Serum lymphocytotoxic activity in leprosy.

Area of Science:

• Immunology
• Dermatology
• Infectious Diseases

Background:

• Leprosy is a complex infectious disease spectrum with various clinical manifestations.
• Hypersensitivity reactions, including erythema nodosum leprosum (ENL) and Type I reactions, complicate leprosy management.
• The immunological basis of these reactions, particularly autoantibody involvement, requires further elucidation.

Purpose of the Study:

• To investigate the presence and characteristics of lymphocytotoxic activity (LCA) in leprosy patients.
• To correlate LCA with specific leprosy subtypes and hypersensitivity reactions.
• To identify the nature and potential targets of LCA in leprosy.

Main Methods:

• Screened sera from 167 leprosy patients and 46 controls for LCA using the Terasaki microdroplet lymphocytotoxicity assay.
• Performed assays at 37°C and 15°C against a diverse panel of lymphocytes representing HLA-ABC antigens.
• Characterized LCA by testing the effects of dithiothreitol, anti-IgM antiserum, immune complex removal, and rheumatoid factor.

Main Results:

• Elevated complement-dependent LCA at 15°C was observed in leprosy patients with histories of ENL or Type I reactions.
• Significantly higher LCA prevalence was found in lepromatous (86%), borderline lepromatous (83%), and borderline tuberculoid (88%) patients with reaction histories compared to controls (39%).
• LCA was attributed to IgM autoantibodies and reacted with both allogeneic and autologous lymphocytes, without specific HLA-ABC antigen targeting.

Conclusions:

• Leprosy patients experiencing hypersensitivity reactions exhibit increased IgM-mediated LCA.
• This LCA appears to be an autoantibody phenomenon, reacting broadly with lymphocytes.
• The precise role of these autoantibodies in the pathogenesis of leprosy hypersensitivity reactions warrants further investigation.