The effect of toluidine blue and methylene blue in immunochemical reactions in vitro

Our observation that the effect of a patient's autoantibody with a potent antithrombin activity could be inhibited by toluidine blue and methylene blue led us to investigate the effect of these dyes in several immunochemical reactions in vitro. Both dyes reduced the titer or prevented the detection of IgG-specific single- and double-stranded DNA-binding antibodies and rheumatoid factors but did not reduce the titer of antinuclear factor and had no effect on detection of microsomal and thyroglobulin antibodies. These dyes did not aggregate or precipitate the immunoglobulins and their inhibitory effect in serum could be removed by dialysis of serum. The possible mechanism of action of these dyes in immunochemical reactions is discussed.