Abstract
A simple and rapid Microenzyme-Linked Immunosorbent Assay (MELISA) has been developed for determination of anti-single and anti-double stranded DNA antibodies in humans using a combination of protain A-alkaine posphatase conjugates and single or double stranded DNA (ss or ds DNA)-coated polystyrene microplates. After 1 h treatment of the plates with 100 μl of poly-L-lysine (PLL) solution (50 μg/ml), an aliquot of the solution containing 100 ng ss or ds DNA (50 μl) was added to PLL-treated plates and evaporated at 37°C overnight to facilitate the adherance of ss or ds DNA to the plates. None specific binding of diluted test sera from patients with systemic lupus erthematosus (SLE) or from normal individuals to the PLL-coated plates was minimized by exposure of the plates for 1 h to Trisbuffered saline (pH 7.4) containing 0.01% bovine serum alubmin.
The present assay is advantageous over those reported so far as it saves time and antigen. Results are as followed: anti-ss DNA antibodies in SLE by MELISA were significantly higher than those of rheumatoid arthritis (RA) and of normal individuals, but no difference was seen between those of SLE and chronic active hepatitis (CAH), whereas anti-ds DNA antibodies in SLE were significantly higher than those of RA, CAH and normal individuals.
Correlation between antibody titers obtained by MELISA and by radioimmunoassay showed positive. Patients with SLE were devided into four groups: 1) patients with no complications, 2) patients with nephritis, 3) patients with central nervous system (CNS) disorder with convulsion and/or cerebrovascular lesion (CNS lupus, type I), and patients with psychosis (CNS lnpus, type II). Anti-ss DNA antibody titers among these four groups were of no significant difference, however anti-ds DNA antibody titers in the group of CNS lupus, type I were significantly higher than those of the others.
