Some immunological aspects of leprosy - abstract

ABSTRACT

Most cases of leprosy belong to two very contrasting types of the disease - the lepromatous and the tuberculoid. The lepromatous type is usually lepromin test negative, whereas the tuberculoid type is generally lepromin test positive. It is generally accepted that lepromin test positive individuals rarely develop leprosy and if they do, the disease is mild and the prognosis relatively good. There is some evidence that tuberculosis or B.C.G. vaccination produces conversion from lepromin negativity to lepromin positivity. This has been explained on the basis of a cross-immunity between leprosy and tuberculosis and has led French and South American workers to advocate B.C.G. vaccination as a means of leprosy control. In view of the above statements the specific problem at present under review is the answer to the following question- Does the allergic response of the host's tissues determine the type of leprosy or does the type of leprosy determine the allergic response? RESULTS (Preliminary investigations) 1. Tuberculin Test 53 percent(57/108) were tuberculin positive. In Jamaica generally, tuberculin positivity (all ages) is about 50 percent. 2. Histology of positive tuberculin reactions Twelve patients were studied (7 lepromatous, 3 tuberculous and 2 indeterminate). (a) All showed acute reaction consisting of oedema, focal haemorrhage and tissue necrosis and also a granulomatous infiltration of mononuclear cells. Five showed marked vesication. (b) Four of the lepromatous type showed a lepromatous reaction (isopathic phenomenon) in that the macrophage cells contained acid-fast bacilli and fat. CONCLUSIONS (Provisional) Clinically (and histologically about 50 percent of the patients were found to be sensitive to tuberculo-protein. If this sensitivity is due to tuberculosis (and the incidence is the same as in the general populace), the result suggests that there is little evidence of cross-immunity between tuberculosis and leprosy. Histologically, 4/7 lepromatous cases biopsied showed an isopathic phenomenon which may indicate that the type of leprosy influences the allergic response (AU)