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Inside the skin: the local immune and inflammatory milieu in leprosy
1Department of Pathology, John A. Burns School of Medicine, Honolulu, HI 96816.
Insights
Leprosy skin lesions reveal immune system balance. Introducing lymphokines can temporarily alter this balance, impacting disease presentation.
Area of Science:
- Immunology and Molecular Biology of Infectious Diseases
- Dermatology and Mycobacterial Pathogenesis
Background:
- Leprosy exhibits a broad spectrum of human immune responses to Mycobacterium leprae.
- Skin lesions are critical sites for understanding these diverse immune mechanisms.
Purpose of the Study:
- To investigate the immunologic equilibrium within leprosy skin lesions.
- To explore the impact of exogenous lymphokines on lesion immunology and histology.
Main Methods:
- Immunohistologic analysis of skin biopsies from leprosy lesions.
- Assessment of immune cell subsets and soluble immune mediators.
- Inoculation of exogenous lymphokines into lesions to observe effects.
Main Results:
- A low-level immunologic equilibrium exists in established lesions across the leprosy spectrum.
- Different proportions of T-helper and T-suppressor cells are present, yet overall activity is similar.
- Exogenous lymphokines can transiently modify this equilibrium and alter lesion histology.
Conclusions:
- Leprosy lesions maintain a delicate immunologic balance.
- Immune responses in leprosy reactions can spontaneously shift T cell subsets and lymphokine levels.
- Targeted lymphokine therapy may offer a means to modulate immune responses in leprosy.
Abstract:
Skin lesions of leprosy have become a rich source of new information about the mechanisms involved in the uniquely broad spectrum of human responsiveness to M. leprae. Recent technological advances in immunology and molecular biology have been applied to the study of skin lesions using 3 approaches: immunohistologic studies of skin biopsies from leprosy lesions, correlated assessment of cell subsets and soluble immunologic mediators, and studies of the effects of the inoculation of exogenous lymphokines into the lesions. Results from these studies suggest that an immunologic equilibrium may exist among long-established lesions across the spectrum so that, although T-helper and -suppressor cells are present in different proportions, immunologic activity is at a low, similar level in all types of lesions. Exogenous lymphokines can alter this equilibrium and temporarily change the histologic picture. Spontaneous immunologic changes occurring in acute leprosy reactions may also lead to changes in T cell subsets and quantities of lymphokines.