The use of solid phase clq and horseradish peroxidase-conjugated goat anti-IgG for the detection of immune complexes in human serum

An alternative method is described for detecting immune complexes in human serum. The technique uses peroxidase-conjugated goat anti-human IgG to detect immune complexes bound to solid phase Clq † † Clq is a subcomponent of Cl, the first component of complement: C l r̄ and C l s̄, activated forms of the other two subcomponents of Cl; EAC4, rabbit antibody sensitized sheep erythrocytes bound to C4, the fourth component of complement; C2, second component of complement; CEDTA, whole complement diluted in 0.01 M EDTA; HAG, heat-aggregated IgG; PBS, phosphate buffered saline; ELISA, enzyme linked immunoadsorbent assay; SLE, systemic lupus erythematosus. Complement nomenclature is the recommendation of Bull. W.H.0. 39, 935, 1968. . The level of immune complexes is determined by reference to a standard curve constructed with heat-aggregated IgG. The assay is sensitive, detecting 10–10,000 ng of heat-aggregated IgG. Exogenous Clq (5–100 μg/ml) and heparin (5–500 μg/ml) do not interfere with the assay. Data are presented which show the levels of immune complexes in 79 normal individuals and 25 patients with systemic lupus erythematosus.