A novel assay for serum complement activity: C42 generation assay.
BACKGROUND
In most clinics, laboratory tests for serum complement are limited to immunochemical determinations of C3 and C4 and are occasionally extended to the hemolytic titration of total complement functional activity (CH50). However, these tests are often not sufficient for the analysis of low CH50 serum.


METHODS
A novel assay for serum complement activity, the C42 generation assay, has been developed. The principle of this assay is based on the hemolysis of sensitized sheep erythrocytes (EA) by complement components in two sera: C42 (the classical pathway C3 convertase) is generated on EA by C1, C4 and C2 in the first serum, followed by a second reaction leading to hemolysis by C3-C9 supplied by the addition of the second serum in the presence of EDTA.


RESULTS
This methodology permits the evaluation of two distinct serum complement activities of a test serum. The combined activity of C1, C4 and C2, as well as the combined activity of C3-C9, can be estimated from the observed degrees of hemolysis. Information obtained from this assay is helpful for the analysis of test serum determined to have decreased CH50. Several clinical cases are presented in which this assay was utilized.


CONCLUSIONS
The C42 generation assay is another functional assay of serum complement which can provide information beyond that obtained from the typical serum CH50 assay. Since intermediate cells or isolated complement components are not necessary, this assay can be employed rapidly and economically in a clinical setting.
Kobayashi
E
E
Department of Medical Technology, Osaka Prefectural College of Health Sciences, Osaka, Japan.
Kitano
E
E
Kitamura
H
H
D000818:Animals; D003184:Complement C7 / Q000172:deficiency; D015941:Complement Hemolytic Activity Assay / Q000379:methods*; D003169:Complement Inactivator Proteins; D003170:Complement Pathway, Alternative; D003171:Complement Pathway, Classical; D003165:Complement System Proteins / Q000032:analysis*; D005069:Evaluation Studies as Topic; D015673:Fatigue Syndrome, Chronic / Q000276:immunology; D015432:Glomerulonephritis, Membranoproliferative / Q000276:immunology; D006461:Hemolysis; D019698:Hepatitis C, Chronic / Q000276:immunology; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000276:immunology; D012756:Sheep
D003184:Complement C7; D003169:Complement Inactivator Proteins; D003165:Complement System Proteins