Immunology

The cellular immune response in leprosy may be helpful in promoting healing and maintaining immunity to reinfection; it may be suppressed and allow unlimited bacterial proliferation and antigen production and the accompanying hypersensitivity may damage tissues, especially nerves. Antibodies in leprosy do not contribute to healing, but their role in protection against reinfection needs reconsideration. They contribute to tissue damage through the formation of immune complexes. Factors which affect the immune response include genes, previous exposure to wild Mycobacteria or BCG, a factor whose importance to tuberculosis and leprosy is only just becoming appreciated, and a variety of environmental and circumstantial factors ranging from stress to chemotherapy. The different susceptibility of different races to leprosy may prove to be due to a combination of these factors. For the clinician the most important features of the immune response in leprosy are those which determine the type of disease that the patient develops, the clinical features of the disease at that point on the spectrum, the stability or instability of his disease and the complications that he may encounter in terms of movement across the spectrum and reactions, the type of treatment he will need, and its duration, and the prognosis. For the population at risk in an endemic area, or for the contacts of an infectious case of imported disease, the most important features of the immune response are those which determine that the great majority will develop subclinical self-healing lesions and that only a very few will develop disease, and that of those that do develop disease the majority will be permanently cured if diagnosis is early and treatment is correctly taken and properly supervised.