[Cell mediated immune response in leprosy lesions].

Area of Science:

• Immunology
• Dermatology
• Pathology

Background:

• Leprosy, a complex infectious disease, presents diverse clinical and immunological manifestations.
• Understanding the cellular immune response in different leprosy types is crucial for diagnosis and treatment.

Observation:

• Immunohistochemical analysis of biopsies from tuberculoid (TT) and polar lepromatous (LLp) leprosy patients revealed distinct cellular distributions.
• In TT leprosy, granulomas featured epithelioid cells and helper/inducer T cells (Leu 3a+) centrally, with suppressor/cytotoxic T cells (T8+) and B cells peripherally.
• LLp leprosy lesions showed a uniform admixture of helper/inducer T cells, suppressor/cytotoxic T cells, and macrophages, indicative of a suppressed immune response.

Findings:

• The cellular architecture in TT leprosy suggests a coordinated, cell-mediated immune response.
• The diffuse infiltration in LLp leprosy indicates a failure of the immune system to contain Mycobacterium leprae.
• Erythema nodosum leprosum (ENL) lesions in LLp patients showed increased helper/inducer cells and HLA-DR expression on keratinocytes, suggesting a potential role for cell-mediated immunity in ENL pathogenesis.

Implications:

• Distinct immunohistochemical patterns correlate with different leprosy classifications and immune statuses.
• Further research into the role of B cells and specific T cell subsets could refine understanding of granuloma formation in leprosy.
• Investigating the immune mechanisms in ENL reactions may lead to targeted therapeutic strategies for leprosy complications.