Lymphocyte-mediated cytotoxicity in isoniazid-associated hepatitis

Area of Science:

• Immunology
• Hepatology
• Pharmacology

Background:

• Isoniazid (INH) is a primary drug for tuberculosis treatment.
• INH-induced hepatitis is a known adverse effect.
• The immunologic mechanisms underlying INH hepatotoxicity are not fully understood.

Purpose of the Study:

• To investigate the release of lymphotoxin (LT) from peripheral blood lymphocytes in patients with INH-induced hepatitis.
• To assess the cytotoxic effects of these lymphocytes on murine hepatoma cells and fibroblasts.

Main Methods:

• Peripheral blood lymphocytes from patients with INH-induced hepatitis were stimulated with INH or isonicotinic acid (INA).
• Lymphotoxin release was measured using L929 fibroblast target cells.
• Cytotoxicity was assessed using a 3H-proline cytotoxicity assay on murine hepatoma (L1469) and L929 fibroblast cells.

Main Results:

• Evidence of LT release was observed in 5 out of 6 patients after stimulation.
• Preincubation of hepatoma cells with INH enhanced lymphocyte cytotoxicity in 5 out of 6 patients.
• Enhanced cytotoxicity was also observed against L929 fibroblasts, indicating potential lack of tissue specificity.

Conclusions:

• Peripheral blood lymphocytes from patients with INH-induced hepatitis can release LT upon stimulation.
• INH may enhance lymphocyte-mediated cytotoxicity against liver cells, contributing to hepatitis.
• The observed cytotoxicity against fibroblasts suggests a complex immunologic response that may not be entirely liver-specific.