Patterns of antinuclear antibodies and lupus-activating drugs

Patterns of antinuclear antibodies (ANA) occurring in individuals consuming lupus-activating drugs who have not developed systemic lupus erythematosus (SLE), may give insight into their mode of action as SLE triggering agents. We have studied the antigenic specificity of ANA induced by isoniazid (INH), anticonvulsants and chlorpromazine. ANA found in INH treated subjects are primarily directed at soluble nucleoprotein (sNP), an antigen which is physicochemically altered in vivo by INH. Antibodies to INH altered sNP were found in 78 per cent of 214 subjects receiving INH, while none had anti-DNA antibodies. Different anticonvulsants give rise to different patterns of ANA. Antibodies to Sm antigen were found only in patients receiving hydantoins. Antibodies to native and denatured DNA were found in 14 per cent and 22 per cent respectively, of 170 patients receiving anticonvulsants. Antibodies to denatured DNA were most frequently found in patients receiving chlorpromazine, which correlated with the known reactivity of this drug to denatured DNA.