Microhemagglutination test for the detection of nucleoprotein antibody in systemic lupus erythematosus

A simple and practical microhemagglutination test that detects two antibodies, one showing reactivity to the DNA moiety of soluble nucleoprotein (sNP) and the other to the DNA-histone complex of sNP, is described. The method incorporates human erythrocytes formalinized at 30 C., tanned, and coated with sNP at 37 C. Antibody specificity was determined by inhibition experiments performed on sera with added DNA or sNP antigen. With the indirect LE cell technic, evidence that the anti-sNP antibody detected in this work is related to the serum LE factor commonly associated with the LE cell phenomenon was obtained. The hemagglutination test is helpful in establishing the specific diagnosis of systemic lupus erythematosus (SLE) and may be used to follow the course of the disease and response to therapy in SLE patients, as this is a semiquantitative technic and rise or fall in titer or antibody can be determined.