Radioimmunoassay for anticollagen--antibodies using 14C-labelled collagen

A sensitive radioimmunoassay for anticollagen antibodies is described. 14C-labelled human acid-soluble collagen of high specific activity (5 X 10(6) dpm/mg) is used as antigen either in native or denatured state. Experimentally induced anticollagen antibodies or RA synovial fluids containing antibodies to collagen are reacted with the labelled antigen. The immune complexes formed are precipitated with goat antiserum to rabbit globulins ('second antibody'). A systematic investigation of the labelled collagen in regard to cleavage by enzymes, fibril formation and specificity showed that no gross alteration had been caused by the labelling procedure. The assay furnishes information on the avidity, specificity and immunoglobulin class of experimental or pathological anticollagen antibodies. It can also be used as sensitive assay for collagen in biological fluids.