Immunoglobulins that bind to uncoated ELISA plate surfaces: Appearance in mice during infection with lactate-dehydrogenase-elevating virus and in human anti-nuclear antibody-positive sera

Abstract

Immunoglobulins present in the blood plasma of mice infected with lactate-dehydrogenase-elevating virus (LDV) were found to bind strongly in the presence of 0.05 % Tween 20 to the uncoated surfaces of wells of certain ELISA plates with previously recognized high protein-binding capacity. The binding was readily distinguishable from non-specific background binding of immunoglobulins present in normal mouse plasma. The binding components absorbed to protein A and had molecular weights in the 150–300 kDa range. Binding of the purified IgG fraction was progressively inhibited by increasing the concentration of Tween 20 in the diluent and by preincubation of the fraction at pH 3–4 for 10 min. The appearance of plate-binding IgM and IgG during LDV infection corresponded approximately with previously reported time courses of appearance of IgM- and IgG-containing circulating immune complexes and of specific IgM and IgG anti-LDV antibodies in LDV-infected mice. We conclude that complexes of IgG and IgM with LDV antigens have a much higher affinity for ELISA plates with high protein-binding capacity than uncomplexed immunoglobulins. Immune complexes did not significantly bind to ELISA plates with low protein-binding capacity, which, therefore, are suitable for measuring specific antiviral antibodies. Preliminary experiments with human anti-nuclear antibody-positive serum samples demonstrated markedly elevated non-specific binding of immunoglobulins to high-binding-capacity ELISA plates.