Immunoelectrophoretic 'tailing' of albumin line due to albumin-IgG antibody complexes: a side effect of nitrofurantoin treatment?

The immunochemical analysis of sera of 10 patients in which immunoelectrophoresis showed a cathodic, elongated, 'tailing' albumin (TA) line is described. Eight of the 10 patients had been treated with nitrofurantoin, and withdrawal of the drug was followed by disappearance of the phenomenon in 5 cases. Most of the patients had polyclonally elevated IgG and IgA levels and a decreased albumin level; IgM; C3, C4, and C1-INH were normal. Antinuclear activity of IgG type was demonstrated in the sera of 9 patients. The TA phenomenon was due to noncovalently bound complexes between IgG and albumin. The combining sites of the IgG molecules were in the Fab fragment. The antibody-like activity of the IgG was directed towards autologous albumin. The anti-albumin activity remained unchanged after absorption of the antinuclear activity. The nitrofurantoin-induced albumin-anti-albumin system may prove useful as a human model of autoimmune response of known aetiology.