COUNTERIMMUNOELECTROPHORESIS WITH SERUM PREDIFFUSION - AN IMPROVED METHOD FOR THE DETECTION AND IDENTIFICATION OF ANTIBODIES AGAINST EXTRACTABLE NUCLEAR AND CYTOPLASMIC ANTIGENS

In the technique of counterimmunoelectrophoresis (CIE) with serum pred iffusion (SPD) serum is allowed to diffuse freely into the gel before pouring the antigenic extract in its trough (or wells) and starting th e electrophoresis. Both the immunoprecipitations and the interactions with reference sera are strongly intensified by SPD, leading to higher sensitivity and specificity for the detection of anti-SSA/Ro, anti-SS B/La, anti-U1RNP, anti-Sm, anti-Jo1 and even anti-Scl-70 antibodies. W e found that the optimal SPD time was 2 h. To evaluate the relevance o f SPD for the clinical laboratory, 92 antinuclear antibody (ANA) posit ive sera were tested on CIE without SPD and with 2 h SPD in identifica tion tests with SSA/Ro, SSB/La, Sm, U1RNP and Jo1 reference sera (rsa) , The precipitation lines and their interactions were evaluated by thr ee independent observers. It was observed that SPD considerably improv ed the efficiency of CIE for antibody identification, The mechanisms u nderlying the intensification of the precipitation lines by SPD are di scussed as are the characteristics of the CIE in comparison with other test systems such as the enzyme linked immunosorbent assay (ELISA) an d immunoblot.