Circulating cytokine profiles in leprosy patients.

BACKGROUND Leprosy is a chronic infectious disease caused by Mycobacterium leprae which is an obligate intracellular pathogen. It is characterised by a broad spectrum of clinical forms dictated by the patient's immune response to the organism. The tuberculoid pole has good cell mediated immunity to M. leprae, with few lesions and bacilli while the lepromatous pole has poor immunity coupled with extensive involvement and greater bacillary load. METHODS We studied serum levels of interferon gamma and interleukin 6 in 100 patients of untreated leprosy, compared them with 30 age and sex matched normal healthy controls and co-related them with different parts of the spectrum and reactional episodes. The purpose of this study was to delineate the role of cytokines and their clinical implications in the leprosy spectrum and during reactional episodes. RESULTS We observed that mean cytokine levels were significantly higher in the patient group as compared to the controls. In the non reactional patient group, pure neuritic leprosy patients showed highest levels of INFgamma which were directly proportional to the extent of nerve involvement. Lepromatous leprosy patients had the highest levels of IL6. Bacteriological index demonstrated a negative and positive corelation with INFgamma and IL 6 levels respectively. Type I and Type II reactional patients had higher levels of INFgamma and IL 6 respectively as compared to nonreactional patients. CONCLUSIONS Our results suggest that pure neuritic leprosy and borderline tuberculoid patients in type I reaction are at greatest risk for nerve and tissue damage. Thus cytokines have the potential to play a significant role in classification, prognosis and treatment of leprosy.