/mL.

CH50 of 200 units/mL means that a serum sample diluted 1:200 lysed 50% of the antibody-coated sheep erythrocytes in the test mixture.


SLE is seen much more frequently with deficiency of C1q than any other complement

Terminal Complement Deficiency

Terminal complement deficiency is associated with disseminated Neisseria infections and may be associated with various autoimmune diseases. Lysis, not merely opsonization, is required to clear Neisseria infection. These patients have normal C3 levels.

Related Reading

Chapter 6: The Complement System, Part 1 and Part 2. Allergy and Immunology Review Corner: Chapter 6, Part 1 of Middleton’s Allergy Principles and Practice, 7th Edition, edited by N. Franklin Adkinson, et al. FIT Corner Q&A.
Mnemonics: Complement

Published: 08/29/2009
Updated: 08/29/2010

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