R. Suenaga et Ni. Abdou, HEPARAN-SULFATE ELISA GIVES FALSE-POSITIVE RESULTS FOR ANTI-DNA DNA HISTONE IMMUNE-COMPLEXES IN SERA OF PATIENTS WITH SLE, Lupus, 4(1), 1995, pp. 57-62
Heparan sulphate-reactive antibodies in lupus sera have been suggested
to be anti-DNA-DNA/histone immune complexes and to be associated with
lupus nephritis. In this study, 23 anti-DNA-positive lupus sera inclu
ding 13 active nephritis sera were tested for the presence of circulat
ing anti-DNA-DNA/histone immune complexes by solid phase heparan sulph
ate-ELISA. Because of high background binding to protamine chloride-li
nked heparan sulphate plates, poly-L-lysine (PLL) was used as a linker
and the remaining active sites of PLL were blocked with poly-L-glutam
ic acid. The ELISA was capable of detecting small amounts of anti-DNA
IgG-DNA/histone immune complexes formed in vitro. However, only three
active nephritis sera of the 23 sera tested showed significant binding
to heparan sulphate plates. This binding was found to be non-specific
, the result of high background binding of IgG to PLL. Anti-heparan su
lphate ELISA using positively charged linkers detects non-specific bin
ding when lupus sera are tested. Specific assays need to be developed
for DNA/histone-related immune complexes present in lupus sera.