C1q binding and C1q deviation assays using enzyme labelled C1q

Methods for the enzyme labelling of C1q are described. The C1q conjugates have been incorporated into suitably modified C1q deviation and C1q binding assays for circulating immune complexes. These assays show the expected high positivity rate in sera from patients with systemic lupus erythematosus. The assays using enzyme labelled C1q confer considerable advantages over their counterparts using 125I.