Autoantigenic histone epitopes: a comparison between procainamide- and hydralazine-induced lupus

Area of Science:

• Immunology
• Rheumatology
• Pharmacology

Background:

• Drug-induced lupus (DIL) is a condition mimicking systemic lupus erythematosus (SLE).
• Antihistone antibodies are biomarkers in SLE and some DIL cases.
• Procainamide and hydralazine are known to induce lupus-like syndromes.

Purpose of the Study:

• To compare the antihistone antibody profiles in patients with procainamide-induced lupus versus hydralazine-induced lupus.
• To investigate potential differences in the mechanisms by which these drugs induce autoimmunity.

Main Methods:

• Immunoblotting was used to assess serum binding to individual histones and histone fragments.
• Sera from 19 patients with DIL (9 procainamide, 10 hydralazine) were analyzed.

Main Results:

• Procainamide-induced lupus sera showed histone epitope binding patterns similar to spontaneous SLE.
• Hydralazine-induced lupus sera recognized a broader range of histones and distinct epitopes.
• Significant differences were observed in histone epitope recognition between the two drug-induced lupus groups.

Conclusions:

• Procainamide and hydralazine induce antihistone antibodies via distinct mechanisms.
• Differences in chromatin structural alteration by these drugs may contribute to varied autoimmune responses.
• Understanding these mechanisms can inform DIL diagnosis and management.