Antibodies to nucleoprotein and to hydrazide-altered soluble nucleoprotein in tuberculous patients receiving isoniazid

Abstract

Antibodies to calf thymus nuclei, nucleoprotein, DNA, soluble nucleoprotein and hydrazide (hydrallazine and isoniazid)-altered nucleoprotein were investigated by a standard complement-fixation method in 214 tuberculous patients receiving isoniazid. Findings were compared to those on thirty-seven sera from lupus patients receiving neither steroids nor immunosuppressants and on sixty-six sera from normal controls.

The incidence of antibodies to all antigens studied except DNA was significantly higher in isoniazid-treated tuberculous patients than in the normal controls, but lower than in the lupus patients. Unlike lupus there were no detectable DNA antibodies in the tuberculous or in the control sera. Antibodies to nucleoprotein (soluble and insoluble) and particularly to hydrazide-altered nucleoprotein were the most frequently found in the isoniazid-treated tuberculous patients. In general, antinuclear antibodies were more frequent in the isoniazid-treated tuberculous female than in the male; in the adult than in the child.

It is suggested that hydrazides may cause in vivo similar alteration of nucleoprotein to that which they cause in vitro. Hydrazide-altered nucleoprotein probably elicits the production of antinuclear antibodies which in turn may activate systemic lupus erythematosus in otherwise predisposed individuals.