Measurement of DNA antibodies by double antibody precipitation.

Antibodies to nuclear constituents particularly to native deoxyribonucleic acid (DNA) have been detected in the serum and tissues of patients with systemic lupus erythematosus (SLE) and may be involved in the pathogenesis of the disease when deposited as immune complexes (Tan, Schur, Carr, and Kunkel, 1966). The methods used for the detection in serum included immunoprecipitation (Seligmann, 1957) and complement fixation (Ceppellini, Polli, and Celada, 1957). More recently an isotope-labelled DNA-binding technique (Wold, Young, Tan, and Farr, 1968) has provided an assay which is of considerably increased sensitivity and has become a widely used method of demonstrating DNA antibodies (Pincus, Schur, Rose, Decker, and Talal, 1969; Hughes, Cohen, and Christian, 1971). However, this assay has certain inherent problems in the separation of bound from free antigen which led us to examine the use of immunoprecipitation with an anti-human gamma globulin. This communication describes a method using a double or second antibody.